Sequence of radiotherapy with tamoxifen in conservatively managed breast cancer does not affect local relapse rates

Purpose To evaluate whether the sequencing of tamoxifen (TAM) relative to radiation (RT) affects outcome in breast cancer patients treated with conservative surgery (CS) plus RT (lumpectomy with RT). Methods Between 1976 and 1999, 1,649 patients with stage I or 11 breast cancer were treated with CS plus RT at Yale-New Haven Hospital (New Haven, CT). TAM was administered to 500 patients. The timing of TAM relative to RT was documented for each patient. Of the 500 patients, the timing of TAM was unclear in five patients, was administered concurrently with RT in 254 patients (CON-TAM), and was administered sequentially after completion of RT in 241 patients (SEQ-TAM). Results There were no differences between the CON-TAM and SEQ-TAM group in T stage, estrogen and progesterone status, nodal status, histology, or margin status. The CON-TAM group was slightly older than the SEQ-TAM group (62 v 58 years) and received chemotherapy in addition to TAM less frequently (14% v 38%). As of September 2002, with a median follow-up of 10.0 years, there were no significant differences between the CON-TAM and SEQ-TAM groups in overall survival (84% v 82%; hazard ratio [HR], 1.234; 95% CI, 0.42 to 2.05; P = .45), distant-metastasis-free rate (82% v 78%; HR, 1.55; 95% CI, 0.89 to 2.68; P = .12), ipsilateral breast-relapse-free rate (90% v 86%; HR, 0.932; 95% CI, 0.42 to 2.05; P = .86), or contralateral breast-relapse-free rate (95% v 93%; HR, 0.892-1 95% CI, 0.53 to 1.48; P = .66). Conclusion Although the concurrent use of TAM with RT may theoretically render cancer cells less responsive to RT, this retrospective study suggests that in practical application, concurrent administration of TAM with RT does not compromise local control.