Impact of Definitive Chemoradiation on Quality-of-Life Changes for Patients With Anal Cancer: Long-term Results of a Prospective Study.

BACKGROUND: Maintaining and improving quality of life (QOL) are important goals of anal cancer management. This disease is generally curable, with many long-term survivors. OBJECTIVE: Long-term QOL after chemoradiation for patients with anal cancer was evaluated. DESIGN: This was a prospective cohort study. SETTINGS: This study used data from a prospective study of patients with anal cancer who were treated with chemoradiation between 2008 and 2013. PATIENTS: Patients with anal cancer who were treated with image-guided intensity-modulated radiation therapy were included. INTERVENTIONS: English-speaking patients completed European Organization for Research and Treatment of Cancer cancer-specific (C30) and site-specific (CR29) QOL questionnaires at baseline, at end of radiation, at 3 and 6 months, and then annually. MAIN OUTCOMES MEASURES: Long-term QOL was evaluated clinically (a change in score of ≥10 points was considered clinically significant) and statistically (using repeated-measurement analysis) by comparing the subscale scores at 1, 2, and 3 years with baseline scores. Subanalysis compared patients who received a radiation dose of 45 to 54 Gy versus 63 Gy. RESULTS: Ninety-six patients were included (median follow-up of 56.5 months). The symptom and functional scales showed a clinically significant decline at the end of treatment with improvement by 3 months after treatment. There was a long-term statistically significant decline in dyspnea, body image, bowel embarrassment, fecal incontinence, and hair loss, and there was long-term statistically and clinically significant worsening of impotence. Higher radiation dose (63 Gy) was not associated with significantly worse QOL. LIMITATIONS: Limitations included single-institution, single-arm study design, and lack of dose reconstruction (ie, analyses were based on prescribed, rather than delivered, dose). CONCLUSIONS: Patients with anal cancer treated with chemoradiation reported recovery of overall QOL to baseline levels. Specific symptoms remained bothersome, emphasizing the need to address and manage the chemoradiation-induced symptoms, during treatment and in the long term. See Video Abstract at http://links.lww.com/DCR/B905. IMPACTO DE LA QUIMIORRADIACIN DEFINITIVA EN CAMBIOS EN LA CALIDAD DE VIDA DE LOS PACIENTES CON CNCER ANAL RESULTADOS A LARGO PLAZO DE UN ESTUDIO PROSPECTIVE: ANTECEDENTES:Mantener y mejorar la calidad de vida son objetivos importantes del tratamiento del cáncer anal, ya que esta enfermedad generalmente es curable, con muchos sobrevivientes a largo plazo.OBJETIVO:Se evaluó la calidad de vida a largo plazo después de la quimiorradiación en pacientes con cáncer anal.DISEÑO:Este fue un estudio de cohorte prospectivo.ENTORNO CLINICO:Utilizamos datos de un estudio prospectivo en pacientes con cáncer anal tratados con quimiorradiación entre 2008-2013.PACIENTES:Los pacientes con cáncer anal fueron tratados con radioterapia de intensidad modulada guiada por imágenes.INTERVENCIONES:Los pacientes de habla inglesa completaron los cuestionarios de calidad de vida específicos de cáncer (C30) y específicos del sitio (CR29) de la Organización Europea para la Investigación y el Tratamiento del Cáncer al inicio, al final de la radiación, 3 y 6 meses, y luego anualmente.PRINCIPALES MEDIDAS DE RESULTADOS:Se evaluó a largo plazo la calidad de vida clínicamente (un cambio en la puntuación de ≥10 puntos se consideraron clínicamente significativo) y estadísticamente (usando análisis de medición repetida) comparando las subescalas de puntuación al 1, 2, y 3 años. Con puntuaciones de referencia. El subanálisis comparó pacientes que recibieron 45-54 Gy versus 63 Gy.RESULTADOS:Se incluyeron un total de 96 pacientes (mediana de seguimiento: 56,5 meses). La mayoría de las escalas funcionales y de síntomas mostraron una disminución clínicamente significativa al final del tratamiento con una mejoría a los 3 meses posteriores al tratamiento. Hubo una disminución estadísticamente significativa a largo plazo en disnea, imagen corporal, vergüenza intestinal, incontinencia fecal y pérdida de cabello; y hubo un empeoramiento a largo plazo estadística y clínicamente significativo en impotencia. La dosis de radiación más alta (63 Gy) no se asoció con una calidad de vida significativamente peor.LIMITACIONES:Institución única, diseño de estudio de un solo brazo y falta de recomposición de la dosis (es decir, los análisis se basan en la dosis prescrita, en lugar de la administrada).CONCLUSIÓNES:Los pacientes con cáncer anal tratados con quimiorradiación reportaron una recuperación de la QOL en general a los niveles de base. Síntomas específicos siguieron siendo molestos, lo que enfatiza la necesidad de resolver y tartar los síntomas inducidos por la quimiorradiación no solo durante el tratamiento, sino a largo plazo. Consulte Video Resumen en http://links.lww.com/DCR/B905. (Traducción- Dr. Francisco M. Abarca-Rendon).

