Rectal deformation management with IGRT in prostate radiotherapy: Can it be managed with rigid alignment alone?

PURPOSE: It is challenging to achieve appropriate target coverage of the prostate with Image Guided Radiation Therapy (IGRT) while simultaneously constraining rectal doses within planned values when there is significant variability in rectal filling and shape. We investigated if rectum planning goals can be fulfilled using rigid CBCT-based on-board alignment to account for interfraction rectal deformations. METHODS: Delivered rectal doses corresponding to prostate alignment ("PR") and anterior rectum alignment ("AR") for 239 daily treatments from 13 patients are reported. Rectal doses were estimated by rigidly mapping the planned dose on the daily CT derived from the daily CBCT according to respective alignment shifts. Rectum V95% (rV95%) was used for analyses. RESULTS: Compared to "PR", "AR" alignment increased rV95% for an average of 34.4% across all patients. rV95% (cc) averaged over all fractions was significant from planning values for 10/13 patients for "PR" and for 9/13 for "AR". 3/13 patients had reproducible anatomy. Of patients with non-reproducible anatomy, three had dosimetrically more favorable, while seven had less favorable anatomies. Most shift differences (82.3%) between the "PR" and "AR" alignments larger than 2 mm resulted in rV95% changes larger than 2 cc. Most shift differences (82.2%) of 2 mm or less between the "PR" and "AR" alignments resulted in rV95% changes less than 2 cc. The average percentage of fractions among patients in which anterior or posterior shifts for "AR" and "PR" alignment was larger than the PTV margins was 9.1% (0.0%-37.5%) and 1.3% (0%-10%). CONCLUSION: Rectal deformation and subsequent inconsistent interfraction separation between prostate and rectal wall translate into anatomical changes that cannot always be mitigated with rigid alignment. If systematic differences exist due to a non-reproducible planning anatomy, attempts to restore the planned rectal doses through anterior rectum alignment produce rather small improvements and may result in unacceptable target underdosage.

Patient Survival With and Without Radiation Therapy for Early-Stage Diffuse Large B-Cell Lymphoma in the Era of PET and Rituximab.

Purpose: The benefit of radiation therapy (RT) becomes uncertain in the treatment of early stage diffuse large B-cell lymphoma (DLBCL) in the era of rituximab, positron emission topography (PET), and computed tomography (CT). We sought to retrospectively review modern patients with early stage I-II DLBCL treated with rituximab and staged by PET-CT to better define which patients benefit from consolidative RT. Methods and Materials: Patients with early stage I-II DLBCL from 1998 to 2017 were reviewed coinciding with our institutional utilization of rituximab with the standard regimen of cyclophosphamide, doxorubicin, vincristine, and prednisone and PET-CT. Relevant clinical information was used to calculate National Comprehensive Cancer Network international prognostic index (IPI) scores. Kaplan-Meier survival analysis and a Cox proportional hazards model were used for overall survival (OS). Results: Seventy-seven patients received chemoimmunotherapy alone, and 41 received chemoimmunotherapy plus RT. Median follow-up time was 9.5 years. On univariate analysis, extranodal disease (P = .04) and National Comprehensive Cancer Network IPI (P < .001) were significantly correlated with OS. Five-year OS was 87% versus 67%, and 10-year OS was 67% versus 58%, numerically higher favoring RT (P = .16). On multivariate Cox regression analysis of OS controlling for IPI and extranodal disease, the addition of RT was associated with improved OS (hazard ratio of 0.4, P = .01). Conclusions: The current analysis supports the use of consolidative RT in early stage DLBCL given an OS benefit on multivariate analysis. Further prospective randomized data are needed to confirm these findings.

Influence of extracellular volume fraction on peak exercise oxygen pulse following thoracic radiotherapy.

