ESTRO 2021 Abstract Book

S1131

ESTRO 2021

Patients were treated between 2015-2019 and were analyzed in two groups: adjuvant radiotherapy (aRT) group and salvage radiotherapy (sRT) group. Acute and late toxicities were evaluated according to RTOG/EORTC scale. Differences in proportions between groups were analyzed using the Pearson’s Chi-squared test. Univariate logistic regression models predicting rectal and bladder toxicity were used. Results The total number of patients was 129 (aRT:65; sRT: 64), with a median follow-up of 22 months. The characteristics of both groups were reported in Table 1. In both groups prostate bed was delineated according to Radiation Therapy Oncology Group guidelines and total dose 66 Gy (2 Gy/die) was delivered by IMRT/VMAT technique. Grade 1 acute bladder toxicities were reported in 40 (61.5%) and 30 (46.9%) patients and grade 2 toxicities were detected in 1 (1.5%) and 6 (9.4%) patients in aRT and sRT, respectively. Grade 1 late bladder toxicities were described in 30 (46.2%) and 20 (31.2%) patients and grade 2 toxicities were reported in 6 (9.2%) and 2 (3.1%) patients in aRT and sRT, respectively. Acute grade 1 rectal toxicities occurred in 18 (27.7%) aRT patients and 27 (42.2%) sRT patients and 5 (7.7%) and 4 (6.2%) patients developed grade 2 rectal adverse event in aRT and sRT, respectively. Regarding late rectal toxicity, G1 was reported in 10 patients (15.4%), G2 in 6 (9.2%) and G3 in 1 patient (1.5%) in the aRT group. In sRT arm, 8 patients (12.5%) and 1 (1.6%) developed G1 and G2 toxicity, respectively. A statistically significant difference was found for late G1-2 bladder toxicity (55.4% in aRT versus 34.4% in sRT, p =0.041); a similar trend, although not reaching a statistically significant difference was observed for acute G1-2 bladder toxicity (63.1% versus 56.2%, p =0.071). In the univariate logistic regression model sRT was associated with lower rate of bladder late toxicity with OR 0.42 (0.20-0.85, p =0.017).

Conclusion Both groups treated in an adjuvant or salvage setting showed acceptable toxicities. We identified lower acute and late bladder toxicity in patients treated with sRT respect to aRT. The lower toxicity profile of sRT respect to aRT should be considered in the decision between adjuvant and salvage radiotherapy after radical prostatectomy for patients with adverse pathological findings and undetectable PSA level.