Purpose This study aimed at evaluating the clinical impact of full intensity-modulated radiotherapy (IMRT), hybrid IMRT (H-IMRT) and hybrid volumetric-modulated arc therapy (H-VMAT) for early-stage breast cancer with simultaneous integrated boost (SIB), in terms of plan quality and second cancer risk (SCR). Methods Three different plans were designed in full IMRT, hybrid IMRT, and hybrid VMAT for each of twenty patients with early-stage breast cancer. Target quality, organs at risk (OARs) sparing, and SCR were compared among the three plans for each case. Results In compared with H-IMRT, IMRT plans showed deterioration in terms of D2% of SIB, V10 of ipsilateral lung, and excess absolute risk (EAR) to contralateral lung (C-Lung) and esophagus. D2% and the homogeneity index (HI) of SIB, V5 of ipsilateral lung (I-Lung), the Dmean of the esophagus, the EAR to C-Lung and the esophagus with hybrid VMAT dramatically increased by 0.63%, 10%, 17.99%, 149.27%, 230.41%, and 135.29%, respectively (p = 0.024; 0.025; 0.046; 0.011; 0.000; 0.014). Dmean of the heart, the EAR to contralateral breast (C-Breast) and C-Lung by full IMRT was significantly decreased in comparison to the H-VMAT (4.67%, p = 0.033, 26.76%, p = 0.018; 48.05%, p = 0.036). Conclusion The results confirmed that H-IMRT could achieve better target quality and OARs sparing than IMRT and H-VMAT for SIB radiotherapy of early-stage right breast cancer. H-IMRT was the best treatment option, while H-VMAT performed the worst among the three plans in terms of SCR to peripheral OARs.
Purpose To evaluate the sensitivity to set up the uncertainty of VMAT plans in Nasopharyngeal carcinoma (NPC) treatment by proposing a plan robustness evaluation method. Methods 10 patients were selected for this study. A 2-arc volumetric-modulated arc therapy (VMAT) plan was generated for each patient using Varian Eclipse (13.6 Version) treatment planning system (TPS). 5 uncertainty plans (U-plans) were recalculated based on the first 5 times set-up errors acquired from cone-beam computer tomography (CBCT). The dose differences of the original plan and perturbed plan corresponded to the plan robustness for the structure. Tumor control probability (TCP) and normal tissues complication probability (NTCP) were calculated for biological evaluation. Results The mean dose differences of D98% and D95% (ΔD98% and ΔD95%) of PTVp were respectively 3.30 Gy and 2.02 Gy. The ΔD98% and ΔD95% of CTVp were 1.12 Gy and 0.58 Gy. The ΔD98% and ΔD95% of CTVn were 1.39 Gy and 1.03 Gy, distinctively lower than those in PTVn (2.8 Gy and 2.0 Gy). The CTV-to-PTV margin increased the robustness of CTVs. The ΔD98% and ΔD95% of GTVp were 0.56 Gy and 0.33 Gy. GTVn exhibited strong robustness with little variation of D98% (0.64 Gy) and D95% (0.39 Gy). No marked mean dose variations of Dmean were seen. The mean reduction of TCP (ΔTCP) in GTVp and CTVp were respectively 0.4% and 0.3%. The mean ΔTCPs of GTVn and CTVn were 0.92% and 1.3% respectively. The CTV exhibited the largest ΔTCP (2.2%). In OARs, the brain stem exhibited weak robustness due to their locations in the vicinity of PTV. Bilateral parotid glands were sensitive to set-up uncertainty with a mean reduction of NTCP (ΔNTCP) of 6.17% (left) and 7.70% (right). The Dmax of optical nerves and lens varied slightly. Conclusion VMAT plans had a strong sensitivity to set-up uncertainty in NPC radiotherapy, with increasing risk of underdose of tumor and overdose of vicinal OARs. We proposed an effective method to evaluate the plan robustness of VMAT plans. Plan robustness and complexity should be taken into account in photon radiotherapy.
Purpose This study aimed to evaluate the clinical impact of hybrid intensity-modulated radiotherapy (IMRT) and hybrid volumetric-modulated arc therapy (VMAT) for early-stage breast cancer, including plan quality and second cancer risk (SCR). Methods Three different plans were designed in full IMRT, hybrid IMRT, and hybrid VMAT for each of eight patients with early-stage breast cancer. Target quality, organs at risk (OARs) sparing, and SCR were compared among the three plans. Results Compared with the hybrid IMRT, full IMRT showed deterioration in terms of D2% of simultaneous integrated boost (SIB), V10 of ipsilateral lung, and excess absolute risk (EAR) to contralateral lung and esophagus. The homogeneity index (HI) of SIB, V5 of ipsilateral lung and combined lung, the Dmax and Dmean of the esophagus, the EAR to contralateral breast and lung, and the EAR to the esophagus with hybrid VMAT dramatically increased by 12.5%, 19.49%, 18.87%, 90.59%, 167.69%, 50.14%, 264.68%, and 160.95%, respectively (p = 0.022; 0.040; 0.044; 0.041; 0.003; 0.020; 0.000; 0.003). The EAR to contralateral breast and contralateral lung by full IMRT was significantly decreased compared with the hybrid VMAT (26.97%, p = 0.033; 50.01%, p = 0.026). Conclusion The results confirmed that hybrid IMRT could achieve better target quality and OARs sparing than full IMRT and hybrid VMAT for early-stage right breast cancer. Hybrid IMRT was the best treatment option, while hybrid VMAT performed the worst among the three plans in terms of SCR to peripheral OARs.