BACKGROUND: Radiation-induced myocardial fibrosis increases heart failure (HF) risk and is associated with a restrictive cardiomyopathy phenotype. The myocardial extracellular volume fraction (ECVF) using contrast-enhanced cardiac magnetic resonance (CMR) quantifies the extent of fibrosis which, in severe cases, results in a noncompliant left ventricle (LV) with an inability to augment exercise stroke volume (SV). The peak exercise oxygen pulse (O2Pulse), a noninvasive surrogate for exercise SV, may provide mechanistic insight into cardiac reserve. The relationship between LV ECVF and O2Pulse following thoracic radiotherapy has not been explored. METHODS: Patients who underwent thoracic radiotherapy for chest malignancies with significant incidental heart dose (≥5 Gray (Gy), ≥10% heart) without a pre-cancer treatment history of HF underwent cardiopulmonary exercise testing to determine O2Pulse, contrast-enhanced CMR, and N-terminal pro-brain natriuretic peptide (NTproBNP) measurement. Multivariable-analyses were performed to identify factors associated with O2Pulse normalized for age/gender/anthropometrics. RESULTS: Thirty patients (median [IQR] age 63 [57-67] years, 18 [60%] female, 2.0 [0.6-3.8] years post-radiotherapy) were included. The peak VO2 was 1376 [1057-1552] mL·min- 1, peak HR = 150 [122-164] bpm, resulting in an O2Pulse of 9.2 [7.5-10.7] mL/beat or 82 (66-96) % of predicted. The ECVF, LV ejection fraction, heart volume receiving ≥10 Gy, and NTproBNP were independently associated with %O2Pulse (P < .001). CONCLUSIONS: In patients with prior radiotherapy heart exposure, %-predicted O2Pulse is inversely associated markers of diffuse fibrosis (ECVF), ventricular wall stress (NTproBNP), radiotherapy heart dose, and positively related to LV function. Increased LV ECVF may reflect a potential etiology of impaired LV SV reserve in patients receiving thoracic radiotherapy for chest malignancies.

Favorable Biochemical Freedom From Recurrence With Stereotactic Body Radiation Therapy for Intermediate and High-Risk Prostate Cancer: A Single Institutional Experience With Long-Term Follow-Up.

Purpose/Objective(s): The current study reports long-term overall survival (OS) and biochemical freedom from recurrence (BFFR) after stereotactic body radiation therapy (SBRT) for men with intermediate and high-risk prostate cancer in a single community hospital setting with early adoption. Materials/Methods: Ninety-seven consecutive men with intermediate and high-risk prostate cancer treated with SBRT between 2007 and 2015 were retrospectively studied. Categorical variables for analysis included National Comprehensive Cancer Network risk group, race, Gleason grade group, T stage, use of androgen deprivation therapy, and planning target volume dose. Continuous variables for analysis included pretreatment prostate-specific antigen (PSA), percent cores positive, age at diagnosis, PSA nadir, prostate volume, percent prostate that received 40 Gy, and minimum dose to 0.03 cc of prostate (Dmin). BFFR was assessed using the Phoenix nadir +2 definition. OS and BFFR were estimated using Kaplan-Meier (KM) methodology with comparisons accomplished using log-rank statistics. Multivariable analysis (MVA) was accomplished with a backwards selection Cox proportional-hazards model with statistical significance taken at the p < 0.05 level. Results: Median FU is 78.4 months. Five- and ten-year OS KM estimates are 90.9 and 73.2%, respectively, with 19 deaths recorded. MVA reveals pretreatment PSA (p = 0.032), percent prostate 40 Gy (p = 0.003), and race (p = 0.031) were predictive of OS. Five- and nine-year BFFR KM estimates are 92.1 and 87.5%, respectively, with 10 biochemical failures recorded. MVA revealed PSA nadir (p < 0.001) was the only factor predictive of BFFR. Specifically, for every one-unit increase in PSA nadir, there was a 4.2-fold increased odds of biochemical failure (HR = 4.248). No significant differences in BFFR were found between favorable intermediate, unfavorable intermediate, and high-risk prostate cancer (p = 0.054) with 7-year KM estimates of 96.6, 81.0, and 85.7%, respectively. Conclusions: Favorable OS and BFFR can be expected after SBRT for intermediate and high-risk prostate cancer with non-significant differences seen for BFFR between favorable intermediate, unfavorable intermediate, and high-risk groups. Our 5-year BFFR compares favorably with the HYPO-RT-PC trial of 84%. PSA nadir was predictive of biochemical failure. This study is ultimately limited by the small absolute number of high-risk patients included.

Repeat Thoracic Stereotactic Body Radiation Therapy (SBRT) for Nonsmall Cell Lung Cancer: Long-Term Outcomes, Toxicity, and Dosimetric Considerations.

