Calcitriol and weight-bearing exercise were both found to be feasible and well-tolerated interventions among patients with breast cancer experiencing cancer treatment-induced bone loss (CTIBL), but only calcitriol was associated with significantly improved bone formation, according to a study published in Supportive Care in Cancer.

CTIBL is associated with decreased endogenous estrogen levels after long-term treatment with chemotherapy or hormone therapy, leading to a significantly increased risk of fractures among breast cancer survivors. Bisphosphonates are the standard for osteoporosis therapy, but prolonged use has been associated with osteonecrosis of the jaw and atypical femoral fractures; additional therapeutic options are necessary for this patient population.

For this study, researchers randomly assigned 41 breast cancer survivors actively maintained on hormone therapy to 4 study arms: intermittent calcitriol 45 mcg/week, exercise with resistance training and progressive walking, both, or daily multivitamins. Researchers assessed bone metabolism biomarkers (N-telopeptides of type I collagen [NTx] and bone-specific alkaline phosphatase [BSAP]) to analyze bone formation and resorption.

Results demonstrated that patients treated with calcitriol significantly improved bone formation and also had a nonsignificant increase in the bone modeling index.

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Of the patients assigned to aerobic exercise, 100% adhered to their training regimens compared with just 44.4% of those assigned to resistance training. Outcomes showed that exercise did not improve any bone biomarkers, but the authors noted that these findings may have been affected by poor compliance.

Hypercalcemia, a commonly observed adverse event associated with calcitriol once or twice daily, only occurred in 3 patients at no greater than grade 1 severity.

The authors concluded that “[f]urther studies are needed to confirm these findings. Future studies may use this calcitriol regimen in conjunction with existing bone drugs to increase efficacy.”

Reference

Peppone LJ, Ling M, Huston AJ, et al. The effects of high-dose calcitriol and individualized exercise on bone metabolism in breast cancer survivors on hormonal therapy: a phase II feasibility trial [published online February 22, 2018]. Support Care Cancer. doi: 10.1007/s00520-018-4094-4