PATTERNS OF DNA-PLOIDY AND S-PHASE FRACTION ASSOCIATED WITH BREAST-CANCER SURVIVAL IN BLACKS AND WHITES

A significant survival difference between black and white breast cance r patients has been observed in the United States, Evaluation of the p rognostic value of DNA ploidy and S-phase fraction (SPF) in black and white breast cancer patients may contribute to our understanding of th e mechanisms of racial disparity in survival, A sample of 98 patients (50 blacks and 48 whites) who participated in the Black/White Cancer S urvival Study was selected for DNA flow cytometry analysis, Patients w ere followed between 4.5 and 6.5 years, The impacts of DNA ploidy and SPF on breast cancer survival were examined, Kaplan-Meier survival cur ves, log rank statistics, and Cox proportional hazards regression were used for survival analyses, Black patients were more likely than whit e patients to have tumors with high SPF (P < 0.05), but there was no d ifference in DNA ploidy (P = 0.79), Because there were significant int eractions of both DNA ploidy and SPF with race, survival was examined separately for blacks and whites. Significantly poorer survival was ob served for white patients with class A ploidy (hypodiploidy, hypotetra ploidy, and hypertetraploidy; P = 0.001) and with high SPF (P = 0.025) , The elevated hazard ratios remained significant after adjusting for age and stage, Further adjustment for adjuvant therapy and histopathol ogical characteristics of tumor reduced the hazard ratios of SPF to a nonsignificant level, No significant associations were found between s urvival and DNA ploidy or SPF among blacks. DNA ploidy and SPF are pro gnostic factors for breast cancer survival in white patients but not i n blacks, This may have clinical implication in breast cancer manageme nt.