Intensity-modulated Radiotherapy Technique Research Articles

Dosimetric effect of modelling non-homogeneous LINAC couch using cone-beam computed tomography on quality assurance (QA) results

Abstract Aim: To evaluate the dosimetric effect of modelling a non-homogeneous couch on patients’ quality assurance (QA) gamma pass rates for intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques. Materials and Methods: A non-homogeneous treatment couch (TxT 550 TTM, CIVCO, USA) was imaged using the LINAC mounted cone-beam computer tomography (CBCT) system. Modelling this couch in different situations, including incomplete (homogeneous model), correct model and not defined situations in the treatment planning system (TPS), was performed based on the geometrical and material densities data extracted from the CBCT images. Calculated gamma pass rates between TPS dose calculations and the measurements in a phantom for different couch models were obtained and compared at two gamma criteria (2%-2 mm and 3%-3 mm). Results: Comparing TPS calculations for the correct modelled couch and the measurements showed high gamma pass rates for both the IMRT and VMAT techniques (96·5 ± 0·9%, 99·2 ± 0·5% for IMRT in 2%-2 mm and 3%-3 mm criteria; 97·5 ± 0·8%, 99·4 ± 0·5% for VMAT). The overall gamma pass rate of the IMRT plan QAs was reduced by about 2% and 3% on average for incomplete and no couch modelling, respectively. These reductions for VMAT techniques were 2·5% and 4·3%, respectively. Conclusions: Non-homogeneous couches have different parts with different attenuations, which can be correctly defined using LINAC CBCT. Modelling of treatment couch has a significant effect on patient QA results for VMAT and IMRT plans, especially in radiation fields/subfield transmitting from the couch. We suggest using LINAC CBCTs as an appropriate device for couch modelling in modulated radiotherapy techniques.

Indian Data on the Response of Positive Pelvic Lymph Nodes in Carcinoma Cervix Patients Treated with Simultaneous Integrated Boost Using Volumetric Modulated Arc Radiation Therapy

Abstract Background The percentage of pelvic lymph node (LN) positivity in cervical cancer patients varies from 19% in early stages to 68% in advanced cases. Thirty-three percent of patients will develop recurrence within 2 years following therapy, and 5-year relative survival for patients with affected regional LNs is 57%. Hence, pelvic LNs need to be included in the definitive plan of radiation treatment for better disease control and longer survival. With conventional radiation therapy, dose escalation was not possible because of small bowel constraints. With higher conformity of intensity-modulated radiotherapy technique, doses to pelvic and abdominal organs can be minimized. The added advantage of simultaneous integrated boost (SIB) is that high dose per fraction is delivered to the gross disease and low dose to the microscopic disease, thereby reducing the total treatment time and improving the therapeutic ratio. Materials and Methods Forty-one patients presenting to the Department of Radiation Oncology, between January 2016 and June 2017, with newly biopsy-proven carcinoma cervix Stage IB to IVA were enrolled in the study, and all the investigations were performed. The radiation dose was delivered using volumetric modulated arc therapy plan according to the dose of 5,000 cGy in 25 fractions to the whole pelvis and 5,500 cGy in 25 fractions to the involved nodes at 220 cGy per fraction using SIB along with weekly cisplatin at 40 mg/m2. After completion of external beam radiation, all the patients received three fractions of brachytherapy to a total dose of 21 Gy. Acute toxicities were assessed using Radiation Therapy Oncology Group criteria. At 3 months after completion of treatment, all the patients were followed up with diffusion-weighted magnetic resonance imaging of abdomen and pelvis to assess the response after 3 months. Results Of 41 carcinoma cervix patients with significantly positive LNs treated with SIB VMAT, 9.8% of the patients (4 patients) had residual nodal disease and 87.8% of the patients (36 patients) had a complete response, and 19.5% (8 patients) had residual disease of primary and 78% (32 patients) had a complete response at 3 months after completion of treatment with only grade I and grade II toxicities. Conclusion Treatment with SIB VMAT in carcinoma cervix patients with significant pelvic LNs shows a very good response with acceptable acute toxicities. But longer follow-up period is required to see if this response translates into better disease-free survival and overall survival.

