Dosimetric and Clinical Toxicity Comparison of Critical Organ Preservation with Three-Dimensional Conformal Radiotherapy, Intensity-Modulated Radiotherapy, and RapidArc for the Treatment of Locally Advanced Cancer of the Pancreatic Head

Purpose: We compared dosimetry and clinical toxicity for 3-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT), and RapidArc (Varian Medical Systems, Palo Alto, CA, U.S.A.) in locally advanced pancreatic cancer (LAPCC). We hypothesized that the technique with better sparing of organs at risk (OARs) and better target dose distributions could lead to decreased clinical toxicity. Methods: The study analyzed 280 patients with LAPCC who had undergone radiotherapy. The dosimetry comparison was performed using 20 of those patients. Dose–volume histograms for the target volume and the OARs were compared. The clinical toxicity comparison used the 280 patients who received radiation with 3D-CRT, IMRT, or RapidArc. Compared with 3D-CRT, RapidArc and IMRT both achieved a better conformal index, homogeneity index, V_95%, and V_110%. Results: Compared with 3D-CRT or IMRT, RapidArc reduced the V₁₀, V₂₀, and mean dose to duodenum, the V₂₀ of the right kidney, and the liver mean dose. Compared with 3D-CRT, RapidArc reduced the V₃₅, and V₄₅ of duodenum, the mean dose to small bowel, and the V₁₅ of right kidney. The incidences of grades 3 and 4 diarrhea (p = 0.037) and anorexia (p = 0.042) were lower with RapidArc than with 3D-CRT, and the incidences of grades 3 and 4 diarrhea (p = 0.027) were lower with RapidArc than with IMRT. Conclusions: Compared with 3D-CRT or IMRT, RapidArc showed better sparing of OARs, especially duodenum, small bowel, and right kidney. Also, fewer acute grades 3 and 4 gastrointestinal toxicities were seen with RapidArc than with 3D-CRT or IMRT. A technique with better sparing of OARs and better target dose distributions could result in decreased clinical toxicities during radiation treatment for LAPCC.