Flutamide With or Without PROSTVAC in Non-metastatic Castration Resistant (M0) Prostate Cancer

Area of Science:

• Oncology
• Immunology
• Prostate Cancer Research

Background:

• Prior to 2018, non-metastatic castration-resistant prostate cancer (nmCRPC) lacked a standard treatment protocol.
• Androgen receptor antagonists (ARAs) were often administered sequentially for nmCRPC management.

Purpose of the Study:

• To evaluate the efficacy of combining the androgen receptor antagonist flutamide with PROSTVAC, a pox viral vaccine targeting prostate-specific antigen (PSA).
• To compare treatment outcomes in patients with nmCRPC receiving flutamide alone versus flutamide plus PROSTVAC.

Main Methods:

• A multicenter, randomized clinical trial was conducted.
• Patients with non-metastatic prostate cancer and rising PSA on androgen deprivation therapy were randomized.
• Treatment arms included flutamide alone and flutamide plus PROSTVAC, with evaluation of antigen-specific immune responses.

Main Results:

• No significant difference in median time to treatment failure was observed between the flutamide alone arm (4.5 months) and the flutamide+PROSTVAC arm (6.9 months; P = .38).
• PSA response rates (>50% reduction) were similar in both groups (7 patients each).
• Antigen-specific immune responses were comparable between arms, and treatments were generally well-tolerated, with injection site reactions being the most common side effect in the vaccine group.

Conclusions:

• The combination of flutamide and PROSTVAC did not demonstrate improved outcomes for men with nmCRPC compared to flutamide monotherapy.
• The study suggests that this specific vaccine combination does not offer a clinical benefit in this patient population.