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Assessment of different methods of boost delivery (IMRT vs. 3-D conformal) on target coverage and normal tissue sparing

2001; Elsevier BV; Volume: 51; Issue: 3 Linguagem: Inglês

10.1016/s0360-3016(01)02550-0

1879-355X

N. Dogan, Stephanie King, Najeeb Mohideen, L. Leybovich, Nena Mirković, Anil Sethi, Bahman Emami,

Radiomics and Machine Learning in Medical Imaging

Purpose: Due to biological, medical,and sometimes logistic reasons, patients may be treated with 3-D Conformal Therapy(3-D CRT) to the initial treatment volume(CTV1) followed by a boost dose delivered to CTV2(boost volume) by 3-D CRT or Intensity Modulated Radiation Therapy(IMRT). In some patients, CTV1 and CTV2 may be treated by IMRT all the way. Purpose of this work was to assess the three methods of dose delivery on target coverage and normal tissue sparing.Materials and methods: Fifteen patients with head and neck, lung, and prostate cancers were selected for this comparative study. Each site included five patients. In all patients, target consisted of CTV1 and CTV2. Prescription doses to CTV1 and CTV2 were: 46Gy and 66Gy (head and neck cases),45Gy and 66.6Gy(lung cases), 50–54Gy and 76–78Gy (prostate). Critical structures included: cord, parotids, and brainstem(head and neck); cord, esophagus, lungs, heart(lung); bladder, rectum, femurs(prostate). Both 3-D CRT and IMRT plans were created using FOCUS Planning System. Beam arrangements used in 3-D CRT plans were patient specific. For all cases, step-and-shoot IMRT plans consisted of 7-nonopposed coplanar beams. Plans were compared using dose delivered to 95% of target volume (TD95%), mean critical structure dose (Dmean), and maximum critical structure dose (Dmax).Results: Head and Neck Cases: Average TD95% for CTV1 and CTV2 was 47.7Gy and 66.6Gy(boost by 3-D CRT) vs. 46.3Gy and 64.2Gy(boost by IMRT) vs. 51.5Gy and 68.4Gy(IMRT all the way). Average brainstem Dmax and Dmean was 48.8Gy and 14.7Gy(boost by 3-D CRT) vs. 45.2Gy and 14.9Gy(boost by IMRT) vs. 43.7Gy and 16.9Gy(IMRT all the way). For cord, average Dmax and Dmean were 44.7Gy and 33Gy (boost by 3-D CRT). Boost by IMRT method reduced Dmean for cord to 30Gy. Further reductions achieved in cord Dmean(23Gy) using IMRT all the way. Significant reduction in mean parotid doses(∼30%) was observed using IMRT all the way compared to boost by 3-D CRT. Average parotid doses were reduced ∼9% using boost by IMRT compared to boost by 3-D CRT.Lung Cases: For all techniques, average TD95% for CTV1(∼50Gy) and CTV2(∼65Gy) was very similar. For cord, although average Dmax was similar(∼44Gy) in all methods, Dmean was reduced to 11Gy with IMRT all the way from 16Gy with boost by 3-D CRT. Mean cord dose using boost by IMRT was same as boost by 3-DCRT. For lung, IMRT all the way reduced average Dmean to ∼12Gy from ∼16Gy (for both boost by 3-D CRT and boost by IMRT). Similarly, average Dmean to heart was reduced to ∼6Gy (IMRT all the way) from ∼10 Gy (both boost by 3-D CRT and IMRT). Average Dmax for heart was also much lower with IMRT all the way(39Gy) and boost by IMRT(41Gy) as compared to boost by 3-D CRT(47Gy).Average Dmean to esophagus was also reduced ∼10% using IMRT all the way as compared to boost by IMRT and boost by 3-D CRT.Prostate Cases: Average TD95% for CTV1 and CTV2 were 58.9Gy and 74.2Gy(boost by 3-D CRT) vs. 51.1Gy and 61Gy(boost by IMRT) vs. 59.3Gy and 73.3Gy(IMRT all the way). Average Dmean for both bladder and rectum was 5% lower when IMRT all the way as compared to two other boost techniques. Significant reduction in femoral head doses was observed using both boost by IMRT and IMRT all the way techniques. As compared to boost by 3-D CRT, average Dmean for femoral heads was reduced by ∼20% (boost by IMRT) and ∼50%(IMRT all the way).Conclusions: For most patients, the target coverage was adequate for all methods of boost delivery. Boost by IMRT demonstrated moderately improved sparing of the critical structures. Compared to boost by 3-D CRT and IMRT techniques, IMRT all the