Breast Cancer History Promotes Vertebral Fracture Risk

Heidi Splete

November 22, 2021

Women with a history of stage III to stage IV breast cancer had significantly more pathologic vertebral fractures compared to those with stage I and stage II disease, based on data from approximately 5,000 adult women.

Breast cancer remains associated with increased fracture risk in part because of estrogen deficiency, aromatase inhibitors, frailty, and skeletal metastases, wrote Joan C. Lo, MD, of Kaiser Permanente Northern California, Oakland, and colleagues. Fractures associated with these factors have been studied, but many of the existing epidemiologic studies lack detail on fractures related to cancer, they noted. The researchers examined the association between pathologic fractures and major osteoporotic fractures in women with invasive breast cancer who received endocrine therapy.

In a study published in JAMA Network Open (2021 Nov 18. doi: 10.1001/jamanetworkopen.2021.33861), the researchers reviewed data from 5,010 women enrolled in the Pathways Study (3,312 women) or Research Program on Genes, Environment, and Health (RPGEH) study (1,698 women) with newly diagnosed invasive breast cancer who received endocrine therapy. The women were followed for up to 10 years for incident fracture, with a median follow-up period of 6.7 years.

The average age of the women was 60.2 years; 73.3% were non-Hispanic White, 4.9% were Black, 9.4% were Hispanic, and 1.6% were women whose ethnicity was unknown. Approximately 90% of the women were at stage I to stage II at initial diagnosis.

Overall, 340 (6.8%) had incident fractures during the follow-up period. The incident fractures included 46 hip, 104 vertebral, 78 humerus, and 137 wrist fractures. Significantly more women with hip fracture (43.5%) were age 80 years or older, compared with less than 25% of women with vertebral fractures (22.1%), humerus (19.2%), or wrist fracture (15.3%).

Pathologic fractures accounted for 22 of 104 incident vertebral fractures (21.2%) and fewer than 5 of 46 incident hip fractures (8.7%); few wrist and humerus fractures were pathologic. According to tumor stage, 15 of 87 (17.2%) vertebral fractures in women with initial stage I and II were pathologic, compared to 7 of 17 (41.2%) in women with initial stage III to stage IV breast cancer (P < .05).

The results emphasized the need to consider vertebral fracture risk in women with breast cancer, notably advanced stage cancer, as approximately one-third of the incident vertebral fractures in this subset of patients was deemed cancer-related, the researchers noted.

"As the axial skeleton is a common site for breast cancer metastasis and vertebrae a common site for pathologic fracture, primary care physicians should consider the possibility of pathologic fracture in women with higher risk based on advanced-stage cancer history," the researchers wrote.

The study findings were limited by several factors, including the lack of data on fracture risk factors, treatment, and chemotherapy, and the inclusion only of clinically diagnosed fractures and not asymptomatic vertebral fractures, the researchers noted. However, the results were strengthened by the large sample size and comprehensive fracture assessment, they said. Additional studies to examine nonpathologic fracture risk according to breast cancer treatment, such as the use of aromatase inhibitors versus cytotoxic chemotherapy, may inform which women would benefit from more aggressive osteoporotic fracture prevention, they concluded.

Findings Inform Shared Decision-Making

"This study highlights the apparent association between an initial diagnosis of stage III or IV breast cancer and an increased risk for pathologic vertebral fracture," said Constance Bohon, MD, a gynecologist in private practice in Washington, D.C., in an interview. "Most likely this finding is secondary to breast cancer metastases," Bohon noted. However, she questioned whether there is a difference in fracture rates between women who received only aromatase inhibitors, those who received tamoxifen, and those who received both treatments.

"Additional data to determine the age of menopause, exercise frequency, current weight, and family history of osteoporosis may serve to identify those at highest risk for pathologic vertebral fracture," said Bohon. "Until further data are available, clinicians should review this study and counsel their patients regarding options to potentially mitigate their apparent increased risk for pathologic vertebral fracture," she emphasized.

The study was supported by the National Cancer Institute, National Institutes of Health, and the Research Program on Genes, Environment, and Health of Kaiser Permanente Northern California. The researchers had no financial conflicts to disclose. Bohon had no financial conflicts to disclose but serves on the Editorial Advisory Board of Ob.Gyn. News.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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