Porównanie radioterapii wiązką z modulacją intensywności dawki (IMRT) i konformalnej radioterapii (CFRT) w planowaniu leczenia u chorych na raka trzustki

Abstract

Introduction. Pancreatic cancer is the sixth highest cause of mortality in patients with malignant neoplasms in Poland. The results of treatment are poor and prognosis unfavourable. The basic method of treatment is surgery with adjuvant chemo or radiochemotherapy. Aim. The aim of the study was to compare CFRT (2F, 3F, 4F) and IMRT in planning of adiuvant radiotherapy for fi fteen patients with pancreatic cancer. Material and method. For each patient from this group four treatment plans were performed: three for CFRT and one for IMRT. The CFRT plans consisted of two opposite fi elds (2F), two opposite fi elds and one oblique fi elds (3F), two lateral and two oblique fi elds (4F) and the IMRT plan. The treatment plans were performed to achieve a minimum dose to the PTV which was no lower than 95% of the total prescribed dose. Treatment plans were compared using dose-volume histograms (DVH) and using V20 parameter for left (LK) and right kidney (RK), V30 for liver (L), maximal dose for spinal cord (SC), maximal dose for intestines (IN), mean dose for whole liver and each kidney. The PTC (Percent Target Coverage), CI (Conformity Index) and HI (Homogenity Index) parameters were evaluated for each plan. For the evaluation of statistical signifi cance the nonparametric Wilcoxon’s test was performed. Results. The minimum dose in the PTV (PTVmin) for 2F plan was: 42.8 Gy, 3F — 42.9 Gy, 4F — 43.2 Gy and in IMRT — 43.2 Gy (p = 0.006). The maximal dose for spinal cord was acceptable in all plans (3F — 44 Gy, 4F — 42 Gy, IMRT — 45 Gy) except in 2F — 47.7 Gy (2F vs IMRT p = 0.00065, 3F vs IMRT p = 0.95, 4F vs IMRT p = 0.005). The median volume for each kidney V20 was comparable for all conformal plans. For the left kidney 44.7%, 41%, 40% for 2F, 3F and 4F respectively and 11.3%, 10.7%, 9.2% for the right kidney. The V20 for the left kidney was 18% and 6% for the right kidney using the IMRT plans (p < 0.002). The V30 for the liver was comparable for each of the plans: 2F — 8,3%, 3F — 8%, 4F — 7% and IMRT — 7%. (2F vs IMRT p = 0.015, 3F vs IMRT p = 0.04, 4F vs IMRT p = 0.36). The maximal dose to the intestines was acceptable in all plans 2F — 48.5 Gy, 3F — 47.0 Gy, 4F — 46.7 Gy, IMRT — 48.0 Gy (p = 0.001). Conclusions. Using IMRT in the planning of adjuvant radiotherapy for patients after surgery for pancreatic cancer achieves a better dose distribution and protection of kidneys compared to standard conformal planning. All techniques achieved a similar dose distribution in the liver and intestines.