Parity as a prognostic factor in young breast cancer patients.

Data were analyzed concerning 219 female breast cancer patients less than 36 years of age who were diagnosed and treated in the Province of Saskatchewan, Canada, during 1946-72. Pathology slides were available for review on 171 of these patients, and invasive breast cancer could be confirmed in 136. Nulliparous patients had more favorable age-adjusted survival rates than parous patients for the total patient group and for those patients whose tumor was verified to be invasive cancer on pathologic review. Adjustment for potential confounding factors indicated that differences in survival among parity groups could be explained to a substantial degree by differences in distribution over node status and the nuclear grade of the primary tumor. Because these factors relate to the biologic behavior of breast cancer and because the distributions of these factors were significantly associated with the parity categories utilized in the analysis, the data provide some evidence that parity influences the behavior of breast cancer in young women.