An Analysis of Serum Interleukin-6 Levels to Predict Benefits of Medroxyprogesterone Acetate in Advanced or Recurrent Breast Cancer

Abstract

Treatment of advanced or recurrent breast cancer with medroxyprogesterone acetate (MPA) shows high response rates and the accessory effects of appetite stimulation, improvement in performance status (PS) and bone marrow protection. In recent years, interleukin-6 (IL-6) has been reported to cause cachexia. In this study, to clarify the significance of IL-6 in advanced or recurrent breast cancer, the relationship between the IL-6 level and clinical findings or effect of MPA was investigated. Sixty-five patients with recurrent or advanced breast cancer participated in a prospective study. The age of patients ranged from 28 to 79 years with an average age of 51.3 years. IL-6 level was investigated in these patients dosed with 800 mg/day of MPA and in 17 postoperative nonrecurrent patients. Serum MPA level was measured by high-performance liquid chromatography and IL-6 level was measured prior to MPA administration, 4 weeks (in 59 cases) and 12 weeks (in 32 patients) after MPA administration by ELISA. Serum IL-6 level was significantly higher in recurrent cases, especially in those with visceral metastasis. Further, in patients for whom MPA therapy was effective, the IL-6 level prior to the treatment was clearly low. The IL-6 level was significantly increased after 4 weeks. However, response to MPA was significantly higher and PS was improved in those cases demonstrating less increased IL-6 levels after 4 weeks. In addition, the effect of MPA was significantly related to a higher serum concentration of MPA-positive ER, and longer disease-free interval, although there was no significant predictive factor for the clinical effect of MPA therapy in multivariate analysis. In conclusion, MPA therapy was effective in cases demonstrating a low IL-6 level and less increased IL-6 levels after 4 weeks. PS was improved in those cases in which the degree of IL-6 increase was suppressed by MPA, and many such cases showed low IL-6 levels prior to MPA therapy. Furthermore, PS was improved even in nonresponders to MPA. Therefore, it is suggested that MPA therapy might be useful in treating recurrent breast cancer, and its benefits might be mediated by IL-6.