Comparison of Dosimetric Parameters in Dysphagia Aspiration-Related Structures and Clinical Correlation in Head and Neck Cancer Patients Treated With Radiotherapy.

IntroductionChemoradiotherapy plays a major role in the treatment of head and neck cancer (HNC). Persistent dysphagia following primary chemoradiotherapy for head and neck cancers can have a devastating effect on a patient’s quality of life. Many studies have shown that the dosimetric sparing of critical structures which were included in swallowing such as the pharyngeal constrictor muscle and larynx can provide improved functional outcomes and better quality of life. However, there are no current randomized studies confirming the benefits of such swallowing-sparing strategies. The aim is to evaluate late dysphagia after chemoradiotherapy for head and neck cancer and to examine its correlation with clinical and dosimetric parameters.Materials and methodsThe period of this prospective study was from November 2018 to March 2020. Patients were divided randomly in 1:1 ratio into two groups, group 1 and group 2, each with 25 patients. Group 1 was planned by three-dimensional conformal radiotherapy (3D-CRT) technique and group 2 was planned by intensity-modulated radiotherapy technique (IMRT) technique. Treatment was delivered after approval of radiotherapy plan. To evaluate the dose to dysphagia aspiration-related structures (DARS), these structures were contoured and dose-volume histograms were generated. Various dosimetric parameters of DARS were evaluated. Swallowing status was clinically evaluated based on the Radiation Therapy Oncology Group and the Common Terminology Criteria for Adverse Events, version 5.ResultsA significant advantage was seen with intensity-modulated radiotherapy technique (IMRT) in comparison to three-dimensional conformal radiotherapy (3D-CRT) in terms of mean dose delivered to the pharyngeal constrictor muscles (66.03 Gy vs 68.77 Gy, p=0.003). The mean dose delivered to the combined dysphagia/aspiration-related structures (DARS) was statistically significantly lower in IMRT compared to 3D-CRT (66.15 Gy vs. 70.09 Gy, p<0.001). Other dose-volumes were also reduced in IMRT group (V30: {98.64% vs. 99.88%, p=0.05}; V50: {90.49% vs. 99.02%, p=0.0002}; V60: {83.92% vs. 95.04, p=0.0002}; D50: {70 Gy vs. 71.16 Gy, p=0.001); and D80: {61.18 Gy vs. 67.39 Gy, p=0.01}. Futhermore, the clinical worsening of dysphagia was less common in IMRT group (48% vs. 80%, p=0.039).ConclusionIMRT can reduce the high-dose volumes received by the DARS receiving high doses by sparing these structures through optimization. This may provide a significant additional benefit that could improve dysphagia and hence the quality of life of patients with head and neck cancer.

Association between the cardiac contact distance and the maximum dose at the left anterior descending coronary artery in post mastectomized patients.

The clinical information on the relationship between the cardiac contact distance (CCD), the maximum dose (Dmax) delivered to the left anterior descending (LAD) coronary artery and the mean heart dose has mostly focused on patients with breast-conserving surgery (BCS), being scarce in postmastectomy patients. The aim of this study is to determine the association between the CCD and the Dmax delivered to the LAD. The secondary objective was to evaluate the dosimetric results of comparing three-dimensional conformal radiotherapy (3D-CRT) to intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques for post mastectomized breast cancer patients with irradiation to the left chest wall. 53 cases of women who received adjuvant standard fractionated postmastectomy radiotherapy (PMRT) were used. Three types of plans were created for each patient: 3D-CRT, seven equidistant IMRT fields, and four partial VMAT arcs. Correlations were evaluated using Pearson's correlation coefficient. Plans made with IMRT and VMAT showed improved homogeneity and conformity. Associations between CCD and Dmax to LAD were positive for all three plan types. Compared to 3D-CRT, the modulated intensity plans obtained better dose homogeneity and conformity to the target volume. The LAD and heart doses were significantly lower for IMRT and VMAT plans. The CCD can be used as a predictor of the maximum and mean doses of the LAD. Modulated intensity techniques allow for better dose distribution and dose reduction to the heart and LAD.

