Breast cancer patients receiving denosumab during adjuvant aromatase inhibitors treatment: who are the "inadequate responders" patients to denosumab?

Purpose: Adjuvant hormone therapy with aromatase inhibitors (AIs) through the induction of tissue hypo-estrogenism induces an increase in osteoclast activity and inhibition of osteoblast activity through the production of RANKL. This is a relevant cause of comorbility in women affected by breast cancer with negative impact on quality of life. We conducted an observational study on patients treated with AIs and denosumab to compare responders and inadequate responders.

Methods: The study design was a historical cohort survey that represented a 42-month follow-up period for patients on hormone treatment with AI for breast cancer and concomitant denosumab (Prolia®) at 60 mg subcutaneously every 6 months. Sixty-eight patients treated consecutively at our Medical Oncology Unit were studied. The comparison was carried out by stratifying on the basis of age, body mass index (BMI), weight, carboxy-terminal collagen crosslink (CTX), lumbar spine and femoral T-scores, FRAX 10-year probability of a fracture, FRAX 10-year probability of a major osteoporotic fracture at baseline and at the end of follow-up.

Results: Calculating and comparing the FRAX 10-year probability of hip fragility fracture at baseline in the subgroup of responders and in the inadequate responders subgroup, we found a statistically significant difference (p=0.039). Similarly, a statistically significant difference was found between the two subgroups of patients in terms of FRAX 10-year probability of hip fragility at the end of follow-up (p=0.014) and FRAX 10-year probability of a mayor osteoporotic fracture at the end of follow-up (p=0.043).

Conclusion: This study suggests the need to control weight in breast cancer survivors and adjuvant AIs treatment in order not only to reduce the incidence of disease relapse but also to safeguard bone health undergoing treatment with denosumab. Indeed, patients tend to respond inadequately to denosumab if they are not careful to control their body weight.