Multiple primary cancers: relative risk in New Mexico's triethnic population

A review of the population-based New Mexico Tumor Registry data identified 446 patients with nonsimultaneous multiple primary cancers, excluding non-melanoma skin cancers and carcinomas in situ of the uterine cervix. Expected numbers of cases were established by observing the person-years of exposure to the risk of developing a second or subsequent primary cancer and then applying the appropriate locally determined age-, sex-, ethnic-, and site-specific cancer incidence rates. The relative risk (observed/expected) of developing a second primary cancer was elevated for "Anglo" and Spanish American cancer patients in comparison with the risk of developing a first primary cancer in persons who have never had one. Only six cases of nonsimultaneous multiple primary cancer were observed (6.39 expected) in the region's American Indian population. There were differences in site-site associations among the three ethnic groups, but in many categories there were too few cases for analysis.