Divergent clonal selection dominates medulloblastoma at recurrence.

The development of targeted anti-cancer therapies through the study of cancer genomes is intended to increase survival rates and decrease treatment-related toxicity. We treated a transposon-driven, functional genomic mouse model of medulloblastoma with 'humanized' in vivo therapy (microneurosurgical tumour resection followed by multi-fractionated, image-guided radiotherapy). Genetic events in recurrent murine medulloblastoma exhibit a very poor overlap with those in matched murine diagnostic samples (<5%). Whole-genome sequencing of 33 pairs of human diagnostic and post-therapy medulloblastomas demonstrated substantial genetic divergence of the dominant clone after therapy (<12% diagnostic events were retained at recurrence). In both mice and humans, the dominant clone at recurrence arose through clonal selection of a pre-existing minor clone present at diagnosis. Targeted therapy is unlikely to be effective in the absence of the target, therefore our results offer a simple, proximal, and remediable explanation for the failure of prior clinical trials of targeted therapy.

Simulated daily plan adaptation for magnetic resonance-guided liver stereotactic body radiotherapy.

INTRODUCTION: Liver cancers are challenging to treat using image-guided radiotherapy (IGRT) due to motion and deformation of target volumes and organs at risk (OARs), as well as difficulties in visualising liver tumours using cone-beam computed tomography (CBCT) based IGRT. Liver cancer patients may thus benefit from magnetic resonance (MR)-guided daily adaptive re-planning. We evaluated the dosimetric impact of a daily plan adaptation strategy based on daily MR imaging versus CBCT-based IGRT. METHODS: Ten patients were studied who were treated with CBCT-guided five-fraction stereotactic body radiotherapy (SBRT) and underwent MR imaging before each fraction. Simulated reference plans were created on computer tomography (CT) images and adapted plans were created on the daily MR images. Two plan adaptation strategies were retrospectively simulated: (1) translational couch shifts to match liver, mimicking standard CBCT guidance and (2) daily plan adaptation based on reference plan clinical goals and daily target and OAR contours. Dose statistics were calculated for both strategies and compared. RESULTS: Couch shifts resulted in an average reduction in GTV D99% relative to reference plan values of 5.2 Gy (-12.5% of reference values). Daily plan adaptation reduced this to 0.8 Gy (-2.0%). For six patients who were OAR dose-limited on reference plans, couch shifts resulted in OAR dose violations in 28 out of 28 simulated fractions, respectively; no violations occurred using daily plan adaptation. No OAR dose violations occurred using either strategy for the four cases not OAR dose-limited at reference planning. CONCLUSIONS: MR-guided daily plan adaptation ensured OAR dose constraints were met at all simulated treatment fractions while CBCT-based IGRT resulted in a systematic over-dosing of OARs in patients whose doses were limited by OAR dose at the time of reference planning.

Prospective evaluation of patient-reported anxiety and experiences with adaptive radiation therapy on an MR-linac.

Purpose: An integrated magnetic resonance scanner and linear accelerator (MR-linac) was implemented with daily online adaptive radiation therapy (ART). This study evaluated patient-reported experiences with their overall hospital care as well as treatment in the MR-linac environment. Methods: Patients pre-screened for MR eligibility and claustrophobia were referred to simulation on a 1.5 T MR-linac. Patient-reported experience measures were captured using two validated surveys. The 15-item MR-anxiety questionnaire (MR-AQ) was administered immediately after the first treatment to rate MR-related anxiety and relaxation. The 40-item satisfaction with cancer care questionnaire rating doctors, radiation therapists, the services and care organization and their outpatient experience was administered immediately after the last treatment using five-point Likert responses. Results were analyzed using descriptive statistics. Results: 205 patients were included in this analysis. Multiple sites were treated across the pelvis and abdomen with a median treatment time per fraction of 46 and 66 min respectively. Patients rated MR-related anxiety as "not at all" (87%), "somewhat" (11%), "moderately" (1%) and "very much so" (1%). Positive satisfaction responses ranged from 78 to 100% (median 93%) across all items. All radiation therapist-specific items were rated positively as 96-100%. The five lowest rated items (range 78-85%) were related to general provision of information, coordination, and communication. Overall hospital care was rated positively at 99%. Conclusion: In this large, single-institution prospective cohort, all patients had low MR-related anxiety and completed treatment as planned despite lengthy ART treatments with the MR-linac. Patients overall were highly satisfied with their cancer care involving ART using an MR-linac.

