With long-term follow-up, letrozole can be safely administered concomitantly with adjuvant breast radiotherapy (RT) in postmenopausal patients with stage 1 to 2 breast cancer, a study published online ahead of print in the journal Annals of Oncology has shown.1

For the phase 2 study, researchers enrolled 150 postmenopausal women with stage 1 to 2 breast cancer and randomly assigned them to receive letrozole concurrently or sequentially to adjuvant radiotherapy. Researchers also conducted sub-studies to identify patients at risk for developing radiation-induced subcutaneous fibrosis.

Results showed that at a median follow-up of 74 months, 5 patients developed grade 2 or higher radiation-induced subcutaneous fibrosis, but there were no significant differences between the 2 treatment arms. Researchers observed no grade 2 or higher lung or symptomatic cardiac toxicities.


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For the sub-studies, the median radiation-induced lymphocyte apoptosis value of the patients who had developed grade 2 or higher radiation-induced subcutaneous fibrosis was 6.9% compared with 13% among those who developed grade 1 or lower radiation-induced subcutaneous fibrosis (P=.02).

The study also identified 2 single nucleotide polymorphisms associated with radiation-induced lymphocyte apoptosis, which are both located on the PHACTR3 gene on chromosome 20q13.33.

“Translational sub-studies showed that high [radiation-induced lymphocyte apoptosis] values were correlated with patients who did not develop [radiation-induced subcutaneous fibrosis],” the investigators conclude.

REFERENCE

1. Bourgier C, Kerns S, Gourgou S, et al. Concurrent or sequential letrozole with adjuvant breast radiotherapy: Final results of the CO-HO-RT phase II randomized trial [published online ahead of print December 17, 2015]. Ann Oncol. doi:10.1093/annonc/mdv602.