way markedly reduced doses to the critical structures for all cases considered in this study. Compared to other two techniques, IMRT all the way may have a potential of reducing the total number of fractions. Purpose: Due to biological, medical,and sometimes logistic reasons, patients may be treated with 3-D Conformal Therapy(3-D CRT) to the initial treatment volume(CTV1) followed by a boost dose delivered to CTV2(boost volume) by 3-D CRT or Intensity Modulated Radiation Therapy(IMRT). In some patients, CTV1 and CTV2 may be treated by IMRT all the way. Purpose of this work was to assess the three methods of dose delivery on target coverage and normal tissue sparing. Materials and methods: Fifteen patients with head and neck, lung, and prostate cancers were selected for this comparative study. Each site included five patients. In all patients, target consisted of CTV1 and CTV2. Prescription doses to CTV1 and CTV2 were: 46Gy and 66Gy (head and neck cases),45Gy and 66.6Gy(lung cases), 50–54Gy and 76–78Gy (prostate). Critical structures included: cord, parotids, and brainstem(head and neck); cord, esophagus, lungs, heart(lung); bladder, rectum, femurs(prostate). Both 3-D CRT and IMRT plans were created using FOCUS Planning System. Beam arrangements used in 3-D CRT plans were patient specific. For all cases, step-and-shoot IMRT plans consisted of 7-nonopposed coplanar beams. Plans were compared using dose delivered to 95% of target volume (TD95%), mean critical structure dose (Dmean), and maximum critical structure dose (Dmax). Results: Head and Neck Cases: Average TD95% for CTV1 and CTV2 was 47.7Gy and 66.6Gy(boost by 3-D CRT) vs. 46.3Gy and 64.2Gy(boost by IMRT) vs. 51.5Gy and 68.4Gy(IMRT all the way). Average brainstem Dmax and Dmean was 48.8Gy and 14.7Gy(boost by 3-D CRT) vs. 45.2Gy and 14.9Gy(boost by IMRT) vs. 43.7Gy and 16.9Gy(IMRT all the way). For cord, average Dmax and Dmean were 44.7Gy and 33Gy (boost by 3-D CRT). Boost by IMRT method reduced Dmean for cord to 30Gy. Further reductions achieved in cord Dmean(23Gy) using IMRT all the way. Significant reduction in mean parotid doses(∼30%) was observed using IMRT all the way compared to boost by 3-D CRT. Average parotid doses were reduced ∼9% using boost by IMRT compared to boost by 3-D CRT. Lung Cases: For all techniques, average TD95% for CTV1(∼50Gy) and CTV2(∼65Gy) was very similar. For cord, although average Dmax was similar(∼44Gy) in all methods, Dmean was reduced to 11Gy with IMRT all the way from 16Gy with boost by 3-D CRT. Mean cord dose using boost by IMRT was same as boost by 3-DCRT. For lung, IMRT all the way reduced average Dmean to ∼12Gy from ∼16Gy (for both boost by 3-D CRT and boost by IMRT). Similarly, average Dmean to heart was reduced to ∼6Gy (IMRT all the way) from ∼10 Gy (both boost by 3-D CRT and IMRT). Average Dmax for heart was also much lower with IMRT all the way(39Gy) and boost by IMRT(41Gy) as compared to boost by 3-D CRT(47Gy).Average Dmean to esophagus was also reduced ∼10% using IMRT all the way as compared to boost by IMRT and boost by 3-D CRT. Prostate Cases: Average TD95% for CTV1 and CTV2 were 58.9Gy and 74.2Gy(boost by 3-D CRT) vs. 51.1Gy and 61Gy(boost by IMRT) vs. 59.3Gy and 73.3Gy(IMRT all the way). Average Dmean for both bladder and rectum was 5% lower when IMRT all the way as compared to two other boost techniques. Significant reduction in femoral head doses was observed using both boost by IMRT and IMRT all the way techniques. As compared to boost by 3-D CRT, average Dmean for femoral heads was reduced by ∼20% (boost by IMRT) and ∼50%(IMRT all the way). Conclusions: For most patients, the target coverage was adequate for all methods of boost delivery. Boost by IMRT demonstrated moderately improved sparing of the critical structures. Compared to boost by 3-D CRT and IMRT techniques, IMRT all the way markedly reduced doses to the critical structures for all cases considered in this study. Compared to other two techniques, IMRT all the way may have a potential of reducing the total number of fractions.