LAUSR

BACKGROUND Treatment of locally advanced pancreatic cancer (LAPC) has long been calling for advances in technology of radiotherapy. Patients who received radiotherapy still had high risks of local recurrence, while suffering from gastrointestinal side effects. Based on the inherent characteristics of the X-Ray and γ-Ray radiation techniques, here we proposed and investigated an unexplored radiation therapy. PURPOSE To investigate the potential clinical benefit of a novel X-Ray and γ-Ray combination radiation technique in patients with LAPC. METHODS Retrospective intensity-modulated radiotherapy (IMRT) treatment plans of 10 LAPC patients were randomly selected to compare with dual-modality plans. The prescribed dose to PGTV was 60.2 Gy. The PGTV dose was further escalated in dual-modality plan while maintaining clinically tolerable dose to organs at risk (OARs). Dosimetric comparisons were made and analyzed for three treatment plans (tomotherapy, standard dual-modality plan, escalated dual-modality plan) to assess the ability to increase dose to target volume while minimizing dose in adjacent OARs. Finally, radiobiological models were utilized for comparison. RESULTS All strategies resulted in dosimetrically acceptable plans. Dual-modality plans were present with similar conformity index (CI) and significantly lower gradient index (GI) compared with tomotherapy (3.64±0.37 vs. 4.14±0.61, p = 0.002; 3.64±0.42 vs. 4.14±0.61, p = 0.003). Dmean of PGTV (65.46±3.13 vs. 61.56±1.00, p = 0.009; 77.98±5.86 vs. 61.56±1.00, p<0.001) and PCTV (55.04±2.14 vs. 53.93±1.67, p = 0.016; 58.24±3.24 vs. 53.93±1.67, p = 0.001) were significantly higher, while Dmean of the stomach was reduced in both dual-modality plans (17.98±10.23 vs. 19.34±9.75, p = 0.024; 17.62±9.92 vs. 19.34±9.75, p = 0.040). The lower V30Gy in liver (4.83±5.87 vs. 6.23±6.68, p = 0.015; 4.90±5.93 vs. 6.23±6.68, p = 0.016) and lower V45Gy of small intestine (3.35±3.30 vs. 4.06±3.87, p = 0.052) were found in dual-modality plans. Meanwhile, radiobiological models demonstrated higher probability of tumor control ((29.27±9.61)% vs. (18.34±4.70)%, p<0.001; (44.67±18.16)% vs. (18.34±4.70)%, p = 0.001) and lower probability of small intestine complication ((2.16±2.30)% vs. (1.25±2.72)%, p = 0.048) in favor of dual-modality strategy. CONCLUSIONS A novel dual-modality strategy of X-ray and γ-Ray combination radiation appears reliable for target dose escalation and normal tissue dose reduction. This strategy might be beneficial for local tumor control and protection of normal organs in patients with LAPC. This article is protected by copyright. All rights reserved.