Risk of Ipsilateral breast tumor recurrence in patients treated with Tamoxifen or Anastrozole following breast-conserving surgery with or without radiotherapy.

Background: It is unknown whether anastrozole (Ana) is superior to tamoxifen (Tam) with regard to local control after breast-conserving surgery without radiotherapy (RT).

Patients And Methods: Two hundred and ninety-two breast cancer patients who had undergone breast-conserving surgery and been treated with Tam or Ana, with or without RT, were retrospectively analyzed. Ipsilateral breast tumor recurrence (IBTR)-free survival rates were compared according to the treatment drug and RT.

Results: In the Tam group, IBTR-free survival rates did not significantly differ according to the use or absence of RT (p=0.08), whereas in the Ana group, a significant difference (5-year IBTR-free survival rate, 98.8% in the RT group vs. 65.7% in the no RT group, p<0.0001) was found. In addition, multivariate analysis showed that RT use was an independent prognostic factor for IBTR-free survival (p=0.01) among the patients treated with Ana.

Conclusion: Caution is needed when RT is omitted for patients undergoing breast-conserving surgery and receiving Ana for adjuvant treatment.