The Importance of Dosimetry Standardization in Radiobiology.

Radiation dose is central to much of radiobiological research. Precision and accuracy of dose measurements and reporting of the measurement details should be sufficient to allow the work to be interpreted and repeated and to allow valid comparisons to be made, both in the same laboratory and by other laboratories. Despite this, a careful reading of published manuscripts suggests that measurement and reporting of radiation dosimetry and setup for radiobiology research is frequently inadequate, thus undermining the reliability and reproducibility of the findings. To address these problems and propose a course of action, the National Cancer Institute (NCI), the National Institute of Allergy and Infectious Diseases (NIAID), and the National Institute of Standards and Technology (NIST) brought together representatives of the radiobiology and radiation physics communities in a workshop in September, 2011. The workshop participants arrived at a number of specific recommendations as enumerated in this paper and they expressed the desirability of creating dosimetry standard operating procedures (SOPs) for cell culture and for small and large animal experiments. It was also felt that these SOPs would be most useful if they are made widely available through mechanism(s) such as the web, where they can provide guidance to both radiobiologists and radiation physicists, be cited in publications, and be updated as the field and needs evolve. Other broad areas covered were the need for continuing education through tutorials at national conferences, and for journals to establish standards for reporting dosimetry. This workshop did not address issues of dosimetry for studies involving radiation focused at the sub-cellular level, internally-administered radionuclides, biodosimetry based on biological markers of radiation exposure, or dose reconstruction for epidemiological studies.

Evaluation of dosimetric predictors of toxicity after IMRT with concurrent chemotherapy for anal cancer.

BACKGROUND: This study investigates the impact of dosimetric parameters on acute and late toxicity for patients with anal squamous cell carcinoma (SCC) treated with image-guided intensity modulated radiation therapy (IG-IMRT) and concurrent chemotherapy. MATERIALS AND METHODS: Patients were enrolled in an observational cohort study between 2008 and 2013 (median follow-up 3.4 years). They were treated with standardized target and organ-at-risk (OAR) contouring, planning, and IG-IMRT. Radiotherapy dose, based on clinicopathologic features, ranged from 45 Gy to 63 Gy to gross targets and 27 Gy to 36 Gy to elective targets. Chemotherapy was concurrent 5-fluorouracil and mitomycin C (weeks 1&5). Toxicity was prospectively graded using NCI CTCAE v.3 and RTOG scales. Logistic regression was used to assess the association between dose/volume parameters (e.g small bowel V5) and corresponding grade 2 + and 3+ (G2+/3 + ) toxicities (e.g. diarrhea). RESULTS: In total, 87 and 79 patients were included in the acute and late toxicity analyses, respectively. The most common acute G2 + toxicities were skin (dermatitis in 87 % [inguino-genital skin], 91 % [perianal skin]) and hematologic in 58 %. G2 + late anal toxicity (sphincter dysfunction), gastrointestinal toxicity, and skin toxicity were respectively experienced by 49 %, 38 %, and 44 % of patients. Statistically significant associations were observed between: G2 + acute diarrhea and small bowel V35; G2 + acute genitourinary toxicity and bladder D0.5cc; G2 + inguino-genital skin toxicity and anterior skin V35; G2 + perianal skin toxicity and posterior skin V15; G2 + anemia and lower pelvis bone V45. D0.5 cc was significantly predictive of late toxicity (G2 + anal dysfunction, intestinal toxicity, and inguino-genital/perianal dermatitis). Maximum skin toxicity grade was significantly correlated with the requirement for a treatment break. CONCLUSION: Statistically significant dose-volume parameters were identified and may be used to offer individualized risk prediction and to inform treatment planning. Additional validation of the results is required.

Clinical Outcomes of Patients with Metastatic Breast Cancer Treated with Hypo-Fractionated Liver Radiotherapy.

