Extended intermittent letrozole not better than continuous use in SOLE study, but temporary treatment breaks may be safe for some patients

Study investigator Dr Marco Colleoni, Director, Division of Medical Senology at the European Institute of Oncology, Milan, Italy, member of the International Breast Cancer Study Group (IBCSG) and of the BIG Executive Board, says:
“These results did not support our main hypothesis, but they do support the safety of temporary treatment breaks, which would mean a lot for patients’ quality of life, and contribute to the further tailoring endocrine treatment.”
Study details
SOLE is the first trial evaluating a de-escalation of extended adjuvant endocrine therapy. From December 2007 to October 2012, it enrolled 4,851 postmenopausal women with hormone receptor-positive breast cancer who were cancer-free after surgery and had already completed 4 to 6 years of adjuvant endocrine therapy. 2,426 received extended continuous letrozole, and 2,425 patients intermittent letrozole that involved several treatment breaks. Scientists compared the disease-free survival rate (DFS, i.e. absence of cancer cells in the body) in the two groups after five years, and observed that DFS was 87.5% in the continuous letrozole group and 85.8% in the intermittent letrozole one.
22 countries involved
240 sites from 22 countries worldwide were involved in this trial, which was led by the International Breast Cancer Study Group (IBCSG) under the Breast International Group (BIG) umbrella and in collaboration with Novartis.