Static disease on anastrozole provides similar benefit as objective response in patients with advanced breast cancer

Background. This paper reports on the clinical relevance of durable static disease (SD) (≥ 24 weeks) in breast cancer patients treated with the aromatase inhibitor anastrozole. Patients and methods. All patients were part of two prospective, randomised, multicentre studies in postmenopausal women with advanced disease in which megestrol acetate was compared with anastrozole 1 mg. Survival from initiation of treatment was analysed by the response type, i.e., complete response (CR)/partial response (PR), static disease (SD) (≥ 24 weeks), or progressive disease (PD), achieved on therapy. Results. Median survival with anastrozole 1 mg was similar between patients who obtained CR/PR and SD (≥ 24 weeks). Similarly, no difference in survival was observed in patients treated with megestrol acetate who achieved CR/PR and SD. With both treatments patients with CR/PR and SD had improved survival over those patients with PD within 24 weeks. There was no difference between treatment arms for patients showing PD within 24 weeks. Conclusions. These data confirm that durable SD (≥ 24 weeks) is a clinically useful remission criterion in postmenopausal women with advanced breast cancer with predictive value for overall survival. It also confirms the value of this endpoint with anastrozole, a new generation aromatase inhibitor.