PURPOSE: To retrospectively review the clinical outcomes of patients with metastatic breast cancer (MBCa) following liver directed ablative intent radiotherapy (RT). METHODS: Demographics, disease and treatment characteristics of patients with MBCa who received liver metastasis (LM) directed ablative RT between 2004-2020 were analysed. The primary outcome was local control (LC), secondary outcomes included overall survival (OS) and progression-free survival (PFS) analyzed by univariate (UVA) and multi-variable analysis (MVA). RESULTS: Thirty MBCa patients with 50 LM treated with 5-10 fraction RT were identified. Median follow-up was 14.6 (range 0.9-156.2) months. Class of metastatic disease was described as induced (12 patients, 40%), repeat (15 patients, 50%) and de novo (three patients, 10%). Median size of treated LM was 3.1 cm (range 1-8.8 cm) and median biologically effective dose delivered was 122 (Q1-Q3; 98-174) Gy3. One-year LC rate was 100%. One year and two-year survival was 89% and 63%, respectively, with size of treated LM predictive of OS (HR 1.35, p = 0.023) on UVA. Patients with induced OMD had a significantly higher rate of progression (HR 4.77, p = 0.01) on UVA, trending to significance on MVA (HR 3.23, p = 0.051). CONCLUSIONS: Hypo-fractionated ablative liver RT in patients with MBCa provides safe, tolerable treatment with excellent LC.

Practice-based training strategy for therapist-driven prostate MR-Linac adaptive radiotherapy.

Purpose: To develop a practice-based training strategy to transition from radiation oncologist to therapist-driven prostate MR-Linac adaptive radiotherapy. Methods and materials: In phase 1, 7 therapists independently contoured the prostate and organs-at-risk on T2-weighted MR images from 11 previously treated MR-Linac prostate patients. Contours were evaluated quantitatively (i.e. Dice similarity coefficient [DSC] calculated against oncologist generated online contours) and qualitatively (i.e. oncologist using a 5-point Likert scale; a score ≥ 4 was deemed a pass, a 90% pass rate was required to proceed to the next phase). Phase 2 consisted of supervised online workflow with therapists required no intervention from the oncologist on 10 total cases to advance. Phase 3 involved unsupervised therapist-driven workflow, with offline support from oncologists prior to the next fraction. Results: In phase 1, the mean DSC was 0.92 (range 0.85-0.97), and mean Likert score was 3.7 for the prostate. Five therapists did not attain a pass rate (3-5 cases with prostate contour score < 4), underwent follow-up one-on-one review, and performed contours on a further training set (n = 5). Each participant completed a median of 12 (range 10-13) cases in phase 2; of 82 cases, minor direction were required from the oncologist on 5 regarding target contouring. Radiation oncologists reviewed 179 treatment fractions in phase 3, and deemed 5 cases acceptable but with suggestions for next fraction; all other cases were accepted without suggestions. Conclusion: A training stepwise program was developed and successfully implemented to enable a therapist-driven workflow for online prostate MR-Linac adaptive radiotherapy.

Assessing the Accuracy of Bioluminescence Image-Guided Stereotactic Body Radiation Therapy of Orthotopic Pancreatic Tumors Using a Small Animal Irradiator.

Stereotactic body radiation therapy (SBRT) has shown promising results in the treatment of pancreatic cancer and other solid tumors. However, wide adoption of SBRT remains limited largely due to uncertainty about the treatment's optimal fractionation schedules to elicit maximal tumor response while limiting the dose to adjacent structures. A small animal irradiator in combination with a clinically relevant oncological animal model could address these questions. Accurate delivery of X rays to animal tumors may be hampered by suboptimal image-guided targeting of the X-ray beam in vivo. Integration of bioluminescence imaging (BLI) into small animal irradiators in addition to standard cone-beam computed tomography (CBCT) imaging improves target identification and high-precision therapy delivery to deep tumors with poor soft tissue contrast, such as pancreatic tumors. Using bioluminescent BxPC3 pancreatic adenocarcinoma human cells grown orthotopically in mice, we examined the performance of a small animal irradiator equipped with both CBCT and BLI in delivering targeted, hypo-fractionated, multi-beam SBRT. Its targeting accuracy was compared with magnetic resonance imaging (MRI)-guided targeting based on co-registration between CBCT and corresponding sequential magnetic resonance scans, which offer greater soft tissue contrast compared with CT alone. Evaluation of our platform's BLI-guided targeting accuracy was performed by quantifying in vivo changes in bioluminescence signal after treatment as well as staining of ex vivo tissues with γH2AX, Ki67, TUNEL, CD31 and CD11b to assess SBRT treatment effects. Using our platform, we found that BLI-guided SBRT enabled more accurate delivery of X rays to the tumor resulting in greater cancer cell DNA damage and proliferation inhibition compared with MRI-guided SBRT. Furthermore, BLI-guided SBRT allowed higher animal throughput and was more cost effective to use in the preclinical setting than MRI-guided SBRT. Taken together, our preclinical platform could be employed in translational research of SBRT of pancreatic cancer.

