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Prostate cancer is driven by androgen receptor (AR) signaling, and radiotherapy (RT) with or without androgen deprivation therapy (ADT) offers a second opportunity at cure for men with local or biochemical recurrence after prostatectomy. In the metastatic setting, AR RNA splice variants (ARVs), including ligand-independent AR-V7, modulate ADT response and tumor radiosensitivity. Here, we hypothesized that ARVs in primary prostate cancer may likewise modulate response to subsequent salvage RT+ADT. We performed ultra-deep RNA-seq of the AR transcript pool from prostatectomy specimens from 43 men who later received salvage RT+ADT. Eighty-six percent of patients had detectable ARVs (median 3, range 0-12). Of the thirty-two unique ARVs detected, only AR-V7 (present in 14% of patients) was associated with outcomes after salvage RT+ADT (HR for second biochemical failure, 6.2, 95% CI 2.3-16.5, p=0.0003). These results suggest for the first time that AR-V7 may modulate outcomes for localized in addition to metastatic prostate cancer.