Erlotinib Has Moderate Single-agent Activity In Chemotherapy-naïve Castration-resistant Prostate Cancer: Final Results Of A Phase II Trial

Main Category: Prostate / Prostate Cancer
Also Included In: Urology / Nephrology;  Cancer / Oncology
Article Date: 02 Nov 2009 - 1:00 PDT

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UroToday.com - This was an open label single institution study that looked at the activity and toxicity of single agent erlotinib in patients with CRPC who have not received chemotherapy yet. The mechanisms by which prostate cancer becomes castration resistant are variable and multiple. One hypothesis is that the overexpression of the epidermal growth factor receptor (EGFR) allows for downstream cell signaling causing cancer cell growth and proliferation. Erlotinib is an oral inhibitor of EGFR with acceptable toxicity profile and with approved indications in metastatic lung and pancreatic cancers. Accordingly, this study took place.

Given the uncertainly as to whether PSA is the accurate surrogate for responses in such novel targeted agents, it was not used to implicate disease progression; rather imaging studies were used to decide progression along with changes in PSA-doubling time (PSA-DT). The primary end point was to estimate the overall clinical benefit of erlotinib in this setting. Patients received erlotinib at 150 mg daily until progression, investigator's discretion, severe toxicity, or withdrawal.

Twenty-nine patients were enrolled and the estimated clinical benefit was 31% including 2 patients who showed a partial response and 5 patients with stable disease. Importantly, the PSA-DT improved in all responding patients. Furthermore, the 1 and 2 year overall survival of 58% and 27% appears favorable even when compared with chemotherapy. In addition, patients who were on this study were still able to receive chemotherapy once progression was documented. The side effects were as expected including fatigue, rash, and diarrhea. These adverse events were all manageable and only two patients required dose modifications.

Our trial suggests the activity of erlotinib as monotherapy in this setting, and argues in favor of exploring this agent further in combination with other active therapies in CRPC.

Written by Chadi Nabhan, MD, FACP as part of Beyond the Abstract on UroToday.com

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