Local failure is a dominant mode of recurrence in locally advanced and clinical node positive prostate cancer patients treated with combined pelvic IMRT and androgen deprivation therapy

Background: The recurrence patterns of high-risk, N1 prostate cancer after radiation therapy (RT) including the pelvic lymph nodes have not been fully investigated. Material and methods: We have a prospective clinical study since 2004 that has followed 138 men with locally advanced prostate cancer (T1-T4N0-N1M0) treated with definitive RT encompassing the prostate and pelvic lymph nodes and long-term androgen deprivation therapy (ADT). Forty nine of the 52 patients that developed recurrence were imaged at biochemical failure to detect the site of recurrence. Results: Imaging identified the site of recurrence in 46 patients. Twenty five patients had prostatic recurrence only, none had local lymph node recurrence only, 11 had distant metastases only, 7 had prostatic recurrence and distant metastases, 2 had prostatic recurrence, local nodal recurrence and distant metastases, and 1 had local nodal recurrence with distant metastases. The mean time to recurrence was 62 months for prostate only, 40 months for distant only and 50 months for prostate and distant recurrence. There was a 69% recurrence rate for patients with magnetic resonance imaging -detected N1 disease. There was significantly longer survival for patients with prostate recurrence only compared to patients with distant recurrence (P < 0.018). Five-year prostate cancer-specific survival were 85% for prostate only, 44% for distant only and 48% for prostate and distant recurrence (prostate only vs. distant only; P = 0.008, prostate only vs. prostate and distant; P = 0.018, distant vs. prostate and distant; P = 0.836). Conclusions: The predominant recurrence pattern for high-risk, N1 prostate cancer was prostatic recurrence and distant spread after pelvic RT and androgen deprivation therapy. Our data argue for further local dose escalation and pelvic nodal radiation to prevent recurrence in these sites. Lymph node metastasis at initial staging with an magnetic resonance imaging was a strong predictor of recurrence and poor survival and may identify patients in need of more aggressive treatment.