Adjuvant Docetaxel May Adversely Affect Progression of High-Risk Prostate Cancer: Presented at ASCO-GU

By Matt Silver

SAN FRANCISCO -- February 12, 2018 -- Adjuvant docetaxel without hormonal therapy or continuous corticosteroids may adversely affect the biochemical progression of prostate cancer in patients who have low or undetectable prostate-specific antigen (PSA) levels after surgery, according to results of an open-label, phase 3 study presented here on February 8 at the 2018 Genitourinary Cancers Symposium.

Although adjuvant chemotherapy is standard treatment for other solid tumours, it has not yet been proven to be effective in treating prostate cancer. In an effort to understand the utility of adjuvant docetaxel in patients with high-risk prostate cancer, Goran M. Ahlgren, MD, PhD, Scandinavian Prostate Cancer GROUP, Lund University, Malmoe, Sweden, and colleagues randomised 459 patients who had undergone prostatectomy to receive either 6 cycles of adjuvant docetaxel 75 mg/m2 every 3 weeks without daily prednisone or surveillance alone until the endpoint (PSA progression ≥ 0.5 ng/ml) was reached.

In all, 109 of 459 patients (41.4%) reached the primary endpoint: 103 of 230 (44.8%) patients in the docetaxel group and 87 (38.0%) of 229 patients in the surveillance group.

Kaplan-Myer analysis found no evidence of non-proportional hazards over time, but upon exclusion of the 76 patients with PSA > 0.2 after surgery, the analysis outcome demonstrated proportional hazards and favoured surveillance (P = .02). Surveillance remained the favoured treatment in a Cox multivariate analysis (P = 0.03).

The median time to progression, death, or last follow up was 56.8 months.

“The outcome was completely opposite [of what was expected] in patients with measurable PSA compared with patients with low [PSA] values,” Dr. Ahlgren said. “This raises the hypothesis that the proliferation of PSA-producing tumour cells may accelerate after docetaxel treatment.”

Limitations of this study include the fact that not all patients received docetaxel by protocol, some patients received radiation treatment before the endpoint, and there was a lack of stratification for PSA after surgery.

The 2018 Genitourinary Cancers Symposium is cosponsored by the American Society of Clinical Oncology (ASCO), the American Society for Radiation Oncology (ASTRO), and the Society of Urologic Oncology (SUO).

[Presentation title: Adverse Effect of Docetaxel Versus Surveillance After Radical Prostatectomy for High Randomized, Open-Label Phase III SPCG 12 Trial. Abstract 30]

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