Comparison of 1-, 2-, and 3-Dimensional Tumor Response Assessment After Neoadjuvant GTX-RT in Borderline-Resectable Pancreatic Cancer.

Background: Facilitation of margin-negative resection is the goal of neoadjuvant therapy regimens used in the treatment of borderlineresectable pancreatic cancer patients. Multiple treatment approaches have shown efficacy in this setting, including neoadjuvant GTX (gemcitabine [Gemzar], docetaxel [Taxotere], and capecitabine [Xeloda]) and radiotherapy (RT). Three-dimensional tumor response may be a more accurate method of assessment compared to traditional 1- and 2-dimensional techniques. We compared these 3 methods in a series of patients who underwent neoadjuvant GTX-RT and surgical resection. Materials and Methods: This retrospective review included borderlineresectable pancreatic cancer patients treated with neoadjuvant GTX followed by 5-FU chemoradiotherapy with the intent of downstaging to resectability. Tumor was contoured on computed tomography (CT) scans obtained at the following time points: (A) initial staging, (B) CT simulation, and (C) restaging. These contours were used to determine tumor response according to WHO, RECIST, and volumetric criteria. Results: Fourteen patients all experienced a measurable decrease in tumor volume following neoadjuvant therapy and were deemed suitable for at least surgical exploration. Radiotherapy was delivered to a median 50 Gy (range, 45‐52 Gy) in 1.8‐2.0 Gy fractions via 3-D conformal (21%) or IMRT (79%). The median percent volume changes before and after CT simulation were 3.4% and 52.6%, respectively. The overall median percent change was 54.5%. The corresponding absolute volume changes were 0.42 cm 3 (range, 9.12 to 12.47), 5.31 cm 3 (range, 2.06 to 15.93), and 6.72 cm 3 (range, 0.53 to 15.47), respectively. Response according to WHO, RECIST, and volumetric methods was identical with the exception of 1 patient. Conclusion: This is the first study to quantify volumetric tumor change objectively as a result of neoadjuvant chemoradiotherapy for the treatment of borderline resectable pancreatic cancer. Our data suggest that tumor response to neoadjuvant therapy is essentially equivalent between 1-, 2-, and 3-dimensional assessment methods.