To perform dosimetric analysis of different breast simultaneous-integrated-boost (SIB) irradiation with respect to target coverage and organs at risk (OARs) doses, using volumetric-arc radiotherapy (VMAT) and helical tomotherapy (HT). The dosimetric analysis was performed in 30 early-stage breast cancer patients (15 patents right sided, 15 patients left sided breast) having breast conserving surgery. In SIB plan, the prescribed dose was 64.4 Gy to the PTVboost and 50.4 Gy to the PTVbreast in 28 fractions, and in sequential boost technique (SB) the prescribed dose was 50 Gy to PTVbreast and 16 Gy to PTVbreast delivered in 33 fractions. The target volume and OARs doses, conformity (CI) and homogeneity indices (HI) were compared between SIB and SB plans for both VMAT and HT plans. For SB and SIB plans, the average maximum doses of PTV were significantly higher in VMAT plans than in HT (56.46±2.24 Gy vs. 53.21±0.92; p < 0.001 and 54.24±0.77 Gy vs. 51.80±0.71 Gy; p < 0.001, respectively). The maximum PTV doses were significantly higher in SB plan compared to SIB plan in both VMAT and HT plans. The CI was significantly higher in HT for SB plan (0.67±0.08 vs. 0.63±0.07; p < 0.001), however no significant difference was observed in SIB plan between VMAT and HT (0.67±0.09 vs. 0.65±0.08; p = 0.15). The CI in VMAT plan was better SIB plan compared to SB plan, however no significant difference was observed in HT. The HI was significantly higher in HT compared to VMAT for both SB and SIB plans (0.36±0.03 vs. 0.33±0.02; p = 0.001 and 0.32±0.04 vs. 0.30±0.02; p = 0.006, respectively). Lung V5 was significantly higher in VMAT compared to HT for SB plan (53.67±7.93 Gy vs. 43.73±7.25 Gy; p = 0.02). However, other dosimetric parameters for ipsilateral lung and heart did not differ significantly between each plan for VMAT and HT. The significant dosimetric advantage of contralateral lung V5 was found in HT compared to VMAT for SB plan (1.98±0.73 Gy vs. 3.52±1.40; p = 0.03). Although contralateral lung V5 was significantly lower in SIB plan compared to SB plan for HT (1.98±0.73 Gy vs. 1.61±1.06 Gy; p = 0.003), contralateral lung V5 was significantly higher in SIB plan for VMAT (4.04±3.22 Gy vs. 3.52±1.40 Gy; p = 0.04). Contralateral breast V5 was significantly lower in HT compared to VMAT for SB plan (1.48±1.19 Gy vs. 4.61±3.55 Gy; p = 0.03), however no significant difference was found for SIB plan between HT and VMAT (1.33±0.46 Gy vs. 1.82±0.77; p = 0.64). For breast irradiation after breast conserving surgery, HT is advantageous for lower maximum PTV doses, better conformity, and homogeneity in target volume doses compared to VMAT. Additionally, contralateral breast and lung doses were significantly lower in HT compared to VMAT. With SIB technique the target dose homogeneity and conformity was better, contralateral lung and breast doses were lower compared to SB technique. Our study demonstrated the dosimetric feasibility of SIB using HT for breast cancer patients.

