VANCOUVER, B.C. – Men live longer when a “watchful waiting” prostate cancer strategy is followed by treatment later in the course of the disease, compared with aggressive initial treatment, Dr. Li Li said at the annual meeting of the North American Primary Care Research Group.
Dr. Li and his associates from Case Western Reserve University, Cleveland, conducted a survival analysis using 1991-2001 Medicare-Surveillance, Epidemiology, and End Results (SEER) linked data, reviewing the disease course of 138,670 men diagnosed with prostate cancer. A follow-up analysis was performed in 2004. Survival was analyzed based on whether patients were followed by various cancer management strategies, including:
▸ Watchful waiting, in which patients received no initial treatment, but follow-up examinations after their diagnosis.
▸ Watchful waiting with delayed treatment, in which active hormone treatments were instituted during some follow-up point based on disease course.
▸ No treatment, in which patients did not receive any subsequent examinations or active treatments after the initial cancer diagnosis.
Overall survival and prostate-cancer specific survival rates were adjusted for age, ethnicity, comorbidity, screening, socioeconomic status, and cancer stage/grade.
Opting for no treatment or follow-up was associated with a “huge, almost fourfold increase in dying,” even among men who were older than 80 years, in all likelihood because the strategy prevented identification and treatment of competing causes of mortality, said Dr. Li.
However, even prostate-specific survival was strongly adversely affected by a lack of treatment or follow-up in men of all ages.
Watchful waiting with no subsequent treatment led to nearly 25% higher overall mortality than did aggressive treatment for men who were younger than 80 years, with a hazard ratio of 1.24 (1.19-1.28), whereas the strategy did not significantly increase mortality over aggressive treatment in older men (hazard ratio 1.04 (0.99-1.09).
Watchful waiting followed by treatment if necessary conferred a survival benefit regardless of mens' ages at diagnosis, said Dr. Li during an oral presentation at the meeting.
Men followed by watchful waiting who did eventually receive treatment for prostate cancer had lower all-cause mortality than any other strategy: watchful waiting without treatment, hormone therapy only, or no treatment or follow-up.
In men under age 80, the relative risk for survival with this strategy was 0.88 (0.85-0.92); in men 80 and older, it was 0.72 (0.68-0.77), representing a 12% and 28% survival advantage, respectively.
When Dr. Li and his associates studied the 64% of men in the cohort who had low to intermediate risk prostate cancer, age became a factor as a strategic consideration.
In this group, watchful waiting without subsequent treatment led to slightly lower overall survival rates than did aggressive treatment in men over age 80, with a relative risk of 1.13 (1.06-1.22). The survival difference was greater for men aged 80 or younger, with a relative risk of 1.28 (1.22-1.33).
In both age groups of men at low to intermediate risk, watchful waiting followed by treatment led to higher survival rates than any other strategy. Prostate cancer-specific survival was highest in low to intermediate-risk men who were followed by watchful waiting without subsequent treatment.
Among the oldest men (over age 80) in this risk group, watchful waiting with delayed treatment prolonged disease-specific survival at about the same rates as aggressive treatment.
However, men under age 80 had diminished prostate-specific survival rates of nearly 40% when their treatment was delayed compared with initial aggressive treatment.