Abstract
e20604 Background: Bronchiolo-alveolar carcinoma (BAC) is a rare subtype of non-small cell lung cancer of the lung periphery, often characterized by lepidic growth. Although BAC has undergone various reclassifications in recent years, International Classification of Disease codes still classifies these subtypes using the same codes that previously belonged to BAC. Changing diagnostic criteria and other factors cause BAC to be among the most overdiagnosed forms of lung cancer and thus a demographic study could provide insight into trends. Methods: A retrospective cohort analysis utilizing the National Cancer Database (NCDB) from 2004 – 2020 included patients with malignant forms of BAC (Invasive mucinous adenocarcinoma, mixed invasive mucinous, and nonmucinous adenocarcinoma) confirmed through histology. Demographic factors such as sex, age, race, Hispanic status, median household income, insurance status, facility type, county population, distance from facility, and Charlson Deyo score were analyzed by descriptive statistics and incidence trends. Results: In total, 12,607 patients were identified in the database with a confirmed diagnosis of BAC between 2004 – 2020. The number of cases per year remained steady (mean = 565.4) until 2018. From 2018 to 2020, the average number of diagnoses per year was 1575.0. The average age of diagnosis was 69.3 years (SD = 10.7, range = 10 to > 90 years). 58.1% of the cases were female patients. The top primary sites were the lower and upper lobes (46.2% and 39.9% respectively). The majority (59.2%) had Charlson-Deyo comorbidity scores of 0. Most cases occurred in Non-Hispanic White persons (86.8%). More patients were in the top quartile of income earners (34.0%) compared to those in lower quartiles. Medicare was the insurance provider for most patients (65.0%). More patients were diagnosed in counties with a population over 1 million (52.4%). More patients were treated in comprehensive community cancer programs (38.1%) followed closely by academic cancer programs (35.2%). Patients lived an average of 31.6 miles (SD = 113.0, range = 0.1 – 2390.7) from the treatment facility. Conclusions: This is the first NCDB analysis on the demographics of BAC. The sudden rise in cases per year in 2018 aligns with the changing pathologic and histologic definitions for BAC. A 2006 review of BAC found that 50-70% of cases occur in female patients, similar to our results. The majority of BAC patients tend to be non-Hispanic and White with a primary site diagnosis in the lower lobe, followed by the upper lobe. BAC patients are more likely to be in the top income quartile, live in densely-populated metropolitan areas, and receive treatment in a non-academic program. Further research is needed to better understand the impact of demographic, socioeconomic, and environmental factors on the diagnosis and prognosis of BAC, especially because its diagnostic criteria have changed recently.