Prognostic significance of pancreatic tumor regression after intraoperative radiotherapy.

Tumor volume measurement using tumor-margin clipping radiography was performed for estimating tumor regression of eight pancreatic adenocarcinomas treated with intraoperative electron irradiation. Half of the tumors regressed exponentially from the first day of treatment, but the other half increased slightly within the first week, after which volume reduction occurred. The volume-halving time was calculated from the regression curve. A wide distribution of volume-halving times as well as initial tumor volumes was seen in all patients. No correlation was found between these variables, but the former correlated well with survival time (r2 = 0.80). This well-known technique may offer a chance to foresee the prognosis of the disease by determining the volume-halving time.