CHICAGO--Johnson & Johnson's prostate cancer drug Zytiga showed a slightly improved survival benefit in updated data from a late-stage study that also revealed the potential for a new way to measure the common disease.
The data, presented at the annual meeting of the American Society of Clinical Oncology, reveal that measuring circulating tumor cells--cancer cells that have fallen off a tumor into the bloodstream--correlates with patient survival. The measuring of such cells could effect the development of future medicines because it may be used instead of measuring overall patient survival in a clinical trial, making such studies shorter, smaller and cheaper.
In the study, the median overall survival of patient on Zytiga rose to 4.6 months, compared to the previously reported benefit of 3.9 months. The measurement came after 20.2 months on treatment, showing that patients on the drug lived for 15.8 months compared to 11.2 months on a placebo.
Zytiga targets a protein that plays an important role in the production of testosterone, which stimulates cancer cells to continue growing.
The drug received Food and Drug Administration approval in April in combination with prednisone for patients with a certain type of late-stage prostate cancer previously treated with chemotherapy. The drug was given a shorten review and the decision came ahead of its June 20 regulatory goal date.
Prostate cancer is very common in older men, who are screened with a test for prostate-specific antigen, or PSA. But that measure can be deceiving, sometimes rising even when a patient is benefiting from a treatment, and vice versa, according to Howard Scher, chief of the Genitourinary Oncology Service at Memorial Sloan-Kettering Cancer Center in New York.
The Zytiga trial found that measuring the circulating cells predicted a better prognosis and improved survival as early as four weeks after taking the drug. The measurement of the cells in relation to patient survival was part of a formal collaboration with the FDA. The cells represent about one cell in a billion in the blood stream, according Dr. Scher.
While the data are encouraging, Dr. Scher said the finding will be tested in subsequent studies that may eventually determine if the measure could help guide treatment decisions for individual patients.‹
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