Colorectal cancer: Incidence and mortality among the Medicare population (1990--1997)

Background. Population-based studies of colorectal cancer incidence and mortality of Medicare beneficiaries 65 and older are limited. The Surveillance, Epidemiology and End Results data provided estimates based on 12% of the U.S. population. A few studies addressed 30-day post operative mortality. The results of these studies are conflicting.;Methods. 100% of Medicare beneficiaries 65 years or older with a first known diagnosis of colorectal cancer from 1990--1997 were studied. We utilized a cross-sectional study design to study incidence and mortality rates and a longitudinal study design to examine 30-day survival rates. Tumor site was divided into rectum, distal colon and proximal colon. The analysis was stratified by age-group, race, sex, presence or absence of metastatic disease and site of origin.;Results. The incidence rates for colon cancer were 193.77 patients' age 65--69 years in 1990--1991 and 184.17/100,000 in 1996--1997. The incidence rates for colon cancer patients 85 years and older were 349.89 and 458.43/100,000 in 1990--1991 and 1996--1997. Right-sided colon cancer incidence rates were 141.65 and 170.04/100,000 and left-sided colon cancer rates were 123.98 and 120.84 in 1990--1991 and 1996--1997. The rectal cancer incidence rates were much lower than colon cancer incidence rates. The incidence trend with age persisted with all three sites of colorectal cancer. Age-adjusted incidence rates for colon cancer were 306.66 and 325.90 and for rectal cancer were 38.03 and 41.11 per 100,000 in 1990--1991 and 1996--1997. Left-side colon cancer patients had the highest 30-day post operative mortality (7.68/100 in 1990--1991 and 8.73/100 in 1996--1997) among the three sites of the tumors.;Conclusions. The study populations are getting older. More colon cancer as opposed to rectum cancer cases were found in blacks, women and younger patients. Colorectal cancer incidence rates increased during 1990--1997 but there was a decreased trend of left-side colon cancer. There is a substantial variation in colorectal cancer incidence among states. 30-day mortality rates of colon cancer increased and rectal cancer decreased during the study period.