Different benefits of adaptive radiotherapy for different histologies of NSCLC.

BACKGROUND: Adenocarcinoma (AC) and squamous cell carcinoma (SCC) are the most frequent histological subtypes of non-small cell lung cancer (NSCLC). The aim of this study was to investigate how patients with AC and SCC benefit from image-guided adaptive radiotherapy (ART) with tumour match. MATERIAL AND METHODS: Consecutive patients diagnosed with AC or SCC of the lung treated with definitive chemo-radiotherapy before and after the implementation of ART and tumour match were retrospectively included for analyses. Data collection included baseline patient and treatment characteristics in addition to clinical data on radiation pneumonitis (RP), failure, and survival. Patients were divided into four categories based on their histology and treatment before (n = 173 [89 AC and 84 SCC]) and after implementation of ART (n = 240 [141 AC and 99 SCC]). RESULTS: Median follow-up was 5.7 years for AC and 6.3 years for SCC. Mean lung dose decreased for both histologies with ART, whereas mean heart dose only decreased for patients with AC. Incidences of grade 3 and 5 RP decreased for both histologies with ART. Loco-regional failure (LRF) rates decreased significantly for patients with SCC after ART (p = .04), no significant difference was observed for AC. Overall survival (OS) increased significantly for SCC after ART (p < .01): the 2-year OS increased from 31.0% (95% confidence interval [CI] [22.5-42.6]) to 54.5% (95% CI [45.6-65.3]). No significant effect on OS was observed for patients with AC. CONCLUSION: ART and tumour match in the radiotherapeutic treatment of patients with locally advanced NSCLC primarily led to decreased LRF and improved OS for patients with SCC.

European Society for Radiotherapy and Oncology and European Organisation for Research and Treatment of Cancer consensus on re-irradiation: definition, reporting, and clinical decision making.

Re-irradiation can be considered for local recurrence or new tumours adjacent to a previously irradiated site to achieve durable local control for patients with cancer who have otherwise few therapeutic options. With the use of new radiotherapy techniques, which allow for conformal treatment plans, image guidance, and short fractionation schemes, the use of re-irradiation for different sites is increasing in clinical settings. Yet, prospective evidence on re-irradiation is scarce and our understanding of the underlying radiobiology is poor. Our consensus on re-irradiation aims to assist in re-irradiation decision making, and to standardise the classification of different forms of re-irradiation and reporting. The consensus has been endorsed by the European Society for Radiotherapy and Oncology and the European Organisation for Research and Treatment of Cancer. The use of this classification in daily clinical practice and research will facilitate accurate understanding of the clinical implications of re-irradiation and allow for cross-study comparisons. Data gathered in a uniform manner could be used in the future to make recommendations for re-irradiation on the basis of clinical evidence. The consensus document is based on an adapted Delphi process and a systematic review of the literature was done according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).

Prognostic factors for patients with anal cancer treated with conformal radiotherapy-a systematic review.

AIMS: Anal cancer is primarily treated using concurrent chemoradiotherapy (CRT), with conformal techniques such as intensity modulated radiotherapy (IMRT) and volumetric arc therapy (VMAT) now being the standard techniques utilised across the world. Despite this, there is still very limited consensus on prognostic factors for outcome following conformal CRT. This systematic review aims to evaluate the existing literature to identify prognostic factors for a variety of oncological outcomes in anal cancer, focusing on patients treated with curative intent using contemporary conformal radiotherapy techniques. MATERIALS AND METHODS: A literature search was conducted using Medline and Embase to identify studies reporting on prognostic factors for survival and cancer-related outcomes after conformal CRT for anal cancer. The prognostic factors which were identified as significant in univariable and multivariable analysis, along with their respective factor effects (where available) were extracted. Only factors reported as prognostic in more than one study were included in the final results. RESULTS: The results from 19 studies were analysed. In both univariable and multivariable analysis, N stage, T stage, and sex were found to be the most prevalent and reliable clinical prognostic factors for the majority of outcomes explored. Only a few biomarkers have been identified as prognostic by more than one study - pre-treatment biopsy HPV load, as well as the presence of leukocytosis, neutrophilia and anaemia at baseline measurement. The results also highlight the lack of studies with large cohorts exploring the prognostic significance of imaging factors. CONCLUSION: Establishing a set of prognostic and potentially predictive factors for anal cancer outcomes can guide the risk stratification of patients, aiding the design of future clinical trials. Such trials will in turn provide us with greater insight into how to effectively treat this disease using a more personalised approach.

