Clinical determinants of survival in patients with stage II-III pancreatic cancer.

56 Background: We sought to identify the clinical determinants of overall survival (OS) in patients diagnosed with stage II-III pancreatic cancer not undergoing surgery. We curated a relatively homogenous cohort of patients who did not undergo surgical resection, but instead underwent chemotherapy in sequence with stereotactic body radiation therapy (SBRT) to examine the features that differentiated those with poor OS. Methods: In a retrospective study, we examined a cohort of 259 patients with stage II-III pancreatic cancer who underwent chemotherapy in sequence with SBRT without surgery at a single institution (Stanford Health Care). We conducted both univariate and multivariate Cox regression analyses to assess the relationships between OS and individual clinical and tumoral variables, including: age, sex, stage, Karnofsky performance status (KPS), body mass index, vessel involvement, tumor location, and biological equivalent dose [BED] of SBRT as potential determinants. Results: The study cohort consisted of 136 men (52.5%) and 123 women (47.5%) with a median age of 69 (range 38-94). Tumor histology was predominantly ductal adenocarcinoma (n=249, 96.1%), with tumor sites of involvement spanning: uncinate (n=35, 13.5%), head (n=160, 61.8%), body (n=59, 22.8%), and tail (n=5,1.9%). More patients had stage III (n=171, 66%) than stage II (n=88, 34%) disease, and their tumor resectability by NCCN criteria were rated as: unresectable (n=145, 56%), borderline (n=28, 10.8%), resectable (n=11, 4.2%), or unrecorded (n=75, 29%). Tumor progression was observed in local (n=71, 27.4%), regional (n=29, 11.2%), and distant (n=150, 57.9%) sites during the median follow up period of 17 months (range 15-18 months) from diagnosis and 12 months (10-13 months) from SBRT. Death (n=213, 82.2%) during this period was more common than survival (n=46, 17.8%). In univariate analyses, clinical features impacting OS included: KPS (hazard ratio [HR] 0.14, p=0.007); male sex (HR 1.44, p=0.01), pancreatic head tumors (HR 1.44, p=0.011), BED (HR 1.33, p=0.035), and age (HR 1.013, p=0.044). In the multivariate analysis, which incorporated only features significant in the univariate analyses, tumor location at the pancreatic head (HR 1.412, p=0.021) and male sex (HR 1.360, p=0.03) conferred the highest risks for poor OS, with BED bordering on significance (p=0.059) (Table). Conclusions: Among patients with stage II-III pancreatic cancer who underwent chemotherapy in sequence with SBRT, but not surgery, the most significant clinical determinants of poor OS were location of the tumor in the pancreatic head and male sex. Prioritizing additional disease monitoring and alternative therapies for this subset of patients at higher risk of poor survival may be warranted. [Table: see text]