Bone metastasis is common in breast cancer. No previous study evaluated the usefulness of bone modifying agents (BMA) in breast cancer patients whose metastases are limited to non-weight bearing bones.
We retrospectively collected data at St. Luke’s International Hospital between 2006 and 2016. Weight bearing bones were defined as vertebral body, lower limbs, and pelvis, and all the other bones were defined as non-weight bearing bones. Breast cancer patients, age ≥20 years old, who were newly diagnosed to have bone metastasis only in non-weight bearing bones were included in this study. Bone metastases were detected by either bone scintigraphy or PET-CT. The selected patients were divided into 2 groups: patients of Group A started BMA within 3 months from the diagnosis, and those of Group B did not start BMA within the 3 months. We are interested in comparing the Groups A and B in terms of time to skeletal related events (SRE) and overall survival (OS), where SRE were defined as orthopedic surgery, percutaneous vertebroplasty, and/or palliative radiation to bone metastasis.
Out of 418 breast cancer patients with bone metastasis, only 101 patients were found to have bone metastasis only in non-weight bearing bones. The median follow-up time was 32 months. The number of patients in Group A and B were 54 and 47, respectively. Eight patients in Group A and 5 patients in Group B developed SRE (p = 0.568). Median SRE free survival (i.e. timeto SRE) was 118.5 months, and 117.3 months in Group A and Group B, respectively (p = 0.490, Hazard ratio: 1.48). Median overall survival (OS) was 39.7 months in group A and 78.3 months in group B (p = 0.203, Hazard ratio: 1.45).
Early initiation of BMA did not improve SRE free survival or OS in breast cancer patients who have only non-weight bearing bone metastasis. Further prospective studies are needed to confirm this finding.
Clinical trial identification
Legal entity responsible for the study
St. Luke's International Hospital.
Has not received any funding.
All authors have declared no conflicts of interest.