Dose summation and image registration strategies for radiobiologically and anatomically corrected dose accumulation in pelvic re-irradiation.

BACKGROUND: Re-irradiation (reRT) is a promising technique for patients with localized recurrence in a previously irradiated area but presents major challenges. These include how to deal with anatomical change between two courses of radiotherapy and integration of radiobiology when summating original and re-irradiation doses. The Support Tool for Re-Irradiation Decisions guided by Radiobiology (STRIDeR) project aims to develop a software tool for use in a commercial treatment planning system to facilitate more informed reRT by accounting for anatomical changes and incorporating radiobiology. We evaluated three approaches to dose summation, incorporating anatomical change and radiobiology to differing extents. METHODS: In a cohort of 21 patients who previously received pelvic re-irradiation the following dose summation strategies were compared: (1) Rigid registration (RIR) and physical dose summation, to reflect the current clinical approach, (2) RIR and radiobiological dose summation in equivalent dose in 2 Gy fractions (EQD2), and (3) Patient-specific deformable image registration (DIR) with EQD2 dose summation. RESULTS: RIR and physical dose summation (Strategy 1) resulted in high cumulative organ at risk (OAR) doses being 'missed' in 14% of cases, which were highlighted by EQD2 dose summation (Strategy 2). DIR (with EQD2 dose summation; Strategy 3) resulted in improved OAR overlap and distance to agreement metrics compared to RIR (with EQD2 dose summation; Strategy 2) and was consistently preferred in terms of clinical utility. DIR was considered to have a clinically important impact on dose summation in 38% of cases. CONCLUSION: Re-irradiation cases require individualized assessment when considering dose summation with the previous treatment plan. Fractionation correction is necessary to meaningfully assess cumulative doses and reduce the risk of unintentional OAR overdose. DIR can add clinically relevant information in selected cases, especially for significant anatomical change. Robust solutions for cumulative dose assessment offer the potential for future improved understanding of cumulative OAR tolerances.

Dose-Response and Normal Tissue Complication Probabilities after Proton Therapy for Choroidal Melanoma.

PURPOSE: Normal tissue complication probability (NTCP) models could aid the understanding of dose dependence of radiation-induced toxicities after eye-preserving radiotherapy of choroidal melanomas. We performed NTCP-modeling and established dose-response relationships for visual acuity (VA) deterioration and common late complications after treatments with proton therapy (PT). DESIGN: Retrospective study from single, large referral center. PARTICIPANTS: We considered patients from Nice, France, diagnosed with choroidal melanoma and treated primarily with hypofractionated PT (52 Gy physical dose in 4 fractions). Complete VA deterioration information was available for 1020 patients, and complete information on late complications was available for 991 patients. METHODS: Treatment details, dose-volume histograms (DVHs) for relevant anatomic structures, and patient and tumor characteristics were available from a dedicated ocular database. Least absolute shrinkage and selection operator (LASSO) variable selection was used to identify variables with the strongest impact on each end point, followed by multivariate Cox regressions and logistic regressions to analyze the relationships among dose, clinical characteristics, and clinical outcomes. MAIN OUTCOME MEASURES: Dose-response relationship for VA deterioration and late complications. RESULTS: Dose metrics for several structures (i.e., optic disc, macula, retina, globe, lens, ciliary body) correlated with clinical outcome. The near-maximum dose to the macula showed the strongest correlation with VA deterioration. The near-maximum dose to the retina was the only variable with clear impact on the risk of maculopathy, the dose to 20% of the optic disc had the largest impact on optic neuropathy, dose to 20% of cornea had the largest impact on neovascular glaucoma, and dose to 20% of the ciliary body had the largest impact on ocular hypertension. The volume of the ciliary body receiving 26 Gy was the only variable associated with the risk of cataract, and the volume of retina receiving 52 Gy was associated with the risk of retinal detachment. Optic disc-to-tumor distance was the only variable associated with dry eye syndrome in the absence of DVH for the lachrymal gland. CONCLUSIONS: VA deterioration and specific late complications demonstrated dependence on dose delivered to normal structures in the eye after PT for choroidal melanoma. VA deterioration depended on dose to a range of structures, whereas more specific complications were related to dose metrics for specific structures.

Tumour control probability after Ruthenium-106 brachytherapy for choroidal melanomas.

