Radiation Therapy Treatment Volume and Rectal Dosimetry Predict Clinically Significant Hematochezia in Gantry-Based 5-Fraction Prostate SABR

Abstract

were male (78%) and underwent maximal transurethral resection of bladder tumor prior to RT (90%). Thirty-seven patients (67%) received concurrent chemotherapy; all but 2 of these patients received platinumbased regimens. Most patients (85%) received bladder and pelvic nodal radiation. Thirty-four patients (62%) were treated with intensity modulated RT (IMRT). The median dose to the bladder tumor was 6480 cGy (range 5000-7250 cGy), 1.8 to 2.15 Gy per day, and median dose to the pelvic lymph nodes was 4500 cGy (range 3960-5000 cGy). There were 19 bladder failures (12 biopsy-proven muscle-invasive and 7 superficial/in situ recurrences). Local control at 1 and 2 years was 78% and 69%, respectively. Patient age <80 years was significantly associated with improved local control (PZ.009), whereas gender, treatment modality (IMRT vs 3dimensional), concurrent chemotherapy, and stage had no impact. There were 5 pelvic and 17 distant failures. Freedom from distant failure at 1 and 2 years was 78% and 73%, respectively. The median overall survival was 30 months, and 1and 2-year overall survival rates were 74.5% and 52.7%, respectively. Survival was significantly worse in patients that were unfit for surgery (PZ.02) and those who were unable to get concurrent chemotherapy (PZ.03). Acute, grade 2, urinary, and gastrointestinal (GI) toxicity was seen in 35% and 18% of patients, respectively. Late urinary and GI toxicity (grade 2) was 24% and 2%, respectively. Conclusion: In this elderly cohort of patients with muscle-invasive bladder cancer, the use of definitive RT with or without chemotherapy yielded similar results compared to historic controls. While local control in the first 2 years was good, overall survival in this patient population remains poor. Author Disclosure: C.R. Kreofsky: None. K.W. Merrell: None. C.S. Choo: None. R.W. Mutter: None. T.M. Pisansky: None. B.J. Davis: None. R. Choo: None.