mRNA Expression of Platelet-Derived Growth Factor Receptor-β and C-KIT: Correlation With Pathologic Response to Cetuximab-Based Chemoradiotherapy in Patients With Rectal Cancer

Purpose Deviant expression of platelet-derived growth factor receptor-β (PDGFRβ) and c-kit was shown in patients with colorectal cancer. In the present study, mRNA expression of PDGFRβ and c-kit in 33 patients with locally advanced rectal cancer undergoing preoperative chemoradiotherapy with cetuximab/capecitabine/irinotecan in correlation with the tumor regression rate was investigated. Methods and Materials Pretherapeutic biopsy cores and tumor material from the resected specimens were collected in parallel with normal rectal mucosa. The expression levels of PDGFRβ and c-kit were measured by quantitative polymerase chain reaction. Tumors were classified as good responders (tumor regression grade [TRG], 2-3) or poor responders (TRG, 0-1). Results The TRG evaluation of the resected specimen was TRG 0-1 in 11 and TRG 2-3 in 22. The median normalized ratios in the pretreatment mucosa vs. tumor biopsy cores was as follows: PDGFRβ ratio of 15.2 vs. 49.5 ( p