Extended followup oncologic outcome of randomized trial between cryoablation and external beam therapy for locally advanced prostate cancer (T2c-T3b)

Abstract

Purpose: We assessed and compared the survival outcomes between cryoablation and external beam radiation therapy in patients with locally advanced prostate cancer (cT2c-cT3b).

Materials and methods: Patients with locally advanced prostate cancer, recruited from 1999 to 2002, were randomized to primary cryoablation or external beam radiotherapy. All patients received neoadjuvant hormonal therapy for 3 months before and 3 months after the procedures. Patients underwent followup transrectal ultrasound guided biopsy (at 3, 6, 12, 18 and 24 months for cryoablation, and at 18 and 24 months for external beam radiotherapy) and as clinically indicated thereafter. Biochemical failure was based on the Phoenix criterion (prostate specific antigen nadir +2 ng/dl).

Results: A total of 62 patients completed the trial. Median followup was 105.2 months (SD ±35.8). Accrual was limited due to newer data favoring longer neoadjuvant hormonal therapy and higher external beam radiotherapy dose for locally advanced prostate cancer. There was a greater reduction in prostate volume in the cryoablation group after intervention (-54% vs -34%, p ≤0.01). Disease specific survival and overall survival were comparable between the groups. However, the 8-year biochemical disease-free survival rate was significantly lower in the cryoablation group (17.4% vs 59.1%) (p = 0.01).

Conclusions: This randomized trial with median followup approaching 9 years showed that cryoablation was inferior in attaining biochemical disease-free survival in patients with locally advanced prostate cancer (cT2c-T3). Cryoablation may be more suited for less bulky prostate cancer. Longer duration neoadjuvant hormonal therapy or a multimodal approach may provide optimal biochemical disease-free survival in this patient population.