Case report on adenoid cystic carcinoma of palate with review of literature

Adenoid cystic carcinoma (ACC) is a malignant tumor of minor salivary glands of the oral cavity, particularly the palate which accounts for about 5–10%. These tumors are slow growing with a high incidence of local recurrence, perineural invasion, and distant metastasis. Here, we report the case of a 69-year-old female who presented with swelling over the hard palate. Computerized tomography shows enhancing lesion along the undersurface of the left side of the hard palate, abutting the maxillary alveolus in the region of the second premolar and first two molars. There was no erosion of the inner cortex of the maxillary alveolus and no extension into the nasal cavity. Following the biopsy, she underwent a left hard palatectomy with upper alveolar resection. The final histopathological report confirmed ACC with no perineural invasion. Following she received adjuvant radiotherapy using an intensity-modulated radiotherapy technique. Now at 6 months of follow-up, there was no evidence of recurrence. Thus, our patient requires long-term follow-up to assess the benefit and survival outcome.

Treatment plan comparison of volumetric-modulated arc therapy to intensity-modulated radiotherapy in lung stereotactic body radiotherapy using either 6- or 10-MV photon energies.

PurposeThe aim of this study was to dosimetrically compare volumetric‐modulated arc therapy (VMAT) with intensity‐modulated radiotherapy (IMRT) techniques using either 6‐ or 10‐MV photon beam energies in lung stereotactic body radiation therapy (SBRT) plans.MethodsThirty patients with primary or metastatic lung tumors eligible for SBRT were randomly selected. VMAT and IMRT treatment plans using either 6‐ or 10‐MV photon energies were generated through automatic SBRT planning software in the RayStation treatment planning system.ResultsFor planning target volume, there was no difference in D 95% for all plans, whereas D 2% and D 50% were significantly increased by 5.22%–5.98% and 2.47%–2.59%, respectively, using VMAT6/10‐MV plans compared to IMRT6/10‐MV plans. When comparing the D max of organs at risk (OARs), VMAT6/10‐MV was 18.32%–47.95% lower than IMRT6/10‐MV for almost all OARs. VMAT6/10‐MV obviously decreased D mean, V 5Gy, V 10Gy, and V 20Gy of whole lung by 9.68%–20.92% than IMRT6/10‐MV. Similar results were found when comparing VMAT6‐MV with IMRT10‐MV or VMAT10‐MV with IMRT6‐MV. The differences in the D 2%, heterogeneity index, and conformity index between 6‐ and 10‐MV plans are not statistically significant. Plans using 6‐MV performed 4.68%–8.91% lower levels of D max of spinal cord, esophagus, great vessels, and trachea and proximal bronchial tree than those using 10‐MV plans. Similarly, D mean, V 5Gy, V 10Gy, and V 20Gy of whole lung were also reduced by 2.79%–5.25% using 6‐MV. For dose fall‐off analysis, the D 2cm and R 50% of VMAT6/10‐MV were lower than those of IMRT6/10‐MV. Dose fall‐off curve based on 10 rings was steeper for VMAT plans than IMRT plans regardless of the energy used.ConclusionsFor lung SBRT plans, VMAT‐based plans significantly reduced OARs dose and steepened dose fall‐off curves compared to IMRT‐based plans. A 6‐MV energy level was a better choice than 10‐MV for lung SBRT. In addition, the dose differences between different techniques were more obvious than those between different energy levels.

