Objetive

To assess the persistence of aromatase inhibitor (AI) therapy, mortality associated with treatment discontinuation and the influence of oral bisphosphonates (BP) in routine clinical practice.

Material and methods

Prospective observational study of women with breast cancer undergoing AI treatment between January 2006 and December 2015, registered in the SIDIAP database. Those previously treated with tamoxifen were excluded. AI persistence was studied with a survival analysis: the Kaplan-Meier estimator was calculated, and a proportional hazards model (Cox regression) was performed between users and non-users of BP adjusting for age. A sensitivity analysis was carried out taking into account mortality as a competitive risk (Fine and Gray models). The difference in mortality between groups was compared using a Chi square test.

Results

A persistence to AI of 87% was observed after 5 years of treatment, with an overall mortality of 19.75%. There was 7.7% less mortality in those patients who completed the 5 years of treatment compared to those who did not. Patients with BP showed a decrease in mortality (6.6%) and a decrease in the risk of discontinuing therapy (adjusted SHR:

0.62 [95% CI: 0.55 to 0.70]) compared to non-users.

Conclusions

Persistence to AI and BP use are associated with a decrease in overall mortality. Furthermore, the use of BP increases adherence to AI treatment.

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