PURPOSE: Lung reirradiation for nonsmall cell lung cancer (NSCLC) is common for either recurrent disease or new primary cancer. Dose volume tolerance of the lung after multiple courses of radiation therapy (RT) is unknown. We review our experience with lung reirradiation for patients with NSCLC in a single community setting using stereotactic body radiation therapy (SBRT) to report lung cumulative doses, survival, and toxicity. METHODS AND MATERIALS: Forty-four patients who received at least 2 curative courses of lung RT with the second course delivered between January 2012 and December 2017 were eligible. All patients had NSCLC and were treated with SBRT for reirradiation. Cumulative lung dose volume histograms for all courses were generated, summated, and converted into cumulative equivalent dose in 2 Gy fractions (EQD2). Actuarial overall survival (OS), local control, and toxicity is reported, including a subset of patients who received more than 2 courses of SBRT. RESULTS: Median age of the group was 71 years (range, 51-87). Median survival of the entire group from diagnosis, first, and second courses of RT was 3.94, 3.03, and 2.03 years. Three-year actuarial OS for the entire group was 34.1% from second course of RT. The mean EQD2 Gy3 mean lung dose for all courses was 12.35 Gy (range, 2.7-26.52). The mean EQD2 Gy3 V5Gy, V10Gy, V20Gy, V30Gy, and V40Gy were 40.9%, 25.5%, 14.7%, 10.2%, and 7.7%. Six-year actuarial freedom from grade ≥3 complications was 86.3%. The rate of grade ≥3 lung toxicity was 4.5% (2 of 44). Other late toxicities included grade 3 recurrent laryngeal nerve damage (n = 1) and grade 3 chest wall pain/rib fracture (n = 1). Overall, 32% of patients had more than 2 courses of RT to the lung (range, 3-7). CONCLUSIONS: Long-term OS is possible with multiple RT courses to the lung for NSCLC with low toxicity.

Moderately Hypofractionated Intensity Modulated Radiation Therapy With Simultaneous Integrated Boost for Prostate Cancer: Five-Year Toxicity Results From a Prospective Phase I/II Trial.

BACKGROUND: In this phase I/II trial, 5-year physician-assessed toxicity and patient reported quality of life data is reported for patients undergoing moderately hypofractionated intensity modulated radiation therapy (IMRT) for prostate cancer using a simultaneous integrated boost (SIB) and pelvic lymph node (LN) coverage. MATERIALS AND METHODS: Patients with T1-T2 localized prostate cancer were prospectively enrolled, receiving risk group based coverage of prostate ± seminal vesicles (SVs) ± pelvic lymph nodes (LNs). Low risk (LR) received 69.6 Gy/29 fractions to the prostate, while intermediate risk (IR) and high risk (HR) patients received 72 Gy/30fx to the prostate and 54Gy/30fx to the SVs. If predicted risk of LN involvement >15%, 50.4 Gy/30fx was delivered to pelvic LNs. Androgen deprivation therapy was given to IR and HR patients. RESULTS: There were 55 patients enrolled and 49 patients evaluable at a median follow up of 60 months. Included were 11 (20%) LR, 23 (41.8%) IR, and 21 (38.2%) HR patients. Pelvic LN treatment was given in 25 patients (51%). Prevalence rates of late grade 2 GI toxicity at 1, 3, and 5 years was 5.8, 3.9, and 5.8%, respectively, with no permanent grade 3 events. Prevalence rates of late grade 2 GU toxicity at 1, 3, and 5 years rates were 15.4, 7.7, and 13.5%, respectively, with three grade 3 events (5.8%). The biochemical relapse free survival at 5 years was 88.3%. There were no local, regional, or distant failures, with all patients still alive at last follow up. CONCLUSION: Moderate hypofractionation of localized prostate cancer utilizing a SIB technique and LN coverage produces tolerable acute/late toxicity. Given equivalent efficacy between moderate hypofractionation schedules, the optimal regimen will be determined by long-term toxicity reported from both the physician and patient perspective. CLINICAL TRIAL REGISTRATION: www.ClinicalTrials.gov, identifier NCT01117935, Date of Registration: 5/6/2010.

Cardiac MRI utilizing late gadolinium enhancement (LGE) and T1 mapping in the detection of radiation induced heart disease.

