{"doi":"10.17077/etd.005283","title":"The influence of preexisting mental illness, associated medication regimen factors, and access to care on breast cancer endocrine therapy adherence","abstract":"Oral endocrine therapy is a guideline-recommended treatment for estrogen receptor positive (ER+) breast cancer which reduces recurrence and mortality risk. Despite the serious nature of breast cancer, many patients are non-adherent to treatment. To improve cancer outcomes, efforts to identify populations at-risk and factors associated with non-adherence are warranted. This dissertation aimed to: (1) examine the prevalence of preexisting mental illness and its influence on breast cancer endocrine therapy adherence, (2) examine whether mental illness modifies the effects of adherence risk factors including prior medication (regimen complexity, number of medications and pharmacy visits) and financial burden, and (3) determine if primary care and mental health professional access and area socioeconomic factors are associated with endocrine therapy non-adherence and whether these factors disproportionately affect patients living with mental illness. Using the Surveillance, Epidemiology, and End Results cancer database linked to Medicare claims (SEER-Medicare), we selected women aged 68 and older at the time of their stage I-IV ER+ breast cancer diagnosis in 2007 to 2013. Included patients had continuous enrollment in fee-for-service Medicare Parts A and B for three or more years prior to cancer and 18 months or more after, and Part D for four months or more before and 18 or more after. Mental illness diagnoses were obtained from Medicare claims 36 months before cancer. Medication regimen factors in the four months before cancer included the count of unique medications used, pharmacy visits, and an administration complexity score subscale of the Medication Regimen Complexity Index. Access to care was measured using primary care and mental Health Professional Shortage Area (HPSA) assessments in a patient’s home county at the time of cancer diagnosis. Endocrine therapy outcomes included initiation and discontinuation (Cox regression), and adherence (longitudinal linear regression) as measured by the Proportion of Days Covered. Prior to breast cancer, 24.9% of patients had mental illness diagnoses, with unipolar depression (11.0%) and anxiety (9.5%) disorders most prevalent. Twenty percent of all women never initiated endocrine therapy and 25.7% of users discontinued. Continuous users for one year or longer had an 84% mean adherence rate. Patients with bipolar and psychotic disorders [HR 0.93 (95% CI 0.87-0.99)] and dementia disorders [HR 0.90 (95% CI 0.83-0.98)] were less likely to initiate. Those with anxiety [HR 1.21 (95% CI 1.09-1.34)] and substance use [HR 1.43 (95% CI 1.26-1.64)] disorders were more likely to discontinue. Those with substance use disorders had 2.3% lower average adherence rates. Patients who more frequently used medication and visited pharmacies in the four months prior to cancer (“4+ Meds & 2+ Visits”) were more likely to initiate [HR 1.47 (95% CI 1.33-1.63)] and adhere [+6.0% (95% CI 4.3-7.6)] and less likely to discontinue [HR 0.48 (95% CI 0.39-0.59)], relative to those who did not. In a focused analysis of patients with bipolar and psychotic disorders – who are less likely to initiate endocrine therapy – these protective factors were more common (they used more medications and visited pharmacies more often), but were nevertheless not prognostic of better initiation of maintenance of endocrine therapy in this subgroup. After adjustment for access to oncology care and patient characteristics, patients living in counties with the lowest primary care access were less likely to initiate endocrine therapy [highest shortage vs least HR 0.92 (95% CI 0.86-0.97)] but there was no association with daily adherence or discontinuation. Mental health shortage level was not associated with initiation, daily adherence, or discontinuation, overall or within subgroups with particular mental illness. However, patients who lived in counties not evaluated for mental health shortage were less likely to discontinue, including th","journal":null,"year":2020,"id":133835,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":0,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9539,"is_data_producer":false,"deposit_databanks":null,"is_oa":false,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2020-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":589885,"name":"Bradley McDowell","orcid":null,"position":1,"is_corresponding":false},{"id":401823,"name":"Bruce A. Smith","orcid":"0000-0003-1250-1710","position":2,"is_corresponding":false},{"id":247001,"name":"Robert Wallace","orcid":"0000-0002-5740-460X","position":3,"is_corresponding":false},{"id":589886,"name":"Elizabeth Chrischilles","orcid":null,"position":4,"is_corresponding":false},{"id":589887,"name":"Ryan Carnahan","orcid":null,"position":5,"is_corresponding":false},{"id":37943,"name":"Jess G. Fiedorowicz","orcid":"0000-0003-2057-4071","position":6,"is_corresponding":false},{"id":589712,"name":"Cole Haskins","orcid":"0000-0003-3760-8557","position":0,"is_corresponding":true}],"reference_count":0,"raw_metadata":null,"created_at":"2026-07-18T23:16:20.998822Z","pmid":null,"pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}