Primary tumor and patient characteristics in breast cancer as predictors of adjuvant chemotherapy regimen: A regression model

e11632 Background: Adjuvant chemotherapy is used to reduce the risk of recurrence of breast cancer. This study was undertaken to determine which patient and tumor characteristics are important in guiding the choice of adjuvant chemotherapy. Methods: A retrospective review was undertaken of patients diagnosed with breast cancer (stages I-III) at a regional cancer center from 2004–7. Patient and tumor characteristics were identified and chemotherapy regimens compared. Binary logistic regression analysis was performed to the choice of FEC/D, CEF, AC/T, or ddAC/T against AC or CMF, or the choice of chemotherapy to hormonal therapy only. Univariate analysis was used to select factors (p<0.1) for entry into a multivariate stepwise logistic regression model using the forward method. Odds ratios with 95% CI were calculated. A p-value of < 0.05 was significant and comparisons were two tailed. Results: Model 1 (n=871) included regimen (AC or CMF vs. aggressive regimen) as the dependant variable. Indicators of choice of aggressive regimen were higher stage [OR 4.7 (CI 3.3, 6.8)], positive nodes [2.5 (1.6, 3.8)], negative PR [2.1 (1.4, 3.1)], higher grade [1.4 (1.0, 1.8)], and age [0.91 (0.88, 0.92)]. Model 2 (n=640) involved choice of any regimen (chemotherapy vs. hormonal therapy only) as the dependant variable. Indicators of choice of chemotherapy were higher stage [7.19 (2.8, 18.4)], higher grade [7.02 (3.3, 14.8)], positive nodes [3.25 (0.98, 10.77)], age [0.85 (0.81, 0.90)], and ER negativity [0.04 (0.004, 0.37)]. Factors not significant in both models were: family history, comorbidities (renal/hepatic dysfunction, diabetes, cardiac history, or neuropathy), treating medical oncologist, histology, Her2/neu, > 3 positive nodes, ratio of positive to total nodes, multicentricity, multifocality, and positive margin status. Conclusions: This study verifies known important factors for choice of chemotherapy regimen as found in current guidelines, quantifies their effects at our center, and excludes others thought to be important. Further studies are required to confirm these results both nationally and internationally, where risk stratification may be different, and if variables predicting adjuvant radiation therapy are similar. No significant financial relationships to disclose.