Facilitating adherence to endocrine therapy in breast cancer: stability and predictive power of treatment expectations in a 2-year prospective study

Abstract

Purpose

To identify modifiable factors predictive of long-term adherence to adjuvant endocrine therapy (AET).

Methods

As part of a 2-year cohort study in primary care (n = 116), we investigated whether initial treatment expectations predict adherence at 24 months after controlling for demographic, medical, and psychosocial variables. Treatment expectations were measured as necessity–concern beliefs, expected side-effect severity, and expected coping with side effects. Their stability over time and differences of trajectories between the adherent and nonadherent group were examined.

Results

Nonadherence at 24 months was 14.7% (n = 17). Side-effect severity at 3 months [OR 0.25, 95% CI (0.08, 0.81), p = 0.02] and necessity–concern beliefs [OR 2.03, 95% CI (1.11, 3.72), p = 0.02] were the sole predictors of adherence. Necessity–concern beliefs remained stable over 2 years, whereas expected side-effect severity (p = 0.01, η _p² = 0.07) and expected coping with side effects became less optimistic over time (p < 0.001, η _p² = 0.19), the latter particularly among nonadherers (p < 0.01, η _p² = 0.10).

Conclusions

Patients' initial necessity–concern beliefs about the AET and early severity of side effects affect long-term adherence. Expecting poor management of side effects may also facilitate nonadherence. We suggest that discussing benefits, addressing concerns of AET, and providing side-effect coping strategies could constitute a feasible and promising option to improve adherence in clinical practice.

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