Purpose: Ruthenium-106 (Ru-106) brachytherapy is a common eye-preserving treatment for choroidal melanomas. However, a dose-response model describing the relationship between the actual delivered tumour dose and tumour control has, to the best of our knowledge, not previously been quantified for Ru-106 brachytherapy; we aimed to rectify this.Material and methods: We considered consecutive patients with primary choroidal melanomas, treated with Ru-106 brachytherapy (2005-2014). Dosimetric plans were retrospectively recreated using 3D image-guided planning software. Pre-treatment fundus photographies were used to contour the tumour; post-treatment photographies to determine the accurate plaque position. Patient and tumour characteristics, treatment details, dose volume histograms, and clinical outcomes were extracted. Median follow-up was 5.0 years. The relationship between tumour dose and risk of local recurrence was examined using multivariate Cox regression modelling, with minimum physical tumour dose (D99%) as primary dose metric.Results: We included 227 patients with median tumour height and largest base dimension of 4 mm (range 1-12, IQR 3-6) and 11 mm (range 4-23, IQR 9-13). The estimated 3 year local control was 82% (95% CI 77-88). Median D99% was 105 Gy (range 6-783, IQR 65-138); this was the most significant factor associated with recurrence (p < .0001), although tumour height, combined TTT and Ru-106 brachytherapy, and sex were also significant. The hazard ratio (HR) for a 10 Gy increase in D99% was 0.87 (95% CI 0.82-0.93). Using biological effective dose in the model resulted in no substantial difference in dose dependence estimates. Robustness cheques with D1-99% showed D99% to be the most significant dose metric for local recurrence.Conclusion: The minimum tumour dose correlated strongly with risk of tumour recurrence, with 100 Gy needed to ensure at least 84% local control at 3 years.

Feasibility of preference-driven radiotherapy dose treatment planning to support shared decision making in anal cancer.

PURPOSE/OBJECTIVE: Chemo-radiotherapy is an established primary curative treatment for anal cancer, but clinically equal rationale for different target doses exists. If joint preferences (physician and patient) are used to determine acceptable tradeoffs in radiotherapy treatment planning, multiple dose plans must be simultaneously explored. We quantified the degree to which different toxicity priorities might be incorporated into treatment plan selection, to elucidate the feasible decision space for shared decision making in anal cancer radiotherapy. MATERIAL AND METHODS: Retrospective plans were generated for 22 anal cancer patients. Multi-criteria optimization handles dynamically changing priorities between clinical objectives while meeting fixed clinical constraints. Four unique dose distributions were designed to represent a wide span of clinically relevant objectives: high-dose preference (60.2 Gy tumor boost and 50.4 Gy to elective nodes with physician-defined order of priorities), low-dose preference (53.75 Gy tumor boost, 45 Gy to elective nodes, physician-defined priorities), bowel sparing preference (lower dose levels and priority for bowel avoidance) and bladder sparing preference (lower dose levels and priority for bladder avoidance). RESULTS: Plans satisfied constraints for target coverage. A senior oncologist approved a random subset of plans for quality assurance. Compared to a high-dose preference, bowel sparing was clinically meaningful at the lower prescribed dose [median change in V45Gy: 234 cm3; inter-quartile range (66; 247); p < .01] and for a bowel sparing preference [median change in V45Gy: 281 cm3; (73; 488); p < .01]. Compared to a high-dose preference, bladder sparing was clinically meaningful at the lower prescribed dose [median change in V35Gy: 13.7%-points; (0.3; 30.6); p < .01] and for a bladder sparing preference [median change in V35Gy: 30.3%-points; (12.4; 43.1); p < .01]. CONCLUSIONS: There is decision space available in anal cancer radiotherapy to incorporate preferences, although tradeoffs are highly patient-dependent. This study demonstrates that preference-informed dose planning is feasible for clinical studies utilizing shared decision making.

Technological advances in radiotherapy of rectal cancer: opportunities and challenges.