Patient-Reported and Clinical Outcomes From 5-Fraction SBRT for Oligometastases: A Prospective Single-Institution Study.

PURPOSE: To describe the long-term outcomes of a 5-fraction normal tissue tolerance adapted strategy for the management of oligometastases (OM). METHODS AND MATERIALS: Patients with histologically confirmed solid tumors, ≤5 extracranial metastases, suitable for a definitive approach for all metastatic lesions, at least one lesion suitable for Stereotactic Body Radiotherapy (SBRT), Eastern Coooperative Oncology Group Performance Status ≤2 were eligible. Treatment intervention was a 5-fraction (25-55 Gy) normal tissue adapted dosing strategy. The primary outcome was cumulative local progression rate at 12 months. RESULTS: Between March 2013 and January 2018, 137 patients started SBRT. Median follow-up was 35.7 months. In addition, 107 (78%) patients had a solitary OM. The mean planning target volume D95 was 39.6 (standard deviation, 8.8; biological effective dose using an alpha/beta ratio of 10, 70.8) Gy. Mean planning target volume D95 was highest for lung lesions (48.7 [standard deviation, 4.7]; biological effective dose using an alpha/beta ratio of 10, 96.1) Gy but was <40 Gy for all other anatomic sites. Two grade 3 toxicities (gastrointestinal bleed) were observed with stomach D0.05 30.3 Gy and 30.4 Gy. The cumulative local progression rate at 12 of 36 months was 16.1% (95% CI, 10-22) and 38.3% (95% CI 30-46.7); overall survival was 90% and 37%, and progression free survival was 58% and 19%, respectively. Mean symptom burden (Edmonton Symptom Assessment Total Score) worsened in patients with progressive disease (+8.8) at 12 months and was paralleled by changes in mean European Organization for Research and Treatment Quality of Life Core Questionnaire Summary Score and Global Health Quality of Life Score. Systemic therapy was initiated in 55% of patients at an average of 12.7 (standard deviation 12.4) months. CONCLUSIONS: If long-term progression free survival is the primary goal of therapy, SBRT for OM achieved this in <20% of patients attributable to a high risk of distant failure. Favorable local progression free survival is accompanied by preservation of quality of life, avoidance of symptom progression and reduced need of antineoplastic therapies at 12 months. Information on symptom burden, quality of life, as well as pattern of antineoplastic therapy use after progressive disease is useful to support conversations between patients, families, and health care providers. Strategies to improve patient selection and reduce distant progression rate remain a priority for further study.

The Impact of Disease Progression on Health-Related Quality of Life Outcomes in Patients With Oligometastatic Disease at 12 Months Post Stereotactic Body Radiation Therapy.

PURPOSE: There is a paucity of published health-related quality of life (HRQOL) outcomes in patients with oligometastatic disease (OMD) who receive stereotactic body radiation therapy (SBRT) and no available data assessing the effect of disease progression post-SBRT on HRQOL in this patient population. METHODS AND MATERIALS: Patients with OMD who received SBRT in a phase II single-arm research ethics board approved study were included. HRQOL was a secondary outcome. This study hypothesized that there is a different pattern of change from baseline HRQOL in patients with OMD treated with SBRT that have disease progression by 12 months (progressors) compared with those that do not progress by 12 months (nonprogressors), as measured by the European Organisation of Research and Treatment in Cancer Quality of Life Questionnaire Core 30. RESULTS: A total of 107 patients were included in this analysis, 41 without progression and 66 with progression by 12 months; median time to progression was 7.7 (0.3-57) months. A statistically significant decline in the mean global health/quality of life (GHQOL) score (73 [SD, 21.8] to 67.2 [SD, 27.1]; P = .04) from baseline in the entire population at the 12-month follow-up was found. Mean GHQOL change score in nonprogressors was -0.8 and in progressors was -8.8 (P = .07). However, only progressors demonstrated a difference between baseline and 12-month mean GHQOL scores (71.2 vs 62.4; P = .01), which was both statistically and clinically significant (-8.8) in the range of small minimal clinically important difference. There was a higher proportion of patients who experienced a minimal clinically important difference deterioration in progressors compared with nonprogressors (37.4% vs 24.4%; P = .14). CONCLUSIONS: Patients who progressed by 12 months did not have a statistical or clinically significant difference in mean GHQOL change score compared with nonprogressors. However, there were signals to suggest that patients who progressed by 12 months post-SBRT experienced a different pattern of change compared with nonprogressors, which was worse compared with baseline.

Heart irradiation as a risk factor for radiation pneumonitis.

