IMRT, by breaking the large radiation ports used in conventional and 3D conformal radiation therapy into a number of smaller field segments or pencil beams, improves the conformality of a computed radiation dose distribution to the outline of a target volume. No randomized studies have been performed in pancreatic cancer and only one adjuvant study has been performed.
Landry, et al. randomly selected 10 patients with adenocarcinoma of the pancreatic head to undergo simultaneous planning with 3D conformal EBRT and inverse-planned IMRT. The aim of this simulation was to deliver 61.2 Gy to the gross tumor volume (GTV). In this study, the average dose delivered to one-third of the small bowel was significantly lower with the IMRT plan compared with 3D conformal EBRT (P = 0.006). Additionally, the median volume of small bowel that received significantly greater than either 50 or 60 Gy was reduced with IMRT (P = 0.048 and P = 0.034, respectively). Using a normal-tissue complication probability model, the risk of small-bowel complications was 9.3% with IMRT compared with 24.4% with 3D conformal EBRT (P = 0.021). The authors concluded that IMRT with inverse treatment planning can significantly improve radiation to the pancreas by reducing normal tissue dose while allowing for dose escalation to further enhance locoregional control. A cohort of 25 patients treated by IMRT in combination with various chemotherapy regimens was reported by investigators from the University of Texas at San Antonio. In this study, 76% of patients experienced Grade 2 or less toxicity following administration of median doses of 60 Gy.86 At a median follow up of 20 months, 14 of 25 patients treated were alive.
Another recent study evaluated the use of IMRT with concurrent capecitabine. Seven patients received it as adjuvant therapy following curative resection, and eight patients were treated for unresectable disease. Treatment was tolerated well. Only one patient (7%) developed Grade 3 toxicity, and with a median follow- up of 8.5 months, there had been no deaths in the resectable group and only one (14%) local recurrence.
Yang, Gary Y., Wagner, Timothy D., Fuss, Martin, Thomas, Charles R., Jr. Multimodality Approaches for Pancreatic Cancer CA Cancer J Clin 2005 55: 352-367
Landry JC, Yang GY, Ting JY, et al. Treatment of pancreatic cancer tumors with intensity modulated radiation therapy (IMRT) using the volume at risk approach (VARA): employing dose-volume histogram (DVH) and normal tissue complication probability (NTCP) to evaluate small bowel toxicity. Med Dosimetry 2002; 27: 121–129.
Ben-Josef E, Shields A, Vayshampayan U, et al. Intensity-modulated radiotherapy (IMRT) and concurrent capecitabine for pancreatic cancer. Int J Radiat Oncol Biol Phys 2004; 59: 454–459.