Abstract P3-07-17: Rates of adherence and persistence to adjuvant endocrine therapy among women enrolled in Medicare Part D in a four-state region of Appalachia
Authors: Kimmick Gretchen G , Camacho Fabian , Anderson Roger T 
Published: May 2015

Background: Disparities exist in breast cancer outcomes by age, geographic location, and socioeconomic status, but there is little data regarding contributing factors to disparities within Appalachia. Underuse of adjuvant endocrine therapy for breast cancer can contribute to disparities. We studied older women within four states of Appalachia and explored adherence and persistence rates for adjuvant endocrine therapy.

Methods: The study group consisted of women with stage I-III breast cancer diagnosed 2008-2009 in North Carolina, Pennsylvania, Kentucky, and Georgia, who were continuously enrolled in Part D Medicare and filled a prescription for tamoxifen, anastrozole, letrozole, or exemestane. Adherence rate is defined by medication possession ratio (MPR=sum of days supply for all claims during the calendar year after first prescription). Persistence rate was defined as absence of a 90 day or greater gap in prescription coverage since the first prescription fill. Univariate analyses by Kruskall-Wallis nonparametric test were performed. Variables included age, year of diagnosis, Charlson comorbidity score, Medicaid/Medicare versus Medicare insurance status, rural versus urban residence, county-level economic status (Appalachia Regional Commission: Distressed, At risk, Transitional, or Competitive), state, stage (1, 2A, 2B, or 3), and breast conserving surgery (BCS) versus mastectomy.

Results: We identified 726 eligible cases. Mean age was 75.1 years (range 41-98); 97.9% were white; 47.9% had rural residence, 9.5% lived in distressed counties, 29.1% were dual-Medicaid/Medicare insured, mean Charlson comorbidity score was 1.66, and tumor was stage 1 in 56.6%, 2 in 33.6%, and 3 in 9.8%. Mean MPR was 57% (SD 0.27). Persistence rate at 6-months was 79% (SD 0.41) and at 12-months was 36% (SD 0.48).

MPR varied significantly within age groups (p=0.01), county-level economic status levels (p=0.01), and Singh Index Area Deprivation tertiles (p=0.01). Mean MPR increased with increasing age: 48% for age 40--65, 55% for age 66-75, 59% for age 76-85, and 63% for age 86 and older. MPR was highest among those in the Competitive ARC class at median levels of 64%, versus 53% in Distressed, 58% in At Risk, and 58% in Transitional. Greatest area deprivation tertile also coincided with lower mean and median MPR adherence.

Persistence at 12 months varied significantly among age groups (p=0.01), and type of surgery (p=0.04). Persistence rates were lower in younger cases: 23% for age 40-65, 34% for age 66-75, 37% for age 76-85, and 49% for age 86 and older. Persistence rates were 32% in those who had BCS and 42% in mastectomy. Persistence rates varied significantly among comorbidity levels (p=0.0260); but, after adjusting for age and using logistic regression, this association was only marginally significant (p=0.05). Adjusted expected persistence increased as comorbidity score increased: 28% for 0; 35% for 1; and 39% for 2 or more.

Conclusions: Among this group of women within four states in Appalachia with Medicare Part D who filled a prescription for endocrine therapy, overall adherence and persistence rates were low. Higher adherence and persistence rates were seen in older age groups.

Citation Format: Gretchen G Kimmick, Fabian Camacho, Roger T Anderson. Rates of adherence and persistence to adjuvant endocrine therapy among women enrolled in Medicare Part D in a four-state region of Appalachia [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P3-07-17.