A population-based registry study of extended bisphosphonate use: minimal shift after landmark publications about shorter treatment duration.

Abstract

Optimal duration of bisphosphonate therapy was unknown until the FLEX study was published in 2006 showing a 5-year course to be adequate for most women. In 2008 a link between long-term bisphosphonate and atypical femoral fractures was reported and confirmed in later studies. We hypothesized these landmark observations should have led to a decrease in use of bisphosphonates for >5 or 10 years, from 2010 onward. The Manitoba BMD registry with linkage to provincial pharmacy data was used to determine the percentage of long and very-long term bisphosphonate users from therapy start. The cohort comprised women age > 50 with BMD between 1995-2018 with oral bisphosphonate first prescribed for >90 days with adherence >75% in the first year. For each calendar year of continued therapy, the percentage of patients and medication possession rate was tabulated. The percentage of users beyond 5 years was compared between patients who started therapy in 1998-2004 (those taking 5 years of therapy still finish prior to 2010) versus 2005-2012 (all new therapy starts overlap 2010 in those taking ≥5 years treatment). The cohort included 2991 women with mean follow up 8.8(1.3) years, 64.9% of whom took continuous oral bisphosphonate for >5 years and 41.9% for >10 years. In the earlier vs later era, there were 74.4% vs 70.2% who completed 5 years. With respect to longer treatment, there were 68.0% and 60.5% of patients treated for 6 or more years (p < 0.0001) and 46.6% vs 33.5% treated for >10 years (p = 0.08). Medication possession rate was >79% in every year of therapy. Landmark studies leading to more limited bisphosphonate courses may have slightly reduced longer-term treatment, but up to one-third of adherent patients in the modern era still receive continuous bisphosphonate therapy for >10 years. This article is protected by copyright. All rights reserved.