Abstract PR08: Chemotherapy modification by race in early breast cancer treatment

Abstract

Abstract Introduction: African American (AA) women are less likely to receive recommended standard treatment or discontinue treatment early for their breast cancer in comparison to white women. Dose reductions and delays during breast cancer chemotherapy can negatively affect survival. The purpose of this study was to examine racial differences in chemotherapy dose modifications among early stage breast cancer patients. We also explored the role of neutropenia in explaining these differences. Methods: Patients were selected from the Breast Cancer Treatment Disparity Study that is composed of AA and white women from New Jersey who were diagnosed with stage I, II, and T3N1M0 breast cancer between 2005-2010, with no prior history of cancer, and age ≤ 85 years. Patients who received chemotherapy as part of their breast cancer treatment were included. Detailed data on chemotherapy administration was abstracted from patient medical records. Chemotherapy dose delivered was measured using relative dose intensity (RDI), defined as the amount of drug delivered per unit time expressed as a fraction of expected dose intensity of a standard regimen. The National Cancer Comprehensive Network Guidelines were used for reference (expected) values of chemotherapy dose and schedule. RDI captures modifications resulting from both delays in administration or reduction in dose and it was computed for the entire course of therapy as well as for each cycle delivered. Racial differences in the mean RDI delivered (per subject and per cycle) and risk of >15% reduction in RDI (per subject) were examined using repeated measures linear and binomial regression models, respectively. The models were adjusted for white blood cell (WBC) level during chemotherapy. Results: The study included 143 AA and 145 white patients (with a total of 2063 chemotherapy cycles). The majority of patients received adjuvant chemotherapy (white= 93.1%, AA= 91.6%) and the remaining received neoadjuvant chemotherapy (white= 6.9%, AA= 8.4%) with no differences by race. Commonly administered regimens were dose-dense doxorubicin/cyclophosphamide followed by paclitaxel every two weeks (AA= 25.2%, white= 32.4%), docetaxel/cyclophosphamide every three weeks (AA= 23.1%, white= 17.2%), doxorubicin/cyclophosphamide every three weeks (AA= 11.9%, white= 12.4%), and doxorubicin/cyclophosphamide followed by weekly paclitaxel (AA= 9.8%, white= 13.1%). Receipt of anthracycline-based regimen was similar between AAs and whites (67.1% and 69.7%, respectively), as was addition of taxanes to anthracycline-based regimen (AA= 82.3%, white= 80.2%). A higher proportion of AA patients (10.5%) did not complete the recommended number of cycles in comparison to whites (5.5%), though the difference was not statistically significant (p= 0.120). Mean RDI per subject was 94.4% for AAs and 100.0% for whites (difference= −5.62%, p= 0.005). After adjusting for WBC level during chemotherapy, the mean RDI difference was −5.29% (p= 0.009). When RDI per cycle was examined, the mean unadjusted and adjusted RDI difference between AAs and whites were −8.27% (p< 0.001) and −7.92% (p< 0.001), respectively. The proportion of patients with >15% reduction in RDI was more than twice among AAs than whites (21.7% versus 8.3%, p=0.001). The unadjusted risk of >15% reduction in RDI was 2.62 (95% CI: 1.40, 4.89) in AA women as compared to white women; and was 2.50 (95% CI: 1.33, 4.70) after adjusting for WBC level. Conclusions: We found that AA breast cancer patients were significantly more likely to receive a reduced dose of chemotherapy as compared to white patients. WBC levels during the course of chemotherapy did not explain the racial disparity in chemotherapy dose reduction. The reasons for dose reduction in AA breast cancer patients merit investigation. This abstract was also presented as Poster A91. Citation Format: Sheenu A. Chandwani, Kim M. Hirshfield, Adana A. Llanos, Elisa V. Bandera, Yong Lin, George G. Rhoads, Kitaw Demissie. Chemotherapy modification by race in early breast cancer treatment. [abstract]. In: Proceedings of the Seventh AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 9-12, 2014; San Antonio, TX. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2015;24(10 Suppl):Abstract nr PR08.