Comparison of the dosimetries of 3-dimensions Radiotherapy (3D-RT) with linear accelerator and intensity modulated radiotherapy (IMRT) with helical tomotherapy in children irradiated for neuroblastoma

Abstract

BackgroundIntensity modulated radiotherapy is an efficient radiotherapy technique to increase dose in target volumes and decrease irradiation dose in organs at risk. This last objective is mainly relevant in children. However, previous results suggested that IMRT could increase low dose, factor of risk for secondary radiation induced cancer. This study was performed to compare dose distributions with 3D-radiotherapy (3D-RT) and IMRT with tomotherapy (HT) in children with neuroblastoma. Seven children with neuroblastoma were irradiated. Treatment plans were calculated for 3D-RT, and for HT. For the volume of interest, the PTV-V95% and conformity index were calculated. Dose constraints of all the organs at risk and integral dose were compared.ResultsThe conformity index was statistically better for HT than for 3D-RT. PTV-V95% constraint was reached in 6 cases with HT compared to 2 cases with 3D-RT. For the ipsilateral kidney of the tumor, the V12 Gy constraint was reached for 3 patients with both methods. The values were lower with HT than with 3D-RT in two cases and higher in one case. The threshold was not reached for one patient with either technique, but the value was lower with HT than with 3D-RT. For the contralateral kidney of the tumors, the V12 Gy constraint was reached for all patients with both methods. The values were lower with HT than with 3D-RT in 5 of 7 children, equal in one patient and higher in one patient. The organ-at-risk volumes receiving low doses were significantly lower with 3D-RT but larger for the highest doses, compared to those irradiated with HT. The integral doses were not different.ConclusionsIMRT with HT allows a better conformity treatment, a more frequently acceptable PTV-V95% than 3D-RT and, concomitantly, a better shielding of the kidneys. The integral doses are comparable between both techniques but consideration of differences in dose distribution between the two techniques, for the organs at risk, has to be taken in account when validating treatment.

Can We Spare the Pancreas and Other Abdominal Organs at Risk? A Comparison of Conformal Radiotherapy, Helical Tomotherapy and Proton Beam Therapy in Pediatric Irradiation

“…To achieve good coverage with CRT, the volume receiving high dose must be large: in our study the conformity index with CRT was approximately twice that with HT and beyond compared to PBT. Other reports have shown similar results [ 12 , 13 , 20 ]. The mean dose received was considerably reduced with HT in the ipsilateral kidney thanks to the reduction of volume that received a high dose.…”

“…In this study on abdominal irradiation, patients were assumed to be of uniform density for integral dose calculation [ 17 ]. The conformity index was calculated using the formula: volume of tissue receiving 95% of the prescribed dose / volume of PTV [ 12 ]. The homogeneity index was calculated using the formula: (D2% PTV–D98% PTV) / D50% PTV; where D2% PTV is the dose received by 2% of the PTV (near-maximum dose), D98% PTV is the dose received by 98% of the PTV (near-minimum dose) and D50% PTV is the median dose to PTV.…”

“…IMRT is commonly used for adult cancers, and its use in pediatric cancer is increasing especially where the PTV has a complex shape, and in neurological and head and neck tumors [ 8 ]. In comparison with conventional IMRT, helical tomotherapy (HT) delivers highly conformal dose distribution potentially to a larger field with a great sparing of OAR [ 10 – 12 ]. However, the benefits of HT over conventional IMRT are still being investigated.…”

Contribution of three-dimensional conformal intensity-modulated radiation therapy for women affected by bulky stage II supradiaphragmatic Hodgkin disease

“…In our series, specially conducted in women, we showed that IMRT was able to significantly avoid large tissue volumes receiving moderate to large doses at the cost of increasing the volume receiving a low dose. However, the integral dose is not increased by the IMRT technique with tomotherapy compared with 3D-CRT, as shown previously [41,75]. …”

Superior sulcus non-small cell lung carcinoma: A comparison of IMRT and 3D-RT dosimetry

“…However, we have already shown that the integral dose was not increased by the use of tomotherapy IMRT. 48,49 In conclusion, our study showed that IMRT is relevant in SS-NSCLC. In patients treated by a curative dose, it leads to a reduction of dose given to critical organs, allowing a better dose distribution in the tumor, and for patients treated with a preoperative schedule, our results provide the opportunity to increase the dose in future controlled trials to improve the pRC.…”