Fibroblast-associated protein (FAP) as immunohistochemical prognostic marker after neoadjuvant therapy in Pancreatic Carcinoma – an exploratory study

Purpose Induction chemotherapy is a rather new approach for therapy of Pancreatic adenocarcinoma (PDAC), enabling secondary resectability and an R0-resection as only curative approach to this highly lethal disease. However, chemotherapy-response varies greatly between individuals and is difficult to evaluate by conventional imaging. Molecules within PDACs extensive stroma, such as Fibroblast activation protein (FAP), offer the possibility of molecular markers for evaluation of chemotherapy response. Methods All patients enrolled in our retrospective study underwent surgical tumor resection with one cohort undergoing induction chemotherapy (ICTx) and a matched cohort undergoing upfront resection (US). Survival data derived from the surgical database of Heidelberg University Hospital were compared with histopathological data and FAP immunohistochemistry of tumor tissue derived during resection. Results The ICTx-cohort showed a lower FAP-Expression than the US-cohort and our results indicated a higher stromal component within the ICTx-cohort. Whilst within US no correlation between FAP-expression and stromal component could be made, within ICTx higher FAP levels correlated with a smaller stromal component. FAP-dependent survival also differed between the cohorts: Within US higher FAP levels were associated with shorter survival, while ICTx showed higher FAP levels correlating with improved survival. Conclusion Our results indicate that FAP may be a relevant marker for response to induction chemotherapy in PDAC. It may give significant information on patient survival, depending on clinical context. These preliminary findings need to be confirmed in larger studies.