Stereotactic body radiotherapy for patients with relapsing prostate cancer with bones or nodes oligometastases.

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263 Background: To analyze patients treated by stereotactic body radiotherapy (SBRT) for node or bone oligometastatic recurrence of a prostate cancer previously locally treated, To identify possible pronostic factors of early biochemical failure (BF) after SBRT. Methods: We reviewed patients with a rising PSA treated by SBRT between November 2011 and April 2016 for bone or node oligometastases, diagnosed on a 18F Fluorocholine positron emission tomography-computed tomography (PET-CT) following biochemical failure of a prostate cancer after a local curative treatment. Recurrence-free survival (RFS) was the primary end-point defined as the time interval between SBRT and biochemical failure. Biochemical failure was defined as 2 consecutive elevations of PSA with last dosage superior to PSA dosage before treatment, or clinical failure. PSA value before SBRT, location of metastases, number of lesions treated, concomitant androgen deprivation therapy were analyzed to identify pronostic factors of poor response to SBRT. Results: With a median follow-up from time of SBRT of 12 months, we treated 40 patients and 56 metastatic lesions, with a local-control rate of 85%. 19 patients were treated for 1 to 3 bone lesions and 21 patients for 1 to 3 node lesions. 8 patients with bone oligometastases and 13 patients with node oligometastases had a recurrence (p=0.55). The main sites of failure after SBRT were lymph nodes only (7 ; 33%), bone only (7 ; 33 %), and synchronous node and bone (4 ; 19%). A 2nd and 3rdcourse of radiotherapy was delivered in 8 and 1 patients. Median RFS was 345 days (134-426) in the node SBRT group and 494 days (85-877) in the bone SBRT group (p=0.27). On bivariate analysis, a PSA nadir up to 0.51 ng/mL after SBRT was identified as a pronostic factor of a worse RFS (p=0.0038). This result was not confirmed in multivariate analysis (p=0.87). Conclusions: SBRT for node oligometastases showed a non significant lower rate of RFS when compared to SBRT in bone oligometastases. A larger cohort with a longer follow up is needed to determine whether node and bone oligometastases have similar outcomes after SBRT.