A reliable method of assessing a cancer patient's response to treatment is important. It shows doctors whether the prescribed therapy is working and allows them to quickly and confidently change the treatment plan when it's ineffective---and presumably improve the patient's quality of life as a result.
The U-M researchers studied 62 men with advanced prostate cancer and found that those whose PSA level declined 50 percent or more after eight weeks of chemotherapy had a significantly higher survival rate.
PSA screening tests are used to measure the level of a prostate-specific antigen in the blood---which indicates the presence of prostate cancer. They also have been used to gauge patients' response to cancer therapy, but that application has been controversial because opinions differ on its validity and precisely how to interpret test results.
The U-M researchers found that patients whose PSA levels declined at least 50 percent after eight weeks of chemotherapy survived for 91 weeks (median), compared with 38 weeks for those whose PSA level did not decline 50 percent.
The study is detailed in the May issue of the Journal of Clinical Oncology. It was conducted by David C. Smith, M.D.; Kenneth J. Pienta, M.D.; Rodney L. Dunn, M.S.; and Myla S. Strawderman, M.S.