Salvage radiation therapy (SRT) prior to salvage hormone therapy (SHT) is more beneficial than SHT alone for men with PSA failure after radical prostatectomy (RP), according to clinical trial results published in European Urology.

Biochemical recurrence in the absence of evidence of tumor presents a quandary because it is unknown whether patients harbor local or metastatic disease. The former benefits more from SRT and the latter from SHT, most commonly androgen deprivation therapy (ADT).

In a phase 3 trial (JCOG0401), investigators randomly assigned 210 Japanese men with localized prostate cancer whose PSA levels increased to 0.4 to 1.0 ng/mL after RP to receive SHT (80 mg bicalutamide, followed by luteinizing hormone-releasing hormone agonist if bicalutamide failed) or SRT (64.8 Gy to the prostatic bed, followed by the same hormone regimen if radiation failed).

Time to bicalutamide failure, the primary end point, was significantly longer in the SRT group: 8.6 vs 5.6 years, Seiji Naito, MD, PhD, of Harasanshin Hospital in Fukuoka, Japan, and colleagues reported. In addition, 31% of patients in the SRT group were successfully treated with radiation and required no SHT. Overall, clinical relapse-free survival and overall survival did not differ between the SRT and SHT arms.

Even with recent advances in RP and imaging technologies, such as choline positron emission tomography (PET)/CT and prostate-specific membrane antigen-based PET/CT, the results of this study contribute “significant clinical evidence regarding treatment of prostate cancer,” Dr Naito’s team stated. They explained that the newer PET/CT modalities have limitations in patients with PSA failure less than 1.0 ng/mL.

“Our results demonstrated that SRT may be feasible for patients with post-RP PSA failure even if we do not have a histological proof of local recurrence,” Dr Naito and colleagues wrote. “Administration of early SRT made it possible for some patients with treatment failure in our study to avoid SHT.”

Overall, the most common grade 3 to 4 adverse event was erectile dysfunction: 80% in the SHT group vs 74% in the SRT group. Administering SRT first may help some men avoid SHT and frequent adverse events such as gynecomastia and hot flushes.

Study limitations include the short follow-up periods and surrogate end point.

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Reference

Yokomizo A, Wakabayashi M, Satoh T, et al. Salvage radiotherapy versus hormone therapy for prostate-specific antigen failure after radical prostatectomy: A randomised, multicentre, open-label, phase 3 Trial (JCOG0401) [published online December 19, 2019]. Eur Urol. doi:10.1016/j.eururo.2019.11.023