Side effects of endocrine drugs indicate success in breast cancer treatment

The study, published onine in The Lancet Oncology, comes from Jack Cuzick and colleagues from Cancer Research UK and Queen Mary School of Medicine and Dentistry, University of London. The symptoms that arise during endocrine treatment come from oestrogen depletion or oestrogen blockage.

Their analysis used data on women who participated in the Arimidex, Tamoxifen, Alone or in Combination (ATAC) trial, a study designed to assess tamoxifen or anastrozole for adjuvant therapy of post-menopausal breast cancer. To test for a relationship between the toxicity symptoms and cancer recurrence, the researchers compared two groups of women with hormone-receptor-positive tumors: one group reported symptoms at their first follow-up visit in the ATAC trial, and the second group did not report symptoms.

After three months of treatment, 37.5% of eligible women reported new vasomotor symptoms. These women had a 9-year cancer recurrence rate of 23%, while women without new vasomotor symptoms had a recurrence rate of 18%. The 31.4% of women who reported new joint symptoms after three months of treatment had a 9-year cancer recurrence rate of 14%, while those without joint symptoms had a 23% recurrence rate. Women who received both tamoxifen and anastrozole exhibited these rate differences, and anastrozole was linked to lower recurrence rates than tamoxifen independent of the presence of symptoms.