Scientists at Oregon Health & Science University Cancer Institute and five other institutions have found a more accurate way to report and predict the survival of colon cancer patients by calculating a statistic called conditional survival. Conditional survival takes into account the time already survived since diagnosis.
Patients usually receive an estimate of their survival probability only when their disease is initially diagnosed. But after a patient has remained disease-free one year or more later, his or her prognosis may change, and often improves.
The results of the study will be presented on Monday, June 5 at the 2006 annual meeting of the American Society of Clinical Oncology in Atlanta, Ga. The presentation is one of eight abstracts authored by members of OHSU's Department of Radiation Medicine to be accepted for presentation at the conference.
Led by Samuel J. Wang, M.D., Ph.D., Holman Research Pathway resident at OHSU, in collaboration with Charles R. Thomas, Jr., M.D., professor and chair of the Department of Radiation Medicine, and seven other scientists, the study analyzed 5,587 colon cancer research subjects who were enrolled in four National Surgical Adjuvant Breast & Bowel Project (NSABP) trials to determine their five-year conditional survival rates.
Subjects in the study had already survived without disease recurrence for up to five years after diagnosis. The results were sorted by number of years since diagnosis, age, sex, race, stage of disease, location of tumors and other factors.
The results showed that as more time elapsed since diagnosis, most subjects experienced an improvement in their subsequent five-year conditional survival following the initial disease-free period. For instance, at the time of diagnosis, patients had a 76 percent probability of surviving five years, but those who had already survived disease-free for five years had a 90 percent chance of surviving an additional five years.
"This study confirms that a patient's prognosis usually improves as he or she survives disease-free for longer periods of time from initial diagnosis," Wang said. "These new conditional survival tables will allow physicians to give patients more accurate survival estimates after they have already survived a period of time since their diagnosis and treatment."
Other participating institutions were the University of Texas Health Science Center at San Antonio; the University of Pittsburgh; the University of Chicago; the AMC Cancer Research Center in Denver; and Allegheny General Hospital in Pittsburgh.
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