Oncologic outcomes and prognostic factors of colloid carcinoma of the pancreas - a retrospective real-world data analysis from the German cancer registry group of the society of German tumor centers.

Background: Colloid carcinoma (CC) is a rare subtype of pancreatic ductal adenocarcinoma (PDAC) characterized by mucin pools in over 80% of the tumor. This study compares the histopathology and outcomes of CC and not-otherwise specified PDAC (PDAC-NOS, referring to "classical" PDAC) using pooled data retrieved from regional cancer registries participating in the Clinical Cancer Registry Group of the Association of German Tumor Centers (GCRG/ADT).

Materials and methods: Data from patients within the pooled dataset of the GCRG/ADT with pancreatic cancer (diagnosed between 2000 and 2023) were analyzed. Histological subtypes were identified by ICD-O3 histology code. Epidemiology, histopathology and survival rates were compared between surgically resected CC and PDAC-NOS. Prognostic impacts were assessed using uni- and multivariable regression analyses in R.

Results: The study included 474 CC and 21,360 PDAC-NOS patients. CC patients presented more often without lymph node metastases (pN0: 44.0 vs. 31.5%, p < 0.001), lower grading and less lymphatic and blood vessel invasion (each p < 0.001). The R0 resection rate was similar in both groups. CC patients had superior OS compared to PDAC-NOS (median OS: 24.8 vs. 17.3 months, p < 0.001). Importantly, CC histology was an independent positive prognostic factor for OS. Grading, lymph- and blood-vessel invasion were independent prognostic factors for CC patients. Adjuvant therapy was associated with improved survival in UICC IIB CC patients.

Conclusion: CC patients showed better oncological outcomes after surgical resection compared to PDAC-NOS. Thereby, CC-subtype is an independent positive prognostic factor for OS, associated with lower tumor stages, fewer lymph node metastases, and less vascular invasion.