Clinical Outcome and Prognostic Factors of Pancreatic Adenosquamous Carcinoma Compared to Ductal Adenocarcinoma—Results from the German Cancer Registry Group

SIMPLE SUMMARY: About 0.5% of pancreatic malignancies are adenosquamous carcinomas. The pathophysiology of these carcinomas is poorly understood and clinical data is sparse. We compared characteristics and prognostic factors of adenosquamous carcinoma and ductal adenocarcinoma, which represent the most common type of pancreatic cancer based on data from the German cancer registry group. Adenosquamous carcinoma showed poorer differentiation and higher frequency of blood vessel invasion indicative of a more aggressive tumor biology. Adenosquamous tumor differentiation was a strong negative prognostic factor. Survival of patients with adenosquamous carcinoma was shorter compared to patients with a ductal adenocarcinoma after surgical tumor resection. This study suggests that distinct multimodal treatment protocols should be considered for adenosquamous carcinomas of the pancreas. ABSTRACT: Background: Adenosquamous carcinoma of the pancreas (ASCP) is a rare malignancy and its pathophysiology is poorly understood. Sparse clinical data suggest that clinical outcome and overall survival is worse in comparison to common pancreatic ductal adenocarcinoma (PDAC). Methods: We evaluated clinical outcome and prognostic factors for overall survival of patients with ASCP in comparison to patients with PDAC recorded between 2000 and 2019 in 17 population-based clinical cancer registries at certified cancer centers within the Association of German Tumor Centers (ADT). Results: We identified 278 (0.5%) patients with ASCP in the entire cohort of 52,518 patients with pancreatic cancer. Significantly, more patients underwent surgical resection in the cohort of ASCP patients in comparison to patients with PDAC (p < 0.001). In the cohort of 142 surgically resected patients with ASCP, the majority of patients was treated by pancreatoduodenectomy (44.4%). However, compared to the cohort of PDAC patients, significantly more patients underwent distal pancreatectomy (p < 0.001), suggesting that a significantly higher proportion of ASCP tumors was located in the pancreatic body/tail. ASCPs were significantly more often poorly differentiated (G3) (p < 0.001) and blood vessel invasion (V1) was detected more frequently (p = 0.01) in comparison with PDAC. Median overall survival was 6.13 months (95% CI 5.20–7.06) for ASCP and 8.10 months (95% CI 7.93–8.22) for PDAC patients, respectively (p = 0.094). However, when comparing only those patients who underwent surgical resection, overall survival of ASCP patients was significantly shorter (11.80; 95% CI 8.20–15.40 months) compared to PDAC patients (16.17; 95% CI 15.78–16.55 months) (p = 0.007). ASCP was a highly significant prognostic factor for overall survival in univariable regression analysis (p = 0.007) as well as in multivariable Cox regression analysis (HR 1.303; 95% CI 1.013–1.677; p = 0.039). Conclusions: In conclusion, ASCP showed poorer differentiation and higher frequency of blood vessel invasion indicative of a more aggressive tumor biology. ASCP was a significant prognostic factor for overall survival in a multivariable analysis. Overall survival of resected ASCP patients was significantly shorter compared to resected PDAC patients. However, surgical resection still improved survival significantly.