PURPOSE OF REVIEW: This review summarizes the available evidence for the use of modern radiotherapy techniques for chemoradiotherapy for rectal cancer, with specific focus on intensity-modulated radiotherapy (IMRT) and volumetric arc therapy (VMAT) techniques. RECENT FINDINGS: The dosimetric benefits of IMRT and VMAT are well established, but prospective clinical studies are limited, with phase I-II studies only. Recent years have seen the publication of a few larger prospective patient series as well as some retrospective cohorts, several of which include much needed late toxicity data. Overall results are encouraging, as toxicity levels - although varying across reports - appear lower than for 3D conformal radiotherapy. Innovative treatment techniques and strategies which may be facilitated by the use of IMRT/VMAT include simultaneously integrated tumour boost, adaptive treatment, selective sparing of specific organs to enable chemotherapy escalation, and nonsurgical management. SUMMARY: Few prospective studies of IMRT and VMAT exist, which causes uncertainty not just in regards to the clinical benefit of these technologies but also in the optimal use. The priority for future research should be subgroups of patients who might receive relatively greater benefit from innovative treatment techniques, such as patients receiving chemoradiotherapy with definitive intent and patients treated with dose escalation.

High-dose chemoradiotherapy and watchful waiting for distal rectal cancer: a prospective observational study.

BACKGROUND: Abdominoperineal resection is the standard treatment for patients with distal T2 or T3 rectal cancers; however, the procedure is extensive and mutilating, and alternative treatment strategies are being investigated. We did a prospective observational trial to assess whether high-dose radiotherapy with concomitant chemotherapy followed by observation (watchful waiting) was successful for non-surgical management of low rectal cancer. METHODS: Patients with primary, resectable, T2 or T3, N0-N1 adenocarcinoma in the lower 6 cm of the rectum were given chemoradiotherapy (60 Gy in 30 fractions to tumour, 50 Gy in 30 fractions to elective lymph node volumes, 5 Gy endorectal brachytherapy boost, and oral tegafur-uracil 300 mg/m(2)) every weekday for 6 weeks. Endoscopies and biopsies of the tumour were done at baseline, throughout the course of treatment (weeks 2, 4, and 6), and 6 weeks after the end of treatment. We allocated patients with complete clinical tumour regression, negative tumour site biopsies, and no nodal or distant metastases on CT and MRI 6 weeks after treatment to the observation group (watchful waiting). We referred all other patients to standard surgery. Patients under observation were followed up closely with endoscopies and selected-site biopsies, with surgical resection given for local recurrence. The primary endpoint was local tumour recurrence 1 year after allocation to the observation group. This study is registered with ClinicalTrials.gov, number NCT00952926. Enrolment is closed, but follow-up continues for secondary endpoints. FINDINGS: Between Oct 20, 2009, and Dec 23, 2013, we enrolled 55 patients. Patients were recruited from three surgical units throughout Denmark and treated in one tertiary cancer centre (Vejle Hospital, Vejle, Denmark). Of 51 patients who were eligible, 40 had clinical complete response and were allocated to observation. Median follow-up for local recurrence in the observation group was 23·9 months (IQR 15·3-31·0). Local recurrence in the observation group at 1 year was 15·5% (95% CI 3·3-26·3). The most common acute grade 3 adverse event during treatment was diarrhoea, which affected four (8%) of 51 patients. Sphincter function in the observation group was excellent, with 18 (72%) of 25 patients at 1 year and 11 (69%) of 16 patients at 2 years reporting no faecal incontinence at all and a median Jorge-Wexner score of 0 (IQR 0-0) at all timepoints. The most common late toxicity was bleeding from the rectal mucosa; grade 3 bleeding was reported in two (7%) in 30 patients at 1 year and one (6%) of 17 patients at 2 years. There were no unexpected serious adverse reactions or treatment-related deaths. INTERPRETATION: High-dose chemoradiotherapy and watchful waiting might be a safe alternative to abdominoperineal resection for patients with distal rectal cancer. FUNDING: CIRRO-The Lundbeck Foundation Center for Interventional Research in Radiation Oncology and The Danish Council for Strategic Research.

Dose-response of acute urinary toxicity of long-course preoperative chemoradiotherapy for rectal cancer.

