Gender differences in persistency to bisphosphonates in patients with metastatic breast and prostate cancer

Bisphosphonates (BIS) treatment is a standard of care in metastatic bone disease (MBD) and regular intake is of upmost importance to ensure the effectiveness. The aim of this study was to investigate gender specific differences in persistence with BIS in MBD for the first time in this regard.

Out of the original database of 16 million patients, we extracted first-time metastatic cancer related BIS prescriptions from January 2001 to December 2011 in patients diagnosed with MBD following breast cancer (BC) or prostate cancer (PC). Patients were matched (1 : 1) in accordance to age. For persistence analyses, 1,007 patients with metastatic BC and PC were available.

After 1 year of follow-up, 35.3% of BC and 26.6% of PC patients treated with BIS discontinued their treatment (p < 0.001). The differences were irrespective of increased refill gaps and route of BIS administration. The multivariate hazard ratios of the Cox regression models for 1-year risk of BIS discontinuation (adjusting for multiple variables) showed no increased risk for treatment discontinuation for BC vs. PC patients (HR: 0.87; 95% CI: 0.65 - 1.17). The use of co-medications decreased, regional and insurance aspects increased the risk of treatment discontinuation (HR of 0.88, 1.50, and 1.42).

Although apparent in the primary analysis, we found no significant difference in the gender specific persistency after 12 months of first BIS treatment in MBD. Only co-medication, geographical and insurance aspects were associated with differences in discontinuation rates. Further studies are needed to investigate this clinically important relationship.