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Purpose/Objective(s) Conventional prophylaxis for heterotopic ossification (HO) of the hip with radiotherapy (RT) includes treatment of the prosthesis, adductor, and abductor compartments. To limit RT effects on neovascularization and healing after surgery, we routinely used a limited-field RT (LF-RT), which only includes the affected compartment guided by pre-operative imaging. This study aims to examine whether LF-RT was as effective in preventing local recurrence as CF-RT. Materials/Methods We retrospectively reviewed the charts of 85 consecutive patients who underwent post-operative RT for HO from March 2005 to June 2019. Patients treated to non-hip sites or without radiographic follow-up were excluded. RT fields were reviewed to determine whether they fall under CF-RT defined as inclusion of the prosthesis, adductor, and abductor compartments or LF-RT which was defined as the adductor compartment alone. Results A total of 48 patients were eligible. Most patients were male (60.4%), with a median age of 65 years (interquartile range (IQR) 60-75 years), and a median follow-up of 23.8 months (IQR 12.6-53.1 months). Most patients received 7 Gray (81.3%), with the most common technique being 2-dimensional RT (70.8 %). Thirty-six patients (75%) received LF-RT to the abductor compartment, whereas twelve patients (25%) received CF-RT. There was no significant difference in local recurrence between LF-RT (0%) and CF-RT (8.3%) (P = 0.4). No ipsilateral re-treatment was required in LF-RT patients compared to one CF-RT patient (8.3 %). The single recurrence in the CF-RT group was retreated with CF-RT. There were no recorded acute or late adverse events related to either field. No patient in either group required non-radiation secondary interventions such as hip injections or surgical revision for HO. Conclusion Within this limited cohort, LF-RT was similarly efficacious as CF-RT in prophylaxis for HO of the hip with no added toxicity. Future centers that are interested in adopting LF-RT should routinely acquire pre-operative images to aid in the creation of treatment volumes.

PURPOSE/OBJECTIVE(S) Central (CLT) and ultracentral (UCLT) lung tumors can be at higher risk for treatment related mortality following stereotactic body radiation therapy (SBRT) and the preferred dose and fractionation is unclear. We assessed the toxicity and outcomes of patients with CLT and UCLT who underwent definitive five-fraction SBRT. MATERIALS/METHODS We reviewed the charts of patients with either CLT or UCLT managed with SBRT from June 2010-April 2019. CLT were defined as gross tumor volume within 2 cm of either the proximal bronchial tree, trachea, mediastinum, aorta, or spinal cord. UCLT were defined as GTV abutting any of these structures. Toxicity was graded by the Common Terminology Criteria for Adverse Events version 5.0. Propensity score matching was performed for gender, performance status, and history of prior lung cancer. Survival outcomes evaluated by Cox regression and Kaplan-Meier estimation. RESULTS Within this cohort of 83 patients, the median age was 73.1 years with a median follow up of 29.9 months. All patients underwent 5 fraction SBRT, with dose range of 50-60 Gy. Most patients had T1 tumors (68.7%) and 43 (51.8%) were considered UCLT. In 20 (50%) patients with CLT, the proximal bronchial tree was the closest central structure while the aorta was the closest structure in 16 (37.2%) of UCLT patients. Grade 2+ toxicity was similar between the two groups, 11 (27.5%) for CLT and 13 (30.2%) (P = 0.78) for UCLT patients. Furthermore, there was no difference in grade 3 toxicity with 3 (7.5%) CLT and 4 (9.3%) UCLT patients (P = 0.77) and no observed grade 4+ events. There was no difference in crude local failure (5% vs 7.0%) (P = 0.34) or recurrence rates (22.5% vs 9.3) (P = 0.09). Multivariate analysis adjusting for gender, performance status, prior lung cancer, history of diabetes, history of heart disease, and prescription volume revealed UCLT to be associated with worse overall survival (OS) (P = 0.02) but not freedom from progression (FFP). Using propensity score match pairing, 29 match pairs were generated finding UCLT to correlate with reduced non-cancer related survival (NC-OS) and OS, but not FFP. CONCLUSION Definitive 5 fraction SBRT yielded similar toxicity profiles for CLT and UCLT. Despite no difference in FFP, UCLT were associated with worse (NC-OS) and OS.