BACKGROUND: Long-course preoperative chemoradiotherapy (chemo-RT) improves outcomes for rectal cancer patients, but acute side effects during treatment may cause considerable patient discomfort and may compromise treatment compliance. We developed a dose-response model for acute urinary toxicity based on a large, single-institution series. MATERIAL AND METHODS: In total 345 patients were treated with (chemo-)RT for primary rectal cancer from January 2007 to May 2012. Urinary toxicity during RT was scored prospectively using the CTCAE v 3.0 cystitis score (grade 0-5). Clinical variables and radiation dose to the bladder were related to graded toxicity using multivariate ordinal logistic regression. Three models were optimized, each containing all available clinical variables and one of three dose metrics: Mean dose (Dmean), equivalent uniform dose (EUD), or relative volume given x Gy or above (dose cut-off model, Vx). The optimal dose metric was chosen using the Akaike Information Criterion (AIC). RESULTS: Grade 1 cystitis was experienced by 138 (40%), grade 2 by 39 (11%) and grade 3 by two (1%) patients, respectively. Dose metrics were significantly correlated with toxicity in all models, but the dose cut-off model provided the best AIC value. The only significant clinical risk factors in the Vx model were male gender (p = 0.006) and brachytherapy boost (p = 0.02). Reducing the model to include gender, brachytherapy boost and Vx yielded odds ratios ORmale = 1.82 (1.17-2.80), ORbrachy = 1.36 (1.02-1.80 for each 5 Gy), x = 35.1 Gy (28.6-41.5 Gy). The predicted risk of grade 2 and above cystitis ranged from 2% to 26%. CONCLUSION: Acute cystitis correlated significantly with radiation dose to the bladder; the dose-cut-off model (V35Gy) was superior to Dmean and EUD models. Male gender and brachytherapy boost increased the risk of toxicity. Wide variation in predicted risks suggests room for treatment optimization using individual dose constraints.

Cell-free DNA in healthy individuals, noncancerous disease and strong prognostic value in colorectal cancer.

The purpose was to investigate total cell-free DNA (cfDNA) in colorectal cancer (CRC) patients during treatment with second-line chemotherapy and in healthy controls and patients with different comorbidities. Patient treated with second-line irinotecan for metastatic CRC (n = 100), a cohort of healthy controls with and without comorbidity (n = 70 and 100, respectively) were included. cfDNA was quantified by an in-house developed quantitative polymerase chain reaction from plasma samples drawn prior to the first cycle of chemotherapy and at time of progression. cfDNA levels were significantly higher in CRC compared to controls, with a clear capability for discriminating between the groups (receiver operation curve analysis; area under the curve 0.82, p < 0.0001). Patients with high levels had a shorter survival from irinotecan compared to those with lover levels. The cohort independent upper normal limit divided patients into high and low risk groups. The progression-free survival (PFS) was 2.1 months [95% confidence interval (CI) 2.0-3.4] and 6.5 (95% CI 4.2-7.2) months [hazard ratio (HR) 2.53; 95% CI 1.57-4.06, p < 0.0001] and overall survival (OS) 7.4 months (95% CI 4.3-8.7) and 13.8 months (95% CI 11.9-18.9; HR 2.52; 95% CI 1.54-4.13, p < 0.0000), respectively. Cox regression multivariate analysis showed a PFS HR of 1.4 (95% CI 1.1-1.7) for each increase in cfDNA quartile, p = 0.03 and 1.6 (1.3-2.0) for OS, p < 0.0001, respectively. A combined marker analysis with plasma KRAS mutations added further prognostic impact, which was consistent when performed on the samples drawn at time of progression. In conclusion, cfDNA measurement holds important clinical information and could become a useful tool for prediction of outcome from chemotherapy in mCRC.

Towards individualized dose constraints: Adjusting the QUANTEC radiation pneumonitis model for clinical risk factors.

BACKGROUND: Understanding the dose-response of the lung in order to minimize the risk of radiation pneumonitis (RP) is critical for optimization of lung cancer radiotherapy. We propose a method to combine the dose-response relationship for RP in the landmark QUANTEC paper with known clinical risk factors, in order to enable individual risk prediction. The approach is validated in an independent dataset. MATERIAL AND METHODS: The prevalence of risk factors in the patient populations underlying the QUANTEC analysis was estimated, and a previously published method to adjust dose-response relationships for clinical risk factors was employed. Effect size estimates (odds ratios) for risk factors were drawn from a recently published meta-analysis. Baseline values for D50 and γ50 were found. The method was tested in an independent dataset (103 patients), comparing the predictive power of the dose-only QUANTEC model and the model including risk factors. Subdistribution cumulative incidence functions were compared for patients with high/low-risk predictions from the two models, and concordance indices (c-indices) for the prediction of RP were calculated. RESULTS: The reference dose- response relationship for a patient without pulmonary co-morbidities, caudally located tumor, no history of smoking, < 63 years old, and receiving no sequential chemotherapy was estimated as D50(0) = 34.4 Gy (95% CI 30.7, 38.9), γ50(0) = 1.19 (95% CI 1.00, 1.43). Individual patient risk estimates were calculated. The cumulative incidences of RP in the validation dataset were not significantly different in high/low-risk patients when doing risk allocation with the QUANTEC model (p = 0.11), but were significantly different using the individualized model (p = 0.006). C-indices were significantly different between the dose-only and the individualized model. CONCLUSION: This study presents a method to combine a published dose-response function with known clinical risk factors and demonstrates the increased predictive power of the combined model. The method allows for individualization of dose constraints and individual patient risk estimates.

