OBJECTIVES: Increasing utilization of non-cycled antineoplastic therapies for a variety of cancers has generated interest in applying a proportion of days covered (PDC) adherence metric, and examining costs and health outcomes associated with adherent PDC (≥80%).

METHODS: This retrospective study used MarketScan Commercial Claims and Encounters databases from 2017--2019. PDC was calculated for 2018 or 2019 utilizing non-cycled medications (monthly dosages for 31 products) from 15 therapeutic categories. New therapy/diagnosis indications were inferred from the 2017 files. Continuous enrollment was required as were ICD oncology diagnosis codes for those 18—65 years of age. Sample exclusion criteria were deaths, hospice care, inpatient transplant services, and females on fertility therapy. Models examined adherence level (PDC≥80% or not) and 9 covariates, with interaction terms, for significant associations on medical costs (inpatient and outpatient), hospitalizations, and length of days stay (LOS). Finally, for patients meeting 2019 PDC criteria, combined yearly results were modeled for associations.

RESULTS: Of the 5,694 patients meeting 2018 PDC criteria, 2,034 retained a 2019 PDC, with adherence at 73.2% in 2018 and 67.9% in both years. In 2018, 34.8% were new to therapy/diagnosis and a mean age was 52.4 years. In 2018, 16.2% were hospitalized with LOS=9.5, and 24.1% were hospitalized in both years with LOS=8.8. Models for 2018 found significant effects favoring the adherent cohort with reduced medical costs (-$9,600, p<.0001), odds of hospitalization (0.72, p<.0007), and oncology-related LOS (-1, p<.02). Results for combined years indicated adherence effects for reduced medical costs (-$9,356, p<.0001), odds for hospitalization (0.6, p<.0002), and oncology-related LOS (-2.9, p<.0007). Significant covariate interactions are discussed in the poster.

CONCLUSION: Remaining adherent to oral antineoplastic therapy was associated with lower medical costs, fewer hospitalizations, and a shorter LOS, even across multiple years. These reductions were dependent on comorbidities, new to therapy/diagnosis, or metropolitan area.