PURPOSE: to investigate the potential role of incidental heart irradiation on the risk of radiation pneumonitis (RP) for patients receiving definitive radiation therapy for non-small-cell lung cancer (NSCLC). MATERIAL AND METHODS: two hundred and nine patient datasets were available for this study. Heart and lung dose-volume parameters were extracted for modeling, based on Monte Carlo-based heterogeneity corrected dose distributions. Clinical variables tested included age, gender, chemotherapy, pre-treatment weight-loss, performance status, and smoking history. The risk of RP was modeled using logistic regression. RESULTS: the most significant univariate variables were heart related, such as heart heart V65 (percent volume receiving at least 65 Gy) (Spearman Rs = 0.245, p < 0.001). The best-performing logistic regression model included heart D10 (minimum dose to the hottest 10% of the heart), lung D35, and maximum lung dose (Spearman Rs = 0.268, p < 0.0001). When classified by predicted risk, the RP incidence ratio between the most and least risky 1/3 of treatments was 4.8. The improvement in risk modeling using lung and heart variables was better than using lung variables alone. CONCLUSIONS: these results suggest a previously unsuspected role of heart irradiation in many cases of RP.

Implementation of Cardiac Stereotactic Radiotherapy: From Literature to the Linac.

Stereotactic radiotherapy (SBRT) has been applied to treat cardiac arrhythmias, but our institution had not yet implemented this technique. Here, we explain how we used implementation science and knowledge translation to provide cardiac SBRT to a critically ill patient with malignancy-associated refractory ventricular tachycardia. We reviewed the critical factors that enabled the implementation of this urgent treatment, such as the context of the implementation, the characteristics of the intervention, and the stakeholders. These principles can be used by other radiation programs to implement novel treatments in urgent settings, where the gold standard process of planning and developing policies and protocols is not possible.

Limited-stage small cell lung cancer: Outcomes associated with prophylactic cranial irradiation over a 20-year period at the Princess Margaret Cancer Centre.

BACKGROUND & PURPOSE: Prophylactic cranial irradiation (PCI) is recommended for limited-stage small-cell lung cancer (LS-SCLC) patients with good response to concurrent chemoradiation. We report our institution's 20-year experience with this patient population and associated clinical outcomes. MATERIALS & METHODS: A retrospective cohort of consecutive LS-SCLC patients treated with curative intent chemoradiation at our institution (1997-2018) was reviewed. Overall survival (OS) was calculated using the Kaplan-Meier method, and significant covariates determined by the Cox proportional hazards model. Covariates predictive of PCI were determined using Fisher's exact test and the Mann-Whitney test. Brain failure risk (BFR) was calculated using the cumulative incidence method treating death as a competing event. Treatment cohorts (historic vs. contemporary) were stratified by the median year of diagnosis (2005). RESULTS: A total of 369 patients with LS-SCLC were identified, of which 278 patients were notionally PCI eligible. PCI was given to 196 patients (71%). Younger age was associated with PCI utilization (p < 0.001). PCI utilization rates did not change between the historic and contemporary treatment era (p = 0.11), whereas magnetic resonance imaging (MRI) use at baseline and follow-up became more prevalent in the contemporary era (p = <0.001). On multivariable analysis, PCI utilization was associated with improved OS (HR 1.88, 95% CI 1.32-2.69) and decreased BFR (HR 4.66, 95% CI 2.58-8.40). Patients who had MRI follow-up had a higher incidence of BFR (HR 0.35, 95% CI 0.18-0.66) in multivariable analyses. CONCLUSIONS: For LS-SCLC patients at our institution, PCI is more frequently utilized in younger patients, and the utilization rate did not change significantly over the past 20 years. PCI was independently associated with improved OS and lower BFR. Omission of PCI in LS-SCLC patients should not be routinely practiced in the absence of further prospective data.

A Comparison of Hypofractionated and Twice-Daily Thoracic Irradiation in Limited-Stage Small-Cell Lung Cancer: An Overlap-Weighted Analysis.