Individual lymph node position variation for rectal cancer patients treated with long course chemoradiotherapy.

Background and purpose: Delivery of high precision radiotherapy lymph node boosts requires detailed information on the interfraction positional variation of individual lymph nodes. In this study we characterized interfraction positional shifts of suspected malignant lymph nodes for rectal cancer patients receiving long course radiotherapy. Furthermore, we investigated parameters which could affect the magnitude of the position variation. Materials and Methods: Fourteen patients from a prospective clinical imaging study with a total of 61 suspected malignant lymph nodes in the mesorectum, presacral, and lateral regions, were included. The primary gross tumor volume (GTVp) and all suspected malignant lymph nodes were delineated on six magnetic resonance imaging scans per patient. Positional variation was calculated as systematic and random errors, based on shifts of center-of-mass, and estimated relative to either bony structures or the GTVp using a hierarchical linear mixed model. Results: Depending on location and direction, systematic and random variations (relative to bony structures) were within 0.6-2.8 mm and 0.6-2.9 mm, respectively. Systematic and random variations increased when evaluating position relative to GTVp (median increase of 0.6 mm and 0.5 mm, respectively). Correlations with scan time-point and relative bladder volume were found in some directions. Conclusions: Using linear mixed modeling, we estimated systematic and random positional variation for suspected malignant lymph nodes in rectal cancer patients treated with long course radiotherapy. Statistically significant correlations of the magnitude of the lymph node shifts were found related to scan time-point and relative bladder volume.

Early radiologic and metabolic tumour response assessment during combined chemo-radiotherapy for locally advanced NSCLC.

Background: The role of early treatment response for patients with locally advanced non-small cell lung cancer (LA-NSCLC) treated with concurrent chemo-radiotherapy (cCRT) is unclear. The study aims to investigate the predictive value of response to induction chemotherapy (iCX) and the correlation with pattern of failure (PoF). Materials and methods: Patients with LA-NSCLC treated with cCRT were included for analyses (n = 276). Target delineations were registered from radiotherapy planning PET/CT to diagnostic PET/CT, in between which patients received iCX. Volume, sphericity, and SUVpeak were extracted from each scan. First site of failure was categorised as loco-regional (LR), distant (DM), or simultaneous LR+M (LR+M). Fine and Gray models for PoF were performed: a baseline model (including performance status (PS), stage, and histology), an image model for squamous cell carcinoma (SCC), and an image model for non-SCC. Parameters included PS, volume (VOL) of tumour, VOL of lymph nodes, ΔVOL, sphericity, SUVpeak, ΔSUVpeak, and oligometastatic disease. Results: Median follow-up was 7.6 years. SCC had higher sub-distribution hazard ratio (sHR) for LRF (sHR = 2.771 [1.577:4.87], p < 0.01) and decreased sHR for DM (sHR = 0.247 [0.125:0.485], p  <  0.01). For both image models, high diagnostic SUVpeak increased risk of LRF (sHR = 1.059 [1.05:1.106], p < 0.01 for SCC, sHR = 1.12 [1.03:1.21], p < 0.01 for non-SCC). Patients with SCC and less decrease in VOL had higher sHR for DM (sHR = 1.025[1.001:1.048] pr. % increase, p = 0.038). Conclusion: Poor response in disease volume was correlated with higher sHR of DM for SCC, no other clear correlation of response and PoF was observed. Histology significantly correlated with PoF with SCC prone to LRF and non-SCC prone to DM as first site of failure. High SUVpeak at diagnosis increased the risk of LRF for both histologies.

Treatment planning for patients with low rectal cancer in a multicenter prospective organ preservation study.

