Breast cancers in U.S. residing Indian-Pakistani versus non-Hispanic White women: comparative analysis of clinical-pathologic features, treatment, and survival.

South Asians from India and Pakistan represent one of the fastest growing immigrant populations in the US, yet there are limited data assessing breast cancers for this distinct ethnic sub-group. The aim of this study was to analyze clinical-pathologic, treatment and outcome characteristics of U.S.-residing Indian-Pakistani (IP) versus non-Hispanic white (NHW) female breast cancer patients to assess if any differences/disparities exist. The study cohort consisted of 2,393 IP and 555,832 NHW women (diagnosed 1988-2006) in the SEER database. Differences between the two populations were analyzed using chi-squared and multivariate regression analysis. Age-adjusted incidence, mortality, and relative survival rates were calculated for the two groups. Significant differences in the characteristics of the IP cohort's invasive disease included: younger median age at presentation; larger tumor size; higher stage, higher grade, more involved lymph-nodes, and more hormone receptor negative disease (all P < 0.01). The age-adjusted incidence and breast cancer mortality were lower in IP women. The relative survival at 5 years was statistically significant at 84% for IP versus 89% for NHW women, but was not significantly different on multivariate analysis (P > 0.05). Within each stage (Tis, I, II), there were no disparities in the rate of breast conservation surgery (BCS) or in the percentage of patients receiving adjuvant radiation after BCS for the 2 cohorts. Post-mastectomy radiation was delivered significantly more often in stage I/II IP patients undergoing mastectomy. In conclusion, this analysis suggests that while there appear to be significant differences in the features of breast cancers of US-residing IP women, no disparities were noted in the rates of breast conserving surgery or adjuvant radiation, as seen in some other ethnicities. The more aggressive clinical-pathologic features stage-for-stage in IP women may partially explain the more frequent use of post-mastectomy RT in this patient population. These findings warrant further investigation.