VALIDITY OF SELF-REPORTED CANCERS IN A PROSPECTIVE COHORT STUDY IN COMPARISON WITH DATA FROM STATE CANCER REGISTRIES

The accuracy of self-reported cancer diagnoses in a prospective study was compared with population-based cancer registry data in four states . The study cohort included 65,582 men and women aged 39-96 years who were participants in the Cancer Prevention Study II Nutrition Survey, begun by the American Cancer Society in 1992, Estimates of sensitivity (the proportion of study participants with a registry-documented canc er who self-reported the cancer) ranged from 0.79 for an exact match o f cancer site and year of diagnosis (+/-1 year) to 0.93 for a match of any reported cancer. The sensitivity of exact matches varied consider ably by cancer site and was highest for breast, prostate, and lung can cers (0.91, 0.90, and 0.90, respectively) and lowest for rectal cancer and melanoma (0.16 and 0.53, respectively). Sensitivity also varied s lightly by the age, education, and smoking status of study participant s. Estimates of sensitivity were virtually identical for each of the f our states. The positive predictive value (the proportion of self-repo rted cancers that were confirmed by the registries) was 0.75 overall a nd also varied by cancer site, Unlike sensitivity, however, this propo rtion varied considerably by state. AII serf-reports of cancer that we re not confirmed by the registries were further investigated by repeat questionnaires and acquisition of medical records. Low positive predi ctive Values were due to underascertainment of true cancer cases by th e registries, inaccurate reporting on the part of study participants, and problems with the algorithm used by the state to link the study po pulation to the registry data. In conclusion, the ability of members o f this cohort: to report a past diagnosis of cancer accurately is quit e high, especially for cancers of the breast, prostate, lung, and colo n, or for the occurrence of any cancer.