The objective of this study was to evaluate medical adherence for patients with ovarian cancer who initiated treatment with a PARP inhibitor therapy, and to identify factors associated with nonadherence.

We used the MarketScan Database to identify ovarian cancer patients who initiated PARP inhibitor therapy between January 1, 2008 and December 31, 2017. The primary outcome was adherence defined as ≥ 80% proportion of days covered (PDC). A secondary outcome included adherence assessed using the medication possession ratio (MPR). Multivariable logistic regression analysis was performed to assess relation between PDC and explanatory variables. Sensitivity analysis was performed to evaluate impact of dose-adjustments and toxicity-related delays on adherence.

Among 170,976 patients diagnosed with ovarian cancer, 151 patients met inclusion criteria. The median time from diagnosis to initiating therapy was 33 months. Overall, 40 (26.5%) were non-adherent based on a PDC less than 80%. Non-adherent patients were more likely to receive niraparib and have a longer duration of therapy (p < 0.05). We found no significant impact of age, comorbidities, insurance plan, or year of PARP inhibitor initiation on non-adherence. In a sensitivity analysis to assess different definition of adherence, non-adherence ranged from 11.3% to 41.1%. When accounting for possible dose-adjustments, 21.2% of patients were non-adherent.

This population based study of ovarian cancer patients found that a quarter of patients may be sub-optimally adherent to PARP inhibitor therapy. Future research should focus on identification of patients at risk for nonadherence and interventions to lower nonadherence among these patients.