BACKGROUND: Risk factors for breast cancer relapse are well-known, such as large tumour size or lymph node involvement. The aim of our study was to analyse the influence of bone mineral density, fractures and bisphosphonate or vitamin D prescription on 10 years' breast cancer outcome.

PATIENTS AND METHODS: This is a longitudinal and prospective cohort of 450 postmenopausal women with local oestrogen receptor (ER)+ breast cancer. For every patient, we analysed tumour characteristics, bone status at the beginning of aromatase inhibitor treatment and 10 years' cancer outcome with Cox model.

RESULTS: Mean follow-up was 10.3 ± 3.0 years. Seventy nine women died, and 75 had a relapse; 30.7% had a history of fracture, 16.9% had a T-score ≤ -2.5 and 11.3% had vitamin D deficiency. Bisphosphonates were prescribed to 35.3% women for osteoporosis for a mean duration of 5 ± 1.7 years. Tumour size (hazard ratio [HR] = 1.32, P ≤ 0.01) and the number of lymph nodes involved (HR = 1.07, P = 0.03) were significantly associated with relapse. Bisphosphonate treatment was significantly associated with a decreased risk of relapse (HR = 0.51, P = 0.03). Age at cancer diagnosis (HR = 1.07, P ≤ 0.01) and vitamin D deficiency (HR = 1.85, P = 0.04) were significantly associated with an increased risk of death, whereas bisphosphonate treatment was associated with a decreased risk of death (HR = 0.46, P = 0.01).

CONCLUSION: Osteoporosis treatment, including vitamin D and bisphosphonates, is associated with a 50% reduction of relapse and death in women treated with aromatase inhibitors for ER+ breast cancer.