ESTRO 2023 - Abstract Book

S1199

Digital Posters

ESTRO 2023

to the duration of hormone therapy in breast cancer. Our aim was to examine time to testosterone recovery following long course LHRH agonists and explore whether delayed or failure of testosterone recovery influences PCa outcomes. Materials and Methods Data from 473 patients in the Pelvic IMRT Clinical Trial in Prostate Cancer were analysed. All patients received radiotherapy and a planned 3 years of hormone therapy for high-risk PCa. Subsequent testosterone levels and PCa outcomes were recorded. Results 376 patients were included (reasons for exclusion: PCa progression or death during hormone therapy, patient received androgen receptor antagonists alone, no testosterone levels recorded). Median follow up was 9 years, 2 months. Median time to recovery of testosterone to 10nmol/L from cessation of LHRH agonists was 53 months, with 173 patients (46%) ultimately achieving this (median time to and percent achieving levels of 6nmol/L and 2nmol/L were 22 months and 67%, 14 months and 88% respectively). Patients over the age of 65 had a longer median time to recovery to 10nmol/L (30 months in under-65s vs 106 months in over-65s, p<0.001). Median time to PCa recurrence was 125 months; 167 patients (44%) had experienced a recurrence at the time of data collection. Patients who failed to recover testosterone to 10nmol/L had a nonsignificant trend towards a longer time to recurrence (p=0.074, median time not reached vs 113 months). Similar trends were observed for 2nmol/L and 6nmol/L. Of the 173 patients who recovered to 10nmol/L, those who took more than two years to recover had a longer time to recurrence than those who recovered within two years (median 166 months vs 100 months, p=0.008) and a longer recurrence-free survival (130 months vs 96 months, p=0.002). Time to second line therapy from cessation of LHRH agonists between the groups was analysed to see if the longer time to recurrence was associated with the development of castration resistance in the delayed group. There was no difference in time to second line therapy between groups (p=0.98). Conclusion Testosterone recovery following long-course LHRH agonists is often delayed or absent, particularly in older patients, and patients should be counselled appropriately. Patients with delayed or absent testosterone recovery appeared to have delayed PCa recurrence, but such recurrences were associated with castration resistance, supported by the observation that there was no difference in time to second line therapy between patients with or without delayed recovery. Testosterone supplementation may be considered for men with ongoing andropausal symptoms and delayed testosterone recovery. 1 Seoul National University Hospital, Department of Radiation Oncology, Seoul, Korea Republic of; 2 Kyung Hee University Hospital at Gangdong, Department of Radiation Oncology, Seoul, Korea Republic of; 3 Seoul National University Bundang Hospital, Department of Radiation Oncology, Seong-nam si, Korea Republic of Purpose or Objective Extrapolating from the research on pathologically lymph node positive prostate cancer, the benefits of definitive radiotherapy (RT) for clinically lymph node positive prostate cancer may be limited to specific patients, but adequate subgroups have not yet been clearly defined. Materials and Methods This study aimed to analyze the survival outcomes and prognostic factors in 62 patients of clinically lymph node positive prostate cancer treated with definitive RT between 2000 and 2020. Also, we investigated subgroups that could benefit from addition of definitive RT to androgen deprivation therapy (ADT). All patients received definitive RT (median 79Gy, range 70-80Gy) and 46.8% of patients received ADT more than 24 months. Results At a median follow up of 31 months, ADT duration ≥ 24 months (p=0.039, HR 0.25) and positive biopsy core ≥ 75% (p=0.037, HR 5.60) showed significant relationships with distant metastasis free survival. Regarding overall survival (OS), ADT duration ≥ 24 months (p=0.003, HR 0.06) and number of lymph node (LN) metastases ≥ 4 (p=0.03, HR 7.77) were significant factors. In the subgroup analysis, patients were divided into three risk groups. The low-risk group was defined as having less than 4 LN metastases and receiving ADT for more than 24 months, the high-risk group as having 4 or more LN metastases and less than 24 months of receiving ADT, and the intermediate-risk group as all remaining cases. The 3-year actuarial OS rate was 100%, 93.3%, and 45.7% for low-, intermediate-, high-risk groups, respectively. There was no death in the low risk group during the entire follow up period. PO-1481 Clinical outcomes of clinically node positive prostate cancer patients after definitive radiotherapy T.H. Kim 1 , D. Kim 2 , J. Kim 3