ONJ With Bone-Modifying Agents in Breast Cancer Patients

Alexander M. Castellino, PhD

October 22, 2018

MUNICH — The side effect of osteonecrosis of the jaw (ONJ) that is seen with bone-modifying agents in patients with osteoporosis is also seen in patients with metastatic breast cancer who take these drugs. New data on the prevalence of this side effect in the breast cancer population was presented here in a poster (349P) at the European Society for Medical Oncology (ESMO) 2018 annual meeting.

"Our findings are of significant value since they reflect the patterns of care and complications associated with these commonly used agents in the general population," say the researchers, led by Mariana Chavez MacGregor, MD, of the MD Anderson Cancer Center in Houston, Texas.

The researchers set out to determine the pattern of usage of bone-modifying agents and the incidence of ONJ in older women with metastatic breast cancer using a large, nationally represented cohort of such patients who had evidence of bone metastases.

They identified women diagnosed with de novo metastatic breast cancer between 2007 and 2013 from a SEER-Medicare database. They included only women with bone metastases in their analysis based on claims. To be included in the analysis, patients were required to receive anticancer therapy within a year of diagnosis.

Healthcare Common Procedure Coding System (HCPCS) codes were used to identify patients who received bisphosphonates; ONJ and fractures were identified using ICD-9 codes.

For the 1528 patients in the analysis, median age was 75 years. Within 1 year of their metastatic breast cancer diagnosis, 71% of the patients received bone-modifying agents — most received bisphosphonates (68%), 27% received denosumab, and 5% received both.

Based on the odds ratio (OR), the researchers reported that older patients (OR, 0.64), patients with comorbidities based on Charlson score (OR, 0.6), or full/partial state buy-in patients (a surrogate for poverty) (OR, 0.65) were less likely to receive bone-modifying agents.

Median time from the first dose of a bone-modifying agent to development of ONJ was 21 months.

The team found 19 cases of ONJ, and all in patients who were treated with bone-modifying agents, giving an overall incidence rate of 1.7%. The 2-year and 4-year cumulative rates of ONJ were 1.4% and 4.0%, respectively.

Incidence rates were higher in patients receiving denosumab. The 2-year cumulative incidence rate of ONJ was 0.9% for bisphosphonate users and 2.7% for denosumab users. Corresponding 4-year rates were 1.4% and 4%.

The researchers were unable to identify any clinical predictors of ONJ.

European Society for Medical Oncology (ESMO) 2018 Congress. Abstract 349P.

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