BACKGROUND: Non-surgical management of rectal cancer relies on (chemo)radiotherapy as the definitive treatment modality. This study reports and evaluates the clinical high dose radiotherapy treatment plans delivered to patients with low resectable rectal cancer in a Danish multicenter trial. METHODS: The Danish prospective multicenter phase II Watchful Waiting 2 trial (NCT02438839) investigated definitive chemoradiation for non-surgical management of low rectal cancer. Three Danish centers participated in the trial and committed to protocol-specified treatment planning and delivery requirements. The protocol specified a dose of 50.4 Gy in 28 fractions to the elective volume (CTV-/PTV-E) and a concomitant boost of 62 Gy in 28 fractions to the primary target volume (CTV-/PTV-T). RESULTS: The trial included 108 patients, of which 106 treatment plans were available for retrospective analysis. Dose coverage planning goals for the main target structures were fulfilled for 94% of the treatment plans. However, large intercenter differences in doses to organs-at-risk (OARs) were seen, especially for the intestines. Five patients had a V60Gy>10 cm3 for the intestines and two patients for the bladder. CONCLUSION: Prescribed planning goals for target coverage were fulfilled for 94% of the treatment plans, however analysis of OAR doses and volumes indicated intercenter variations. Dose escalation to 62 Gy (as a concomitant boost to the primary tumor) introduced no substantial high dose volumes (>60 Gy) to the bladder and intestines. The treatment planning goals may be used for future prospective evaluation of highdose radiotherapy for organ preservation for low rectal cancer.

Reirradiation - still navigating uncharted waters?

With the emergence of high-precision radiotherapy technologies such as stereotactic ablative radiotherapy (SABR), MR guided brachytherapy, image guided intensity modulated photon and proton radiotherapy and most recently daily adaptive radiotherapy, reirradiation is increasingly recognized as a viable treatment option for many patients. This includes those with recurrent, metastatic or new malignancies post initial radiotherapy. The primary challenge in reirradiation lies in balancing tumor control against the risk of severe toxicity from cumulative radiation doses to previously irradiated normal tissue. Although technology for precise delivery has advanced at a fast pace, clinical practice of reirradiation still mostly relies on individual expertise, as prospective evidence is scarce, the level of reporting in clinical studies is not standardized and of low quality - especially with respect to cumulative doses received by organs at risk. A recent ESTRO/EORTC initiative proposed a standardized definition of reirradiation and formulated general requirements for minimal reporting in clinical studies [1]. As a consequence we found it timely to convene for an international and interdisciplinary meeting with experts in the field to summarize the current evidence, identify knowledge gaps and explore which best practices can be derived for safe reirradiation. The meeting was held on 15.06.2023 in Zurich and was endorsed by the scientific societies SASRO, DEGRO and ESTRO. Here, we report on available evidence and research priorities in the field of reirradiation, as discussed during the meeting.

Multi-centre evaluation of variation in cumulative dose assessment in reirradiation scenarios.

BACKGROUND AND PURPOSE: Safe reirradiation relies on assessment of cumulative doses to organs at risk (OARs) across multiple treatments. Different clinical pathways can result in inconsistent estimates. Here, we quantified the consistency of cumulative dose to OARs across multi-centre clinical pathways. MATERIAL AND METHODS: We provided DICOM planning CT, structures and doses for two reirradiation cases: head & neck (HN) and lung. Participants followed their standard pathway to assess the cumulative physical and EQD2 doses (with provided α/ß values), and submitted DVH metrics and a description of their pathways. Participants could also submit physical dose distributions from Course 1 mapped onto the CT of Course 2 using their best available tools. To assess isolated impact of image registrations, a single observer accumulated each submitted spatially mapped physical dose for every participating centre. RESULTS: Cumulative dose assessment was performed by 24 participants. Pathways included rigid (n = 15), or deformable (n = 5) image registration-based 3D dose summation, visual inspection of isodose line contours (n = 1), or summation of dose metrics extracted from each course (n = 3). Largest variations were observed in near-maximum cumulative doses (25.4 - 41.8 Gy for HN, 2.4 - 33.8 Gy for lung OARs), with lower variations in volume/dose metrics to large organs. A standardised process involving spatial mapping of the first course dose to the second course CT followed by summation improved consistency for most near-maximum dose metrics in both cases. CONCLUSION: Large variations highlight the uncertainty in reporting cumulative doses in reirradiation scenarios, with implications for outcome analysis and understanding of published doses. Using a standardised workflow potentially including spatially mapped doses improves consistency in determination of accumulated dose in reirradiation scenarios.

Re-irradiation in clinical practice: Results of an international patterns of care survey within the framework of the ESTRO-EORTC E2-RADIatE platform.

