e24045 Background: In LPC, ADT may be combined with radiation therapy (RT) for 4-24 months. Post-ADT, a significant proportion of men experience prolonged hypogonadism. TRT can alleviate symptoms and improve metabolic outcomes. Contrary to longstanding concerns, there is no substantial evidence of increased prostate cancer recurrence in patients (pts) treated with single modalities (surgery or RT). However, sparse data ( < 100 cases published to our knowledge) exist regarding recurrence risk of LPC with TRT after prior ADT, where baseline T levels may fall below the androgen receptor saturation point. Methods: We retrospectively abstracted clinical data from hospital records of men with stage I – IVA PC, treated with prior concurrent ADT and RT and subsequently received TRT between January 2014 and September 2023. Extracted data included demographics, cancer diagnosis/staging, ADT/TRT treatment details and PSA and clinical outcomes. The co-primary endpoints were change in PSA and incidence of PC recurrence. Results: 21 pts met criteria. Median age was 77. ISUP Grade Groups (GG) included: GG1: 2, GG2: 2, GG3: 8, GG4: 2, and GG5: 7. AJCC 8th ed. stages were: I: 2, II: 7, III: 7, IV-A: 5. The median duration of prior ADT was 8 months (IQR 5 – 17) and the median interval from RT to TRT was 19 months (IQR: 12 – 44). Prior to TRT, the median testosterone level was 30.5 ng/dL (IQR: 17-76). TRT formulations included: injection: 6, oral: 4, topical: 13. The median follow-up period from the start of TRT was 13 months, and the median duration on TRT was 10 months (IQR: 5-22). TRT was ongoing in 15 (71.4%) pts and discontinued in 6 (28.6%). Reasons for discontinuation included testosterone recovery (1), hospice (not PC related) (2), no perceived benefit (2), MD concern for PSA rise (1). After TRT, the median testosterone level was 336 ng/dL (IQR: 207-462). Median PSA pre- and post-TRT were undetectable and 0.08 ng/dL, respectively. None of the subjects experienced PC recurrence or PC-specific mortality. One pt showed PSA bounce without recurrence. Median BMI was unchanged before (28.3 kg/m2) and after (27.7 kg/m2) TRT (p = 0.48). Due to the nature of the study, quality of life measures and metabolic parameters could not be systematically abstracted. Conclusions: In men with LPC who remained hypogonadal long-term after prior ADT and RT, we found that TRT was not associated with a significant rise in median PSA and no cases of PC recurrence were documented. This included many with a history of very high-risk cancers (eg. GG ≥ 4, Stage ≥ III). This study adds to the sparse existing literature in this clinical setting and together they support the case for a prospective trial utilizing TRT in patients who remain hypogonadal after ADT and radiation.
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