Statistically significant correlation was similarly observed in variation between day 29pre serum sCD26/DPP4 titer and tumor volume, and between pre and/or post day 29 serum sCD26/DPP4 titer and PFS in 18 cases with Q2W administration frequency and 14 male cases with Q2W administration frequency (Additional file 4 (Table S3) and file 5 (Table S4)). The gene discussed is DPP4; the disease is neoplasm.