BACKGROUND: Re-irradiation is an increasingly utilized treatment for recurrent, metastatic or new malignancies after previous radiotherapy. It is unclear how re-irradiation is applied in clinical practice. We aimed to investigate the patterns of care of re-irradiation internationally. MATERIAL/METHODS: A cross-sectional survey conducted between March and September 2022. The survey was structured into six sections, each corresponding to a specific anatomical region. Participants were instructed to complete the sections of their clinical expertise. A total of 15 multiple-choice questions were included in each section, addressing various aspects of the re-irradiation process. The online survey targeted radiation and clinical oncologists and was endorsed by the European Society for Radiotherapy and Oncology (ESTRO) and the European Organisation for Research and Treatment of Cancer (EORTC). RESULTS: 371 physicians from 55 countries across six continents participated. Participants had a median professional experience of 16 years, and the majority (60%) were affiliated with an academic hospital. The brain region was the most common site for re-irradiation (77%), followed by the pelvis (65%) and head and neck (63%). Prolonging local control was the most common goal (90-96% across anatomical regions). The most common minimum interval between previous radiotherapy and re-irradiation was 6-12 months (45-55%). Persistent grade 3 or greater radiation-induced toxicity (77-80%) was the leading contraindication. Variability in organs at risk dose constraints for re-irradiation was observed. Advanced imaging modalities and conformal radiotherapy techniques were predominantly used. A scarcity of institutional guidelines for re-irradiation was reported (16-19%). Participants from European centers more frequently applied thoracic and abdominal re-irradiation. Indications did not differ between academic and non-academic hospitals. CONCLUSION: This study highlights the heterogeneity in re-irradiation practices across anatomical regions and emphasizes the need for high-quality evidence from prospective studies to guide treatment decisions and derive safe cumulative dose constraints.

Endorectal contact radiation boosting: Making the case for dose AND volume reporting.

INTRODUCTION: The various rectal endoluminal radiation techniques all have steep, but different, dose gradients. In rectal contact brachytherapy (CXB) doses are typically prescribed and reported to the applicator surface and not to the gross tumor volume (GTV), clinical target volume (CTV) or organs at risk (OAR), which is crucial to understand tumor response and toxicity rates. To quantify the above-described problem, we performed a dose modeling study using a fixed prescription dose at the surface of the applicator and varied tumor response scenarios. METHODS: Endorectal ultrasound-based 3D-volume-models of rectal tumors and the rectal wall were used to simulate the delivered dose to GTV, CTV and the rectal wall layers, assuming treatment with Maastro HDR contact applicator for rectal cancer with a fixed prescription dose to the applicator surface (equivalent to 3 × 30 Gy CXB) and various response scenarios. RESULTS: An identical prescribed dose to the surface of the applicator resulted in a broad range of doses delivered to the GTV, CTV and the uninvolved intestinal wall. For example, the equieffective dose in 2 Gy per fraction (EQD2) D90% of the GTV varied between 63 and 231 Gy, whereas the EQD2 D2cc of the rectal wall varied between 97 and 165 Gy. CONCLUSION: Doses prescribed at the surface are not representative of the dose received by the tumor and the bowel wall. This stresses the relevance of dose reporting and prescription to GTV and CTV volumes and OAR in order to gain insight between delivered dose, local control and toxicity and to optimize treatment protocols.

GEC ESTRO ACROP consensus recommendations for contact brachytherapy for rectal cancer.

PURPOSE: To issue consensus recommendations for contact X-Ray brachytherapy (CXB) for rectal cancer covering pre-treatment evaluation, treatment, dosimetric issues and follow-up. These recommendations cover CXB in the definitive and palliative setting. METHODS: Members of GEC ESTRO with expertise in rectal CXB issued consensus-based recommendations for CXB based on literature review and clinical experience. Levels of evidence according to the Oxford Centre for Evidence based medicine guidance are presented where possible. RESULTS: The GEC ESTRO ACROP consensus recommendations support the use of CXB to increase the chances of clinical complete remission and cure for patients who are elderly with high surgical risk, surgically unfit or refusing surgery. For palliative treatment, the use of CXB is recommended for symptomatic relief and disease control. The use of CXB in an organ-preservation setting in surgically fit patients is recommended within the setting of a clinical trial or registry. CONCLUSIONS: The GEC ESTRO ACROP recommendations for CXB are provided. Recommendations towards standardisation of reporting and prescription are given. Practitioners are encouraged to follow these recommendations and to develop further clinical trials to examine this treatment modality and increase the evidence base for its use. The routine collection of outcomes both clinical and patient-reported is also encouraged.