Factors influencing the decision to add chemotherapy to adjuvant hormonal therapy in women with hormone receptor-positive breast cancer.
Authors: Chagpar AB , Lewis JL , McMasters KM , Edwards MJ 
Published: December 2010

Abstract #4105

Introduction: The decision to treat women with hormone receptor-positive breast cancer with chemotherapy in addition to hormonal therapy is complex. Models have been developed to assist physicians in estimating survival benefit associated with the addition of chemotherapy. How this information is used is unclear. The purpose of this study was to determine clinicopathologic factors influencing this decision, and the absolute improvement in 10-year overall survival for which clinicians will opt to add chemotherapy.&#x2028; Methods: The North American Fareston versus Tamoxifen Adjuvant (NAFTA) trial is an investigator-initiated multicenter trial in which hormone receptor-positive patients were randomized to receive either toremifene or tamoxifen adjuvant hormonal therapy. The decision to add adjuvant chemotherapy was left to the individual physician's discretion. Of the 1813 patients enrolled in the trial, 985 (54.3%) were younger than 70 years of age. A protocol violation occurred prior to initiating the trial in 43 patients (4.4%). These patients were excluded, and the remaining 942 patients formed the cohort of interest for this study. We evaluated the effect of clinicopathologic factors on the decision to pursue chemotherapy. In addition, for each patient, we calculated what the estimated 10-year overall survival would be if they received hormonal therapy alone, versus combined therapy with adjuvant chemotherapy (Adjuvant! Online, Version 8.0). The difference between these two values was calculated for each patient as the absolute survival benefit attributable to the addition of chemotherapy. We determined the absolute survival benefit attributable to chemotherapy at which clinicians opted to pursue chemotherapy in addition to hormonal therapy.&#x2028; Results: The median patient age in this cohort was 61 (range; 41-69), with a median tumor size of 1.2 cm (range; 0.1-14.0 cm). The majority of patients (n=929; 98.6%) were treated with hormonal therapy alone. Patients receiving chemotherapy tended to be younger (median 56 vs. 61 yrs, p=0.145), with larger tumors (median 2.0 vs. 1.2 cm, p&lt;0.001), of high grade (58.3% vs. 15.2%, p=0.002), with lymphovascular invasion (30.0% vs. 6.3%, p=0.024), and node positive disease (23.1% vs. 5.3%, p=0.031). Based on Adjuvant! Online estimates, patients who were treated with chemotherapy were projected to have a 1.4% absolute benefit in 10-year overall survival from the addition of chemotherapy; patients whom clinicians opted to treat with hormonal therapy alone were projected to have a 0.3% absolute benefit in 10-year overall survival if they would have been treated with the addition of chemotherapy (p&lt;0.001).&#x2028; Conclusion: Clinicians will opt to add adjuvant chemotherapy when the estimated absolute 10-year overall survival benefit of adding chemotherapy is 1.4%; whereas they will opt not to add chemotherapy when the absolute 10-year overall survival benefit of adding chemotherapy is 0.3%.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 4105.