Abstract
PurposeTo investigate the potential clinical benefits of using stereotactic body radiation therapy (SBRT) with simultaneous integrated boost (SIB) technique for locally advanced pancreatic cancer (LAPC) among different treatment modalities and planning strategies, including photon and proton.MethodA total of 19 patients were retrospectively selected in this study: 13 cases with the tumor located in the head of the pancreas and 6 cases with the tumor in the body of the pancreas. SBRT-SIB plans were generated using volumetric modulated arc therapy (VMAT), two-field Intensity Modulated Proton Therapy (IMPT), and three-field IMPT. The IMPT used the robust optimization parameters of ± 3.5% range and 5-mm setup uncertainties. Root-mean-square deviation dose (RMSD) volume histograms were used to evaluate the target coverage robustness quantitatively. Dosimetric metrics based on the dose-volume histogram (DVH), homogeneity index (HI), and normal tissue complication probability (NTCP) were analyzed to evaluate the potential clinical benefits among different planning groups.ResultsWith a similar CTV and SIB coverage, two-field IMPT provided a lower maximum dose for the stomach (median: 18.6GyE, p<0.05) and duodenum (median: 32.62GyE, p<0.05) when the target was located in the head of the pancreas compared to VMAT and three-field IMPT. The risks of gastric bleed (3.42%) and grade ≥ 3 GI toxicity (4.55%) were also decreased. However, for the target in the body of the pancreas, VMAT showed a lower maximum dose for the stomach (median 30.93GyE, p<0.05) and toxicity of gastric bleed (median: 8.67%, p<0.05) compared to two-field IMPT and three-field IMPT, while other maximum doses and NTCPs were similar. The RMSD volume histogram (RVH) analysis shows that three-field IMPT provided better robustness for targets but not for OARs. Instead, three-field IMPT increased the Dmean of organs such as the stomach, duodenum, and intestine.ConclusionThe results indicated that the tumor locations could play a critical role in determining clinical benefits among different treatment modalities. Two-field IMPT could be a better option for LAPC patients whose tumors are located in the head of the pancreas. It provides lower severe toxicity for the stomach and duodenum. Nevertheless, VMAT is preferred for the body with better protection for the possibility of gastric bleed.
Highlights
Pancreatic cancer is a malignant tumor with a high mortality rate
For the locally advanced pancreatic cancer (LAPC) patient population, stereotactic body radiation therapy (SBRT) is the first-line treatment recommended by the guidelines, providing better survival than chemotherapy alone or conventional-fraction radiation therapy (CFRT) [4,5,6]
The same HI value of the boost area was obtained for tumors located in the body of the pancreas compared to twofield intensity-modulated proton therapy (IMPT) and three-field IMPT
Summary
Pancreatic cancer is a malignant tumor with a high mortality rate. It is the sixth leading cause of cancer death in China and the fourth leading cause of cancer death in the United States [1, 2]. For the locally advanced pancreatic cancer (LAPC) patient population, stereotactic body radiation therapy (SBRT) is the first-line treatment recommended by the guidelines, providing better survival than chemotherapy alone or conventional-fraction radiation therapy (CFRT) [4,5,6]. A stage I clinical trial proved the safety of delivering 36 Gy in three fractions to borderline resectable pancreatic cancer (BRPC), with a 9-Gy SIB to the positive posterior margins (PM) in patients whose tumor was at least 3 mm away from the duodenum [8]. Surpassing dose tolerance to these structures could cause gastrointestinal perforation or ulceration, which could be fatal
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