To compare dosimetric data of stereotactic body radiotherapy (SBRT) plans with volumetric-arc therapy (VMAT), helical tomotherapy (HT) and RayStation (RS) for liver metastasis. The dosimetric data of 19 patients with liver metastasis treated with liver SBRT were analyzed. Three different plans were generated with same computed tomography (CT) images. The prescribed dose was 54 Gy delivered in 3 fractions and the dose was prescribed to 90% isodose line. For all patients, cumulative dose–volume histograms and dosimetric parameters were calculated and compared for the planning target volume (PTV) and organs at risk (OAR). D2 and D98 were used as a surrogate for maximum and minimum dose, respectively. D2 and D98 are the minimal doses to 2 % and 98 % of target volume, respectively. The target homogeneity and conformal index values (HI and CI, respectively) are compared. OARs doses, including kidneys, liver, bowel, and spinal cord, were also assessed. All plans meet the criteria for PTV coverage. The average maximum doses for PTV (D2) were significantly higher in VMAT plans compared to HT and RS plans (Table 1). The CI and HI indices were significantly lower in RS plans compared to HT plans and VMAT plans. Similarly CI and HI indices were significantly lower in HT plans compared to VMAT plans. Liver Dmean was significantly higher in RS plan (10.9±4.8 Gy) compared to VMAT plan (9.6±3.8 Gy; p=0.001) and HT plan (10.1±4.4 Gy; p=0.006). However there was no significant difference for Liver Dmean between VMAT and HT plans (p=0.08). The liver V5 to V45 were significantly higher in RS plan compared to VMAT and HT plans (Figure 1). There were no significant difference in liver doses between VMAT plans and HT plans except for V5 (p=0.001) and V10 (p=0.005) values. The Dmean of both kidneys were significantly higher in HT plans (2.4±1.8 Gy) compared to VMAT plans (1.9±1.6 Gy; p=0.005) and RS plans (1.4±0.8 Gy; p=0.004). However there were no significant difference in Dmeanof both kidneys between VMAT and RS plans. For the spinal cord and bowel, maximum doses did not differ significantly between each techniques. The monitor unit for RS plan was significantly less in RS plan compared to VMAT plan (2774±271 vs. 4052±1591; p=0.003). The RS plans reduced the maximum dose applied to the target area, with improved the conformality and homogeneity of radiation. However, the liver does were significantly higher in RS plan compared to HT and VMAT plans.Tabled 1Abstract 2428; Table 1ParametersVMAT(Mean±SD)HT(Mean±SD)RayStation(Mean±SD)p(VMAT vs. HT)p(VMAT vs. RS)p(HT vs. RS)D2% (Gy)57.0±1.055.4±0.354.4±0.3<0.001<0.001<0.001D100% (Gy)52.0±2.352.5±1.052.5±0.80.330.190.73D98% (Gy)54.2±0.753.9±0.253.7±0.20.140.003<0.001D95% (Gy)54.5±0.654.2±0.253.8±0.20.02<0.001<0.001D90% (Gy)54.8±0.654.3±0.253.9±0.20.001<0.001<0.001D50% (Gy)55.8±0.654.8±0.354.1±0.2<0.001<0.001<0.001CI1.53±0.101.52±0.101.51±0.100.020.0030.001HI1.05±0.021.03±0.011.01±0.01<0.001<0.001<0.001 Open table in a new tab

_____________________________________________________________________________________________________lenses, as shown also in the Table.Dose values are smaller (Dmax 16.7%, i.e. around 6 Gy) than those reported in other studies.In our case, the opposed-lateral setup is associated to larger lens doses (56.6%) than those reported using the same technique in another study (26.4%), suggesting that our specific case was a difficult one, presumably age-related. Conclusion:The beam arrangement we applied allowed both an optimal coverage of the cribriform plate and lens sparing.The low maximal dose to the lenses might reduce the risk of radiation-associated cataract.

In this study, we investigated the shrinking effect of concurrent three-dimensional conformal radiotherapy (3D-CRT) and androgen deprivation (AD) on prostate volume, and its possible impact on the dose received by the rectum and bladder during the course of 3D-CRT. The difference between the prostatic volumes determined on pre-treatment planning CT (PL-CT) and post-treatment CT (PT-CT) following a 3D-CRT course was assessed in 52 patients with localised prostate carcinoma. The changes in mean prostate volume when compared with PL-CT and PT-CT-based measurements were assessed. The pre- and post-treatment mean prostate volumes for the whole study population were 49.7 cm(3) and 41.0 cm(3) (p _ 0.02), respectively. The study cohort was divided into two groups depending on the duration of neoadjuvant androgen deprivation (NAD): 23 patients (44.7%) were designated as "short NAD" (< or =3 months; SNAD) and the remaining 29 (55.3%) as "long NAD" (>3 months; LNAD). Patients on SNAD experienced a significantly greater reduction in prostate volume compared with those on LNAD (14.1% vs 5.1%; p _ 0.03). A significant increase in rectum V(40-60) values in PT-CT compared with PL-CT was demonstrated. LNAD patients had significantly higher rectal V(50-70) values at PT-CT compared with the SNAD group. There was a significant decline in V(30)-V(75) bladder values in PT-CT compared with PL-CT in the SNAD group. In conclusion, a higher prostate volume reduction during 3D-CRT was demonstrated when RT planning was performed within 3 months of NAD. However, this reduction and daily organ motion may lead to an unpredictable increase in rectal doses.