Assessing the rate and quality of breast cancer treatment following initial diagnosis.

147 Background: Breast cancer is the most diagnosed and second most deadly cancer among women in the United States. Diagnosis of breast cancer consists of imaging with biopsy of suspicious lesions and is managed by diagnostic radiologists. Subsequent breast cancer treatment is managed by an independent oncology team, generally consisting of surgery and radiation therapy (RT). Due to the compartmental nature of the diagnosis and treatment of breast cancer, it is possible that patients diagnosed with the disease may not receive adequate care. This lack of guideline-concordant care (GCC) could lead to increased morbidity and mortality among breast cancer patients. Methods: All patients receiving a breast cancer diagnosis between 9/1/19-9/1/24 were compiled using a National Cancer Institute-designated cancer center deidentified database. The primary outcome was the proportion of diagnoses that received GCC. GCC was defined in accordance with the National Comprehensive Cancer Network (NCCN) as the treatment of patients with American Joint Committee on Cancer (AJCC) Stage 0-III breast cancer with 1) mastectomy alone, 2) lumpectomy and RT, or 3) lumpectomy alone for patients ≥ age 70. Secondary outcomes included the proportion of patients diagnosed with breast cancer who received GCC by AJCC stage and the proportion of patients diagnosed with breast cancer who received GCC in the six months before and after 4/1/20. Results: 1,455 cases of AJCC Stage 0-III breast cancer were diagnosed. Although 981 (67.4%) received some form of treatment, only 515 (35.4%) received GCC. Of patients diagnosed with breast cancer, 84/232 (36.2%) with Stage 0, 327/880 (37.2%) with Stage I, 70/244 (28.7%) with Stage II, and 34/99 (34.3%) with Stage III received GCC. Of patients treated for breast cancer, 84/154 (54.5%) with Stage 0, 327/587 (55.7%) with Stage I, 70/165 (42.4%) with Stage II, and 34/75 (45.3%) with Stage III received GCC. In the six months before 4/1/20, 61/146 (41.8%) of Stage 0–III patients received GCC, compared to 53/107 (49.5%) in the six months after. Conclusions: Only 35.4% of patients diagnosed with breast cancer received confirmed GCC, despite 67.4% undergoing some form of treatment. GCC rates were suboptimal across all AJCC stages, with Stage II patients receiving the least appropriate care. While the COVID-19 pandemic posed significant healthcare challenges, the slightly improved GCC rates observed after April 2020 suggest that these disruptions did not worsen the systemic issues that existed. The lack of improvement in GCC with increasing stage highlights that coordination gaps affect patients broadly, regardless of disease severity. These findings emphasize the need for improved transitions from breast cancer diagnosis to treatment, better care coordination, and system-level interventions to ensure that patients receive timely and appropriate care. Systemic integration of patient navigation could address these issues.