BACKGROUND AND PURPOSE: Radiotherapy has been associated with late dose-dependent cardiovascular toxicity. In this cross-sectional pilot study, radiation dose distributions were correlated with areas of localized and diffuse myocardial fibrosis as measured by novel cardiac MRI (CMR) sequences including late gadolinium enhancement (LGE) and T1 mapping with the goal to identify early markers of myocardial damage. MATERIALS AND METHODS: Twenty-eight patients with chest tumors including lung, breast, esophagus, and lymphoma underwent CMR per study protocol on average 46.4 months (range 1.7-344.5) after radiotherapy. Patients without pretreatment cardiac history were included if the volume of heart receiving 5 Gy or more was at least 10% (V5Gy ≥ 10%). The association of LGE with cardiac dosimetric factors, clinical factors (e.g., tumor type, smoking history, BMI), and T1 values was analyzed. RESULTS: Cardiac maximum (Dmax) and mean dose (Dmean) equivalent to doses delivered in 2 Gy fractions (EQD2) were on average 50.9 Gy (range 6.2-108.0) and 8.2 Gy (range 1.0-35.7), respectively, compared to 60.8 Gy (40.8-108.0) and 6.8 Gy (1.8-21.8) among the 9 patients with LGE. Doses were not different between patients with and without LGE (p = 0.16 and 0.56, respectively). The average T1 value of the left ventricle myocardium was 1009 ms (range 933-1117). No significant correlation was seen for heart Dmax and Dmean and T1 values (p = 0.14 and 0.58, respectively). In addition, no significant association between clinical factors and the development of LGE was identified. CONCLUSIONS: No relation between cardiac doses, the presence of LGE or T1 values was observed. Further study is needed to determine the benefit of CMR for detecting radiotherapy-related myocardial fibrosis.

Propensity Score Matched Comparison of Intensity Modulated Radiation Therapy vs Stereotactic Body Radiation Therapy for Localized Prostate Cancer: A Survival Analysis from the National Cancer Database.

PURPOSE: No direct comparisons between extreme hypofractionation and conventional fractionation have been reported in randomized trials for the treatment of localized prostate cancer. The goal of this study is to use a propensity score matched (PSM) analysis with the National Cancer Database (NCDB) for the comparison of stereotactic body radiation therapy (SBRT) and intensity modulated radiation therapy (IMRT) for organ confined prostate cancer. METHODS: Men with localized prostate cancer treated with radiation dose ≥72 Gy for IMRT and ≥35 Gy for SBRT to the prostate only were abstracted from the NCDB. Men treated with previous surgery, brachytherapy, or proton therapy were excluded. Matching was performed to eliminate confounding variables via PSM. Simple 1-1 nearest neighbor matching resulted in a matched sample of 5,430 (2,715 in each group). Subset analyses of men with prostate-specific antigen (PSA) > 10, GS = 7, and GS > 7 yielded matched samples of 1,020, 2,194, and 247, respectively. RESULTS: No difference in survival was noted between IMRT and SBRT at 8 years (p = 0.65). Subset analyses of higher risk men with PSA > 10 or GS = 7 histology or GS > 7 histology revealed no difference in survival between IMRT and SBRT (p = 0.58, p = 0.68, and p = 0.62, respectively). Variables significant for survival for the matched group included: age (p < 0.0001), primary payor (p = 0.0001), Charlson/Deyo Score (p = 0.0002), PSA (p = 0.0013), Gleason score (p < 0.0001), and use of hormone therapy (p = 0.02). CONCLUSION: Utilizing the NCDB, there is no difference in survival at 8 years comparing IMRT to SBRT in the treatment of localized prostate cancer. Subset analysis confirmed no difference in survival even for intermediate- and high-risk patients based on Gleason Score and PSA.

Single Institutional Experience of Stereotactic Radiosurgery Alone for First Brain Metastatic Event and Salvage of Second Brain Metastatic Event in a Community Setting with Review of the Literature.

PURPOSE: To document survival for patients treated with stereotactic radiosurgery (SRS) alone for brain metastases either at initial presentation or for salvage in conjunction with other known prognostic factors in a single institutional community setting with comparison to current literature. METHODS: All patients treated for brain metastases with SRS between October 2006 and October 2013 were reviewed. We identified 91 patients treated with SRS alone for first brain metastatic event (FBME) and 87 patients treated with SRS for second brain metastatic event (SBME). We excluded the 14 patients treated with SRS for both FBME and SBME to satisfy the independence assumption for comparison of groups. Patient demographics, including age, gender, primary cancer type, presence of extracranial metastases, number of brain metastases, initial site of metastases (brain vs. other), recursive partitioning analysis (RPA), and Karnofsky Performance status (KPS) were documented. RESULTS: There were no significant differences in overall survival for patients treated with SRS for FBME compared with SBME (log-rank p = 0.9347). Univariate and multivariable Cox regression modeling revealed KPS (p = 0.0003) and RPA (p = 0.0143) were the only independent prognostic factors for survival. Specifically, patients with RPA 1 had a 61% decreased risk of death compared to those with RPA 3. Patients with RPA 2 had a 33% decreased risk of death compared to those with RPA 3. The 1-year survival rate was 36.5% for patients with RPA1, 33.3% for those with RPA 2, and 17.1% for those with RPA 3. Patients with KPS 90-100 had a 62% decreased risk of death compared to those with KPS < 70. The 1-year survival rate for patients KPS 90-100, 70-80, and <70 were 60.7, 24.6, and 16.7%, respectively. CONCLUSION: No difference in survival was noted for FBME and SBME with performance status, the single most important prognostic factor following SRS. Aggressive treatment should be considered for patients with good performance status regardless if presenting with FBME or SBME. Our results are consistent with single, multi-institutional, and randomized trials after literature review.

