SOLE cycle.

Last week we discussed surprisingly high rates of distant relapse at 20 years in women with hormone-receptor positive breast cancer, particularly in those with node positive disease. One school of thought is that these patients may benefit from extended adjuvant endocrine therapy (i.e., at least 10 versus 5 years). In a new twist, this month’s SOLE trial explored the potential benefit of doing intermittent extended endocrine therapy. Preclinical studies indicate cells that become resistant to estrogen blockade die when re-exposed to estrogen...so intermittent cessation may actually add efficacy. After an initial 5 years of endocrine therapy, patients were randomized either to continue 5 more years as usual or to receive 9 month cycles with 3 month breaks. This latter intermittent approach failed to improve the primary endpoint of disease-free survival. What else didn’t it improve? Side effects. This is important considering some people may use this data to support treatment breaks for patients with burdensome symptoms since disease control was basically the same for each arm. What the study did do is raise issues regarding the complexity of defining post-menopausal status in these women--and leave us spinning our wheels when it comes to optimizing and individualizing endocrine therapy.