Continuous vs intermittent extended adjuvant letrozole for b
Intermittent or continuous extended adjuvant endocrine therapy led to virtually identical long-term survival in hormone receptor (HR)-positive breast cancer, according to an updated analysis of a randomized trial.

This phase 3 randomized, open-label Study of Letrozole Extension (SOLE) studied the effect of extended intermittent letrozole treatment in comparison with continuous letrozole. In parallel, the SOLE estrogen sub-study (SOLE-EST) analyzed the level of estrogen during the interruption of treatment.

SOLE enrolled 4884 postmenopausal women with hormone receptor-positive, lymph node-positive, operable breast cancer, and among them, 104 patients were enrolled in SOLE-EST. They must have undergone local treatment and have completed 4-6 years of adjuvant endocrine therapy. Patients were randomized between continuous letrozole and intermittent letrozole treatment.

- After a median follow-up of 84 months, 7-year disease-free survival was 81.4% in the intermittent group and 81.5% in the continuous group.

- Reported adverse events were similar in both groups. Circulating estrogen recovery was demonstrated within 6 weeks after the stop of letrozole treatment.

Extended adjuvant endocrine therapy by intermittent administration of letrozole did not improve disease-free survival compared to continuous use despite the recovery of circulating estrogen levels. The similar disease-free survival coupled with previously reported quality-of-life advantages suggests intermittent extended treatment is a valid option for patients who require or prefer a treatment interruption.

Annals of Oncology