Lung metastases treated with stereotactic body radiotherapy: the RSSearch® patient Registry's experience.

OBJECTIVES: To report overall survival and local control for patients identified in the RSSearch® Patient Registry with metastatic cancer to the lung treated with SBRT. METHODS: Seven hundred two patients were identified with lung metastases in the RSSearch® Registry. Of these patients, 577 patients had SBRT dose and fractionation information available. Patients were excluded if they received prior surgery, radiation, or radiofrequency ablation to the SBRT treated area. Between April 2004-July 2015, 447 patients treated with SBRT at 30 academic and community-based centers were evaluable for overall survival (OS). Three hundred four patients with 327 lesions were evaluable for local control (LC). All doses were converted to Monte Carlo equivalents and subsequent BED Gy10 for dose response analysis. RESULTS: Median age was 69 years (range, 18-93 years). Median Karnofsky performance status (KPS) was 90 (range 25/75% 80-100). 49.2% of patients had prior systemic therapy. Median metastasis volume was 10.58 cc (range 25/75% 3.7-25.54 cc). Site of primary tumor included colorectal (25.7%), lung (16.6%), head and neck (11.4%), breast (9.2%), kidney (8.1%), skin (6.5%) and other (22.1%). Median dose was 50 Gy (range 25/75% 48-54) delivered in 3 fractions (range 25/75% 3-5) with a median BED of 100Gy10 (range 25/75% 81-136). Median OS for the entire group was 26 months, with actuarial 1-, 3-, and 5-year OS of 74.1%, 33.3, and 21.8%, respectively. Patients with head and neck and breast cancers had longer median OS of 37 and 32 months respectively, compared to colorectal (30 months) and lung (26 months) which corresponded to 3-year actuarial OS of 51.8 and 47.9% for head and neck and breast respectively, compared to 35.8% for colorectal and 31.2% for lung. The median LC for all patients was 53 months, with actuarial 1-, 3-, and 5-year LC rates of 80.4, 58.9, and 46.3%, respectively. There was no difference in LC by primary histologic type (p = 0.49). Improved LC was observed for lung metastases that received SBRT doses of BED ≥100Gy10 with 3-year LC rate of 77.1% compared to 45% for lung metastases treated with BED < 100Gy10 (p = 0.01). Smaller tumor volumes (<11 cc) had improved LC compared to tumor volumes > 11 cc. (p = 0.005) Two-year LC rates for tumor volumes < 11 cc, 11-27 cc and > 27 cc were 72.9, 64.2 and 45.6%, respectively. This correlated with improved OS with 2-year OS rates of 62.4, 60.9 and 46.2% for tumor volumes < 11 cc, 11-27 cc and > 27 cc, respectively (p = 0.0023). In a subset of patients who received BED ≥100Gy10, 2-year LC rates for tumor volumes < 11 cc, 11-27 cc and > 27 cc were 82.8, 58.9 and 68.6%, respectively (p = 0.0244), and 2-year OS rates were 66.0, 58.8 and 28.5%, respectively (p = 0.0081). CONCLUSION: Excellent OS and LC is achievable with SBRT utilizing BED ≥100Gy10 for lung metastases according to the RSSearch® Registry data. Patients with small lung metastases (volumes < 11 cc) had better LC and OS when using SBRT doses of BED ≥100Gy10. Further studies to evaluate a difference, if any, between various tumor types will require a larger number of patients.

Survival and Control Prognosticators of Recurrent Gynecological Malignancies of the Pelvis and Para-aortic Region Treated with Stereotactic Body Radiation Therapy.

