Provider- and patient-level predictors of oral anticancer agent initiation and adherence in patients with metastatic renal cell carcinoma.
Authors: Spees Lisa , Wheeler Stephanie B. , Jackson Bradford E. , Baggett Christopher , Wilson Lauren E. , Greiner Melissa A. , Kaye Deborah , Zhang Tian , George Daniel J. , Scales Charles D. , Pritchard Jessica , Leapman Michael S. , Gross Cary Philip , Dinan Michaela Ann 
Published: September 2021

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Background: While several patient-level factors have been associated with oral anti-cancer agent (OAA) initiation and adherence for metastatic renal cell carcinoma (mRCC) and other cancers, few provider-level factors have been examined, despite providers being a key component driving OAA access. We examined provider and patient characteristics associated with OAA initiation and adherence among individuals with mRCC. Methods: We used linked North Carolina state cancer registry data and multi-payer claims data to identify mRCC patients diagnosed in 2004-2015. A patient’s modal provider was the provider most frequently on claims with a diagnosis code of RCC or metastatic cancer between 2 months prior to and 3 months following the index date. Provider-level variables included specialty, sex, race/ethnicity, years in practice, provider’s RCC patient volume, and practice location. Patient-level control variables of interest included: age at metastatic diagnosis, sex, race/ethnicity, rural location, insurance coverage at metastatic index date, histology, stage at initial diagnosis, radical/partial nephrectomy in the prior year, number of comorbidities at baseline, and frailty. OAA initiation within the 12 months following the patient’s metastatic index date was identified from prescription drug files and pharmacy claims. Adherence to OAAs was defined as having ≥80% proportion of days covered (PDC) for the 90 consecutive days following an initial OAA claim that patients had access to any OAA days’ supply. We estimated risk ratios (RR) and corresponding 95% confidence limits (CL) using modified Poisson regression to evaluate patient- and provider-level factors associated with OAA initiation and adherence. Results: Of the 687 patients in our sample, 37% initiated an OAA following mRCC diagnosis. Patients with a modal provider specializing in hematology/medical oncology were more likely to initiate OAAs than those seen by other specialties (i.e., urology/urological surgery, internal medicine, and other). Compared to patients treated by providers practicing in both urban and rural areas, patients with providers practicing in urban areas only more likely to initiate OAAs (RR = 1.37; 95%CL:1.09,1.73). Patients who were older, with more comorbid conditions, stage I at initial diagnosis, and greater frailty were less likely to initiate OAAs. Among the 207 patients who initiated an OAA and survived the following 90 days, the median PDC was 0.91. No provider-level factors were associated with OAA adherence. However, Medicare-insured patients were less likely to be adherent (RR = 0.61; 95%CL:0.42,0.87) than those with private insurance. Conclusions: Our results suggest that provider- and patient-level factors are associated with OAA initiation but only patient-level factors are associated with adherence.