Despite evidence for the superiority of twice-daily (BID) radiotherapy schedules, their utilization in practice remains logistically challenging. Hypofractionation (HFRT) is a commonly implemented alternative. We aim to compare the outcomes and toxicities in limited-stage small-cell lung cancer (LS-SCLC) patients treated with hypofractionated versus BID schedules. A bi-institutional retrospective cohort review was conducted of LS-SCLC patients treated with BID (45 Gy/30 fractions) or HFRT (40 Gy/15 fractions) schedules from 2007 to 2019. Overlap weighting using propensity scores was performed to balance observed covariates between the two radiotherapy schedule groups. Effect estimates of radiotherapy schedule on overall survival (OS), locoregional recurrence (LRR) risk, thoracic response, any ≥grade 3 (including lung, and esophageal) toxicity were determined using multivariable regression modelling. A total of 173 patients were included in the overlap-weighted analysis, with 110 patients having received BID treatment, and 63 treated by HFRT. The median follow-up was 20.4 months. Multivariable regression modelling did not reveal any significant differences in OS (hazard ratio [HR] 1.67, p = 0.38), LRR risk (HR 1.48, p = 0.38), thoracic response (odds ratio [OR] 0.23, p = 0.21), any ≥grade 3+ toxicity (OR 1.67, p = 0.33), ≥grade 3 pneumonitis (OR 1.14, p = 0.84), or ≥grade 3 esophagitis (OR 1.41, p = 0.62). HFRT, in comparison to BID radiotherapy schedules, does not appear to result in significantly different survival, locoregional control, or toxicity outcomes.

Investigation of energy dependence of EBT and EBT-2 gafchromic film.

PURPOSE: The purpose of this study was to quantify the extent of energy dependence of Gafchromic film to x-ray energies ranging in quality from 105 kVp to 6 MV, and relate this dependency to the film's chemical composition and date of production. METHODS: Lots of Gafchromic EBT film manufactured in 2004 and 2005 together with more recent batches produced in 2007 were evaluated for energy dependence. Multiple batches of EBT-2 film were also evaluated. Energy dependence was quantified as Rx-the ratio of net optical density (netOD) measured at a given energy x relative to the netOD measured at 6 MV, as measured on a linear accelerator. Rx was evaluated for beam qualities of 105 and 220 kVp on a clinical orthovoltage unit using two separate techniques-a flatbed scanner (Epson) and a real-time fiber-optic readout system. Neutron activation analysis for chlorine and bromine content was performed on all the films to determine whether the composition of the film had changed between batches of film exhibiting different energy dependence responses. RESULTS: For batches of EBT manufactured in 2007, R105 kVp was 0.75 and R220 kVp was 0.85, indicating an under-response at orthovoltage energies. These results were confirmed using both the Epson flatbed scanner as well as the real-time readout system. For batches of EBT film manufactured before 2006, Rl05 kVp ranged from 0.9 to 1.0. The results from the neutron activation analysis confirmed a direct relationship between the concentration of chlorine and the magnitude of under-response at orthovoltage energies. EBT-2 film exhibited R105 kVp values ranging from 0.79 (under-response) to 1.20 (over-response) among batches containing varying concentrations of bromine, chlorine, and potassium. CONCLUSIONS: The results of this study indicated that differences in energy response of EBT and EBT-2 films were due to differences in the chemical composition and therefore the effective atomic number of the film, which have changed over time. To achieve an energy independent dosimeter over a range of kilovoltage energies, the effective atomic number of the dosimeter must be closely matched to that of water. Small deviations in chemical composition can lead to large deviations in response as a function of energy.

Dosimetric variation due to the photon beam energy in the small-animal irradiation: a Monte Carlo study.

PURPOSE: The impact of photon beam energy and tissue heterogeneities on dose distributions and dosimetric characteristics such as point dose, mean dose, and maximum dose was investigated in the context of small-animal irradiation using Monte Carlo simulations based on the EGSnrc code. METHODS: Three Monte Carlo mouse phantoms, namely, heterogeneous, homogeneous, and bone homogeneous were generated based on the same mouse computed tomography image set. These phantoms were generated by overriding the tissue type of none of the voxels (heterogeneous), all voxels (homogeneous), and only the bone voxels (bone homogeneous) to that of soft tissue. Phase space files of the 100 and 225 kVp photon beams based on a small-animal irradiator (XRad225Cx, Precision X-Ray Inc., North Branford, CT) were generated using BEAMnrc. A 360 degrees photon arc was simulated and three-dimensional (3D) dose calculations were carried out using the DOSXYZnrc code through DOSCTP in the above three phantoms. For comparison, the 3D dose distributions, dose profiles, mean, maximum, and point doses at different locations such as the isocenter, lung, rib, and spine were determined in the three phantoms. RESULTS: The dose gradient resulting from the 225 kVp arc was found to be steeper than for the 100 kVp arc. The mean dose was found to be 1.29 and 1.14 times higher for the heterogeneous phantom when compared to the mean dose in the homogeneous phantom using the 100 and 225 kVp photon arcs, respectively. The bone doses (rib and spine) in the heterogeneous mouse phantom were about five (100 kVp) and three (225 kVp) times higher when compared to the homogeneous phantom. However, the lung dose did not vary significantly between the heterogeneous, homogeneous, and bone homogeneous phantom for the 225 kVp compared to the 100 kVp photon beams. CONCLUSIONS: A significant bone dose enhancement was found when the 100 and 225 kVp photon beams were used in small-animal irradiation. This dosimetric effect, due to the presence of the bone heterogeneity, was more significant than that due to the lung heterogeneity. Hence, for kV photon energies of the range used in small-animal irradiation, the increase of the mean and bone dose due to the photoelectric effect could be a dosimetric concern.

