Clinical Features and Outcomes of Patients with Pancreaticobiliary Malignancies in Los Angeles County and Their Association with CA 19-9 Levels.

Simple Summary: Pancreaticobiliary malignancies (PBMs) are a leading cause of cancer-related deaths worldwide, with 611,722 deaths reported in 2020. Serum carbohydrate antigen (CA) 19-9 is a tumor marker commonly used clinically in the management of patients with PBMs. Several studies have demonstrated the utility of CA 19-9 levels as a marker of diagnosis, prognosis, and surveillance. However, few studies have specifically examined clinical presentations and outcomes in patients with low or undetectable CA 19-9 levels. The aim of our retrospective study was to examine the clinical features and outcomes of patients with tissue-proven cases of PBMs who had low CA 19-9 levels at diagnosis and compare them to those with normal and elevated CA 19-9 levels. Given the morbidity and mortality of PBMs, a better understanding of the role of CA 19-9 could lead to the tailored management of disease and, thus, improved outcomes in those with low CA 19-9 levels. Although CA 19-9 is a commonly used tumor marker in the management of PBMs, the literature describing outcomes in patients with PBMs who have undetectable or low (hereinafter "low") CA 19-9 levels remains scarce. In this study, we sought to compare clinical features and outcomes in patients with PBMs and low CA 19-9 levels to those with normal and elevated CA 19-9 levels. Methods: We retrospectively collected data on patients with biopsy-confirmed PBMs and stratified patients into categories based on their CA 19-9 level at diagnosis. Survival curves were estimated for patients in each of the three aforementioned CA 19-9 groups using the Kaplan–Meier method and compared using a Cox proportional hazards regression model. Results: Of the 283 patients identified, 23 (8.1%) had low, 70 (24.7%) had normal, and 190 (67.1%) had elevated CA 19-9 levels. After controlling for sex, age, BMI, the presence of metastases at the time of diagnosis, and treatment with curative intent, the hazard ratio for death in the elevated CA 19-9 group compared to the low CA 19-9 group was 1.993 (95% CI 1.089–3.648; p = 0.025). Conclusion: The elevated CA 19-9 level compared to the low CA 19-9 level and the presence of metastases were associated with an increased hazard of death, while treatment with curative intent was associated with a decreased hazard of death. [ABSTRACT FROM AUTHOR]