PURPOSE: To define prognostic factors associated with improved survival and local control (LC) for gynecologic cancer recurrences limited to the pelvis and para-aortic (PA) region using stereotactic body radiation therapy (SBRT). METHODS: Between 2/2008 and 7/2014, 30 women (35 targets) with pelvic or PA recurrence of endometrioid (n = 12), cervical (n = 11), ovarian (n = 3), uterine-serous (n = 2), or carcinosarcoma (n = 2) cancer were treated with SBRT. Eleven recurrences were located in the central pelvis, 11 along the pelvic sidewall (PSW), and 13 in the PA region. RESULTS: Five-year survival for all patients was 42% with a median survival of 43.4 months. Multivariate analysis revealed better performance status (PS), and smaller clinical tumor volume was significant for improved survival (p < 0.05). CONCLUSION: SBRT is a local therapy for recurrent gynecological malignancies in the pelvis and PA region with curative potential. SBRT is especially effective for LC when targeting PSW or PA recurrence and for patients with a cervical/endometrioid uterine primary. Survival is improved for patients with better PS and smaller recurrence volume prior to SBRT.

The Comparison of Stereotactic Body Radiation Therapy and Intensity-Modulated Radiation Therapy for Prostate Cancer by NCCN Risk Groups.

OBJECTIVES: The primary objective of this study is to compare freedom from biochemical failure (FFBF) between stereotactic body radiation therapy (SBRT) and intensity-modulated radiation therapy (IMRT) for patients with organ confined prostate cancer treated between 2007 through 2012 utilizing the 2015 National Comprehensive Cancer Network (NCCN) risk stratification guidelines. A secondary objective is to compare our updated toxicity at last follow-up compared with pretreatment with respect to bowel, bladder, sexual functioning, and need for invasive procedures between the two groups. METHODS: We retrospectively reviewed 270 consecutive men treated with either SBRT (n = 150) or IMRT (n = 120) at a community hospital with two distinct radiation departments and referral patterns. Charts were reviewed for pretreatment and treatment factors including race, age, clinical T stage, initial PSA, Gleason score, use of androgen deprivation therapy, treatment with SBRT vs. IMRT, as well as stratification by 2015 NCCN guidelines. Kaplan-Meier (KM) methodology was used to estimate FFBF, with statistical comparisons accomplished using log rank tests. Multivariable Cox proportional hazard modeling was used to establish independent factors prognostic of biochemical failure. Descriptive statistics were used to describe toxicity graded by a modified Radiation Therapy Oncology Group (RTOG) late radiation morbidity scoring system. RESULTS: Significant prognostic factors in univariate analysis for FFBF included NCCN risk groups (p = 0.0032), grade (p = 0.019), and PSA (p = 0.008). There was no significant difference in FFBF between SBRT vs. IMRT (p = 0.46) with 6-year actuarial FFBF of 91.9% for SBRT and 88.9% for IMRT. Multivariable analysis revealed only the NCCN risk stratification to be significant predictor for FFBF (p = 0.04). Four-year actuarial FFBF by NCCN risk stratification was 100% very low risk, 100% low risk, 96.5% intermediate risk, 94.5% high risk, and 72.7% very high risk. There were no grade 3 gastrointestinal or genitourinary toxicities for either SBRT or IMRT at last follow-up. CONCLUSION: No significant difference in FFBF was found between SBRT and IMRT for organ confined prostate cancer in multivariable analysis within this retrospective data set. Overall toxicity was low. The 2015 NCCN risk stratification was validated in this population and was the only significant factor for FFBF in multivariable analysis.

ASTRO APEx® and RO-ILS™ are applicable to medical malpractice in radiation oncology.

AIM: To analyze malpractice trials in radiation oncology and assess how ASTRO APEx® and RO-ILS™ apply to such cases. METHODS: The Westlaw database was reviewed using PICOS/PRISMA methods. Fisher's exact and Mann-Whitney U tests were used to find factors associated with outcomes. RESULTS: Of 34 cases identified, external beam was used in 26 (77%). The most common factors behind malpractice were excessive toxicity (80%) and lack of informed consent (66%). ASTRO APEx pillars and ROI-LS had applicability to all but one case. Factors favoring the defendant included statute of limitations (odds ratio: 8.1; 95% CI: 1.3-50); those favoring the plaintiff included patient death (odds ratio: 0.7; 95% CI: 0.54-0.94). CONCLUSION: APEx and RO-ILS are applicable to malpractice trials in radiation oncology.