Datamining approaches for modeling tumor control probability.

BACKGROUND: Tumor control probability (TCP) to radiotherapy is determined by complex interactions between tumor biology, tumor microenvironment, radiation dosimetry, and patient-related variables. The complexity of these heterogeneous variable interactions constitutes a challenge for building predictive models for routine clinical practice. We describe a datamining framework that can unravel the higher order relationships among dosimetric dose-volume prognostic variables, interrogate various radiobiological processes, and generalize to unseen data before when applied prospectively. MATERIAL AND METHODS: Several datamining approaches are discussed that include dose-volume metrics, equivalent uniform dose, mechanistic Poisson model, and model building methods using statistical regression and machine learning techniques. Institutional datasets of non-small cell lung cancer (NSCLC) patients are used to demonstrate these methods. The performance of the different methods was evaluated using bivariate Spearman rank correlations (rs). Over-fitting was controlled via resampling methods. RESULTS: Using a dataset of 56 patients with primary NCSLC tumors and 23 candidate variables, we estimated GTV volume and V75 to be the best model parameters for predicting TCP using statistical resampling and a logistic model. Using these variables, the support vector machine (SVM) kernel method provided superior performance for TCP prediction with an rs=0.68 on leave-one-out testing compared to logistic regression (rs=0.4), Poisson-based TCP (rs=0.33), and cell kill equivalent uniform dose model (rs=0.17). CONCLUSIONS: The prediction of treatment response can be improved by utilizing datamining approaches, which are able to unravel important non-linear complex interactions among model variables and have the capacity to predict on unseen data for prospective clinical applications.

Quantifying Reoxygenation in Pancreatic Cancer During Stereotactic Body Radiotherapy.

Hypoxia, the state of low oxygenation that often arises in solid tumours due to their high metabolism and irregular vasculature, is a major contributor to the resistance of tumours to radiation therapy (RT) and other treatments. Conventional RT extends treatment over several weeks or more, and nominally allows time for oxygen levels to increase ("reoxygenation") as cancer cells are killed by RT, mitigating the impact of hypoxia. Recent advances in RT have led to an increase in the use stereotactic body radiotherapy (SBRT), which delivers high doses in five or fewer fractions. For cancers such as pancreatic adenocarcinoma for which hypoxia varies significantly between patients, SBRT might not be optimal, depending on the extent to which reoxygenation occurs during its short duration. We used fluoro-5-deoxy-α-D-arabinofuranosyl)-2-nitroimidazole positron-emission tomography (FAZA-PET) imaging to quantify hypoxia before and after 5-fraction SBRT delivered to patient-derived pancreatic cancer xenografts orthotopically implanted in mice. An imaging technique using only the pre-treatment FAZA-PET scan and repeat dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) scans throughout treatment was able to predict the change in hypoxia. Our results support the further testing of this technique for imaging of reoxygenation in the clinic.

A Mail Audit Independent Peer Review System for Dosimetry Verification of a Small Animal Irradiator.

Dedicated precision orthovoltage small animal irradiators have become widely available in the past decade and are commonly used for radiation biology research. However, there is a lack of dosimetric standardization among these irradiators, which affects the reproducibility of radiation-based animal studies. The purpose of this study was to develop a mail-based, independent peer review system to verify dose delivery among institutions using X-RAD 225Cx irradiators (Precision X-Ray, North Branford, CT). A robust, user-friendly mouse phantom was constructed from high-impact polystyrene and designed with dimensions similar to those of a typical laboratory mouse. The phantom accommodates three thermoluminescent dosimeters (TLDs) to measure dose. The mouse peer review system was commissioned in a small animal irradiator using anterior-posterior and posterior-anterior beams of 225 kVp and then mailed to three institutions to test the feasibility of the audit service. The energy correction factor for TLDs in the mouse phantom was derived to validate the delivered dose using this particular animal irradiation system. This feasibility study indicated that three institutions were able to deliver a radiation dose to the mouse phantom within ±10% of the target dose. The developed mail audit independent peer review system for the verification of mouse dosimetry can be expanded to characterize other commercially available orthovoltage irradiators, thereby enhancing the reproducibility of studies employing these irradiators.