Phase II Trial Tests Benefit of Local Tumor Therapy

Scottsdale, Arizona—Systemic therapy is at the center of treatment for metastatic prostate cancer. Existing evidence has suggested that outcomes in men with advance disease may be improved with definitive treatment of the primary tumor (DTPT). Further, there is evidence that local therapy may alter disease biology as well as prevent symptomatic local progression.

Thus, according to researchers, definitive treatment of the primary tumor “may delay local and distant progression, prolong time to castration resistant prostate cancer (CRPC), and fatal metastatic burden.” Brian F. Chapin, MD, and colleagues reported on a phase II trial of DTPT during a poster session at the 94th Annual Meeting of the South Central Section of the American Urological Association. The poster was titled A Prospective, Multicenter, Randomized Phase II Trial of Best Systemic Therapy (BST) or BST plus Definitive Treatment (Surgery or Radiation) of the Primary Tumor in Metastatic Prostate Cancer.

The prospective, multicenter, randomized phase II trial was designed to test the hypothesis that DTPT added to BST will delay time to CRPC in men presenting with metastatic prostate cancer. A total of 120 men who have completed 6 months of BST, defined as any standard therapy for metastatic cancer, will be randomized in a 1:1 ratio to either continue BST or BST plus DTPT. Patients will be stratified by prostate-specific antigen (PSA) nadir at randomization (≤4 and >4) and by treatment center.

Patient and physician preference will determine the type of DTPT. Patients will be evaluated every 3 months with a history and physical exam and serum PSA. Progressive disease will be defined per Prostate Cancer Working Group 2 criteria, and a Bayesian design with interim monitoring will be implemented.

Following randomization of a minimum of 60 patients, the trial will be stopped if, at any time, the probability of one arm (A) is better than the other arm (B) is > 97.5%; at that time, A will be selected as superior. The final analysis will be conducted after patients have been followed for at least 24 months.

Eligibility criteria include prostate adenocarcinoma with documented evidence of metastatic disease per American Joint Committee on Cancer, Version 6 criteria. At randomization, patients must have castrate sensitive disease and not have received BST for >6 months prior. Exclusion criteria are small cell carcinoma, brain metastases, or CRPC within 6 months after initiation of BST.

A biomarker panel to predict benefit from DTPD will be identified using characterization of the prostate tumor and tumor microenvironment (stromal and immunologic components) and associated changes on magnetic resonance imaging.

Clinical trial information: NCT017514348

Source: Chapman BF, McGuire SE, Wang X, et al. A prospective, multicenter, randomized phase II trial of best systemic therapy (BST) or BST plus definitive treatment (surgery or radiation) of the primary tumor in metastatic prostate cancer. Abstract of a poster presented at the 94th Annual Meeting of the South Central Section of the American Urological Association, October 29, 2015, Scottsdale, Arizona.