Effect of Misclassified Underlying Cause of Death on Survival Estimates of Colon and Rectal Cancer

Abstract

Inaccurate coding of patients' Underlying Cause of Death (UCOD) has constrained cause-specific survival estimates for colon and rectal cancers. Using California data from the Accuracy of Cancer Mortality study, we compared the cancer site data from the California Cancer Registry (CCR) with UCODs reported on death certificates and reclassified the UCODs based on cancer registry data when they disagreed. We then calculated 1-, 3-, 5-, and 10-year cause-specific survival for colon and rectal cancers separately, before and after the reclassification. Records from 26 312 colon and 10 687 rectal cancer patients were examined. UCOD records disagreed with CCR records for 700 (6%) of 11 404 colon cancer deaths and with 1958 (39%) of 5011 rectal cancer deaths, and 82% of the misclassified rectal cancer deaths were coded as colon cancer deaths in the UCOD. Reclassification decreased cause-specific survival for both colon and rectal cancers, but the impact was more pronounced for rectal cancer (eg, 5-year cause-specific survival of colon cancer decreased by 2.8% and of rectal cancer decreased by 20.0% relative to previous estimates; absolute rates changed from 65.4% to 63.6%, and 81.2% to 64.9%, respectively, after reclassification). Interchangeable use of the terms colon cancer and colorectal cancer is likely to be one of the reasons for UCOD misclassification. Educational measures could improve the accuracy of UCOD for colon and rectal cancer deaths.

Increasing late stage colorectal cancer and rectal cancer mortality demonstrates the need for screening: a population based study in Ireland, 1994-2010

“…In 1981, Percy et al reported that misclassification led to over reporting of colon cancer deaths and underreporting of rectal cancer deaths [27]. More recently, in the US, Yin et al reported inaccurate coding of underlying cause of death, with the vast majority of misclassifications being colon cancers incorrectly classified as rectal cancers [28]. Further investigation is warranted to explore the extent and nature of misclassification on death certificates in European countries in recent years, perhaps comparing countries with rising and static rectal cancer mortality rates.…”

Colorectal Cancer Trends in California and the Need for Greater Screening of Hispanic Men

“…Misclassification has been reported for CRC as the underlying cause of death, although most of inaccuracies were due to death certificates assigning colon as the cause of death for rectal cancer patients, due to the interchangeable use of the terms colon and colorectal. 14 In addition, screening quality may differ between whites and Hispanics, which could attenuate the preventive effect of polyp removal. Despite these limitations, the size and diversity of the California population and the quality of CCR data are important factors in bringing to light the disparities uncovered in this study.…”

Population-level trends in relative survival for cervical cancer

“…12 Second, measuring cancer-specific survival is inherently difficult as data from death certificates is often inaccurate and may not reflect cancer-associated mortality in patients who die from complications and the sequelae of cancer. 13,14 …”