Bone mineral density in breast cancer patients with estrogen receptor-negative tumor

We read with great interest the article by Douchi et al. [ ] in which they showed that postmenopausal breast cancer patients with positive estrogen receptor (ER) tumor status have higher bone mineral density (BMD) than age-matched, healthy postmenopausal women. However, as they pointed out that those ER-negative patients were not included in their study because of small size. Recent study from M.D. Anderson Cancer evaluated the association of BMD at the time of diagnosis with clinical-pathologic findings (history of hormone replacement therapy, existence of in situ component, estrogen and progesterone receptor concentrations, tumor size, nodal status, stage, grade, existence of lymphovascular invasion, and histology) in patients with 117 operable postmenopausal breast cancer [ ]. Median age at diagnosis was 62 (range 49–83). Sixty-two patients had stage I disease and 55 had stage II disease. Patients with higher BMD were found to have low grade disease (P = 0.01 for lumbar spine BMD and P = 0.09 for total hip BMD), no lymphovascular invasion (P = 0.02 for lumbar spine BMD and P = 0.03 for total hip BMD) and progesterone receptor-positive tumors (P = 0.05 for lumbar spine BMD). Patients with low Ki-67 level also tended to have high BMD (P = 0.06 for lumbar spine BMD). However, linear regression models for lumbar and hip BMD, adjusting for age showed there was no difference between ER-positive (n = 103) and ER-negative (n = 6) breast cancer patients (P = 0.25 and 0.99, respectively). Although ER-negative patients in this study are in small size, this preliminary result may suggest that estrogen may also play a role in the pathogenesis of ER-negative postmenopausal breast cancer patients. This proposal should be tested in large prospective studies.