Metronomic cyclophosphamide therapy in hormone-naive patients with non-metastatic biochemical recurrent prostate cancer: a phase II trial

After curative local therapy, biochemical recurrence is a mode of relapse among patient with prostate cancer (PC). Deferring androgen deprivation therapy (ADT) or offering non-hormonal therapies may be an appropriate option for these non-symptomatic patients with no proven metastases. Metronomic cyclophosphamide (MC) has shown activity in metastatic PC setting and was chosen to be assessed in biochemical relapse. This prospective single-arm open-label phase II study was conducted to evaluate MC regimen in patients with biochemical recurrent PC. MC was planned to be administered orally at a daily dose of 50 mg for 6 months. Primary endpoint was PSA response. Thirty-eight patients were included and treated. Median follow-up was 45.5 months (range 17-100). Among them, 14 patients (37 %) achieved PSA stabilisation and 22 patients (58 %) experienced PSA progression. Response rate was 5 % with one complete response (2.6 %), and 1 partial response with PSA decrease >50 % (2.6 %). The median time until androgen deprivation therapy initiation was around 15 months. The treatment was well tolerated. Neither grade 3-4 toxicity nor serious adverse events were observed. This first prospective clinical trial with MC therapy in patients with non-metastatic biochemical recurrence of PC displayed modest efficacy when measured with PSA response rate, without significant toxicity. It might offer a new safe and non-expensive option to delay initiation of ADT. These results would need to be confirmed with larger prospective randomised trials.