ACTN4 copy number increase as a predictive biomarker for chemoradiotherapy of locally advanced pancreatic cancer

Background: Several clinical trials have compared chemotherapy alone and chemoradiotherapy (CRT) for locally advanced pancreatic cancer (LAPC) treatment. However, predictive biomarkers for optimal therapy of LAPC remain to be identified. We retrospectively estimated amplification of the ACTN4 gene to determine its usefulness as a predictive biomarker for LAPC. Methods: The copy number of ACTN4 in 91 biopsy specimens of LAPC before treatment was evaluated using fluorescence in situ hybridisation (FISH). Results: There were no statistically significant differences in overall survival (OS) or progression-free survival (PFS) of LAPC between patients treated with chemotherapy alone or with CRT. In a subgroup analysis of patients treated with CRT, patients with a copy number increase (CNI) of ACTN4 had a worse prognosis of OS than those with a normal copy number (NCN) of ACTN4 (P = 0.0005, log-rank test). However, OS in the subgroup treated with chemotherapy alone was not significantly different between patients with a CNI and a NCN of ACTN4. In the patients with a NCN of ACTN4, the median survival time of PFS in CRT-treated patients was longer than that of patients treated with chemotherapy alone (P = 0.049). Conclusions: The copy number of ACTN4 is a predictive biomarker for CRT of LAPC.