To compare the dosimetric effects of American Association of Physicists in Medicine (AAPM) TG43 dose formalism and AcurosBV ( grid-based Boltzmann solver ,GBBS) formalism on High-dose-rate(HDR) brachytherapy planning for cervical cancer patients irradiated using three different applicators. MethodsA TG43 plan and a AcurosBV plan were generated for each of the 30 patients. twenty patients who had undergone whole pelvic radiotherapy followed by cervical HDR brachytherapy and the remaining 10 patients who underwent total hysterectomy only gave HDR brachytherapy also were enrolled in this study. The patients were divided into three groups according to the types of applicators used: tandem and ovoid (T&O), tandem and ring (T&R), and Cylinder. To compare the dosimetric parameters, the cumulative dosevolume histograms (DVHs) were measured. We also compared the doses at 90% of the volume (D 90% ), the volume receiving 100% and 150% of the prescribed dose (V 100% and V 150% ) for the clinical target volume (CTV-HR) and the doses of point A, the dose receiving 0.1 cc and 2 cc of the volume (D 0.1cc and D 2cc ) for the organs-at-risk (OARs). ResultsIn this study, compared with the AcurosBV plans, TG43 plans predicted higher D 90% , V 100% , and V 150% of CTV-HR, dose of point A and D 0.1cc and D 2cc of OARs in three types of applicators. Except D 2cc of sigmoid in T&R and Cylinder applicators, the D 90% , V 100% , and V 150% of CTV-HR; the Dose of point A and the D 0.1cc and D 2cc of bladder, recutum and small bowel exhibited signi cant discrepancies (P > 0.05). The effects of the three types of applicators on the dose distribution were quite different due to the difference of the materials: The dose difference of CTV-HR and OARs was greatest (around 10%) for T&O applicators but only 1%-5% for T&R and Cylinder applicators. ConclusionsThis study demonstrated that AcurosBV was more accurate in calculating the doses in the air cavity and high-density substance than TG43. In the clinical setting, the AcurosBV exhibited different dosimetric distributions in the cervix plans for HDR brachytherapy, especially in treatment planning when using T&O applicators. The AcurosBV algorithm should be considered when using T&O applicators or some other materials with a much higher or lower density (metal or air) than soft tissue. Howevere, If the density is close to the soft tissue, considering AcurosBV algorithm requires more calculation time, TG43 could still be selected when using applicators in clinical.
Purpose: To compare the dosimetric effects of American Association of Physicists in Medicine (AAPM) TG43 dose formalism and AcurosBV ( grid-based Boltzmann solver ,GBBS) formalism on High-dose-rate(HDR) brachytherapy planning for cervical cancer patients irradiated using three different applicators.Methods: A TG43 plan and a AcurosBV plan were generated for each of the 30 patients. twenty patients who had undergone whole pelvic radiotherapy followed by cervical HDR brachytherapy and the remaining 10 patients who underwent total hysterectomy only gave HDR brachytherapy also were enrolled in this study. The patients were divided into three groups according to the types of applicators used: tandem and ovoid (T&O), tandem and ring (T&R), and Cylinder. To compare the dosimetric parameters, the cumulative dose-volume histograms (DVHs) were measured. We also compared the doses at 90% of the volume (D90%) , the volume receiving 100% and 150% of the prescribed dose (V100% and V150%) for the clinical target volume (CTV-HR) and the doses of point A, the dose receiving 0.1 cc and 2 cc of the volume (D0.1cc and D2cc) for the organs-at-risk (OARs).Results: In this study, compared with the AcurosBV plans, TG43 plans predicted higher D90%, V100%, and V150% of CTV-HR, dose of point A and D0.1cc and D2cc of OARs in three types of applicators. Except D2cc of sigmoid in T&R and Cylinder applicators, the D90%, V100%, and V150% of CTV-HR; the Dose of point A and the D0.1cc and D2cc of bladder, recutum and small bowel exhibited significant discrepancies (P>0.05). The effects of the three types of applicators on the dose distribution were quite different due to the difference of the materials: The dose difference of CTV-HR and OARs was greatest (around 10%) for T&O applicators but only 1%-5% for T&R and Cylinder applicators.Conclusions: This study demonstrated that AcurosBV was more accurate in calculating the doses in the air cavity and high-density substance than TG43. In the clinical setting, the AcurosBV exhibited different dosimetric distributions in the cervix plans for HDR brachytherapy, especially in treatment planning when using T&O applicators. The AcurosBV algorithm should be considered when using T&O applicators or some other materials with a much higher or lower density (metal or air) than soft tissue. Howevere, If the density is close to the soft tissue, considering AcurosBV algorithm requires more calculation time, TG43 could still be selected when using applicators in clinical.
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