Comparison of Dosimetric Parameters and Clinical Outcomes in Inversely Planned Intensity-Modulated Radiotherapy (IMRT) and Field-in-Field Forward Planned IMRT for the Treatment of Breast Cancer.

IntroductionRadiotherapy has been an important component of the multimodality approach to breast cancer treatment. Newer techniques like three-dimensional radiotherapy had led to better dose distribution over the target volume, with tissue inhomogeneity corrections. To improve the uniformity in dose distribution, a newer technique of intensity modulation was developed, namely, intensity-modulated radiotherapy (IMRT). The present study was designed to compare inverse planned IMRT (IP IMRT) and field-in-field forward planned IMRT (FP IMRT) in patients with breast cancer receiving post-modified radical mastectomy (MRM) adjuvant radiotherapy in terms of dosimetric parameters and clinical outcomes.Materials and methodsFifty patients with breast cancer who have undergone MRM and need adjuvant radiotherapy were randomly assigned in a 1:1 ratio into two groups (25 each) of IP IMRT and FP IMRT techniques. The prescribed dose was 50 Gy in 25 fractions over five weeks. In IP IMRT, five to seven tangential beams were used for the chest wall, nodal volumes were placed at suitable angles with beam optimization, and calculation was carried out by the analytical anisotropic algorithm. For FP IMRT, two opposing tangential fields were created in such a way to achieve uniform dose distribution to the planning target volume (PTV), minimizing hot spot regions, and limiting dose to the ipsilateral lung and contralateral breast. Multiple subfields were manually designed to boost the area not included in the dose cloud. The dosimetric parameters were compared for PTV, lungs, heart, left anterior descending coronary artery (LAD), opposite breast, and esophagus.ResultsThe dosimetric parameters in terms of PTV are better for IP IMRT plans compared to FP IMRT plans (V95%: 92.3% vs 75.2%, p = 0.0001; D90%: 47.4 Gy vs 42.9 Gy, p = 0.0001; D95%: 44.9 Gy vs 37.1, p = 0.0004). The ipsilateral lung (V10Gy: 71.9% vs 41%, p = 0.00001; V20Gy: 42.14% vs 36.35%, p = 0.03; V40Gy: 17.31% vs 26.95%, p = 0.00004; Dmean: 20.91 Gy vs 17.88 Gy, p = 0.01) and contralateral lung (V5Gy: 31.8% vs 0.1%, p < 0.00001; V10Gy: 6.2% vs 0.08%, p = 0.0001) received statistically significant lesser doses in terms of low dose parameters in FP IMRT. In the heart, the dosimetric parameter V5 was significantly lower for FP IMRT (61.7% vs 9.7%, p = 0.00001) along with Dmean (10.92 Gy vs 4.01 Gy, p = 0.001). Similarly, LAD parameters showed comparable high dose volumes (V40Gy: 21.02% vs 16.26%; p = 0.29) in both groups and a trend toward reduction in mean dose (17.1% vs 9.2%; p = 0.05) in FP IMRT group, although low dose volumes were higher in IP IMRT group. In contralateral breast, doses in smaller volumes were better for FP IMRT plans (V0.5Gy: 59.7% vs 43.8%, p = 0.01; V0.6Gy: 54.07% vs 37.6%, p = 0.007; V1Gy: 40.9% vs 22.1%, p = 0.001; V2Gy: 28.7% vs 9.4%, p = 0.00003; V5Gy: 12.07% vs 4.2%, p = 0.0001). In esophagus, statistically significant lower doses were seen only in terms of Dmean (10.29 Gy vs 5.1 Gy; p = 0.03) with FP IMRT. No significant difference in terms of skin reactions and dysphagia was seen in both the groups.ConclusionBoth IP IMRT and FP IMRT techniques have advantages and disadvantages, and the superiority of one technique over another cannot be established in this study. The decision for choosing one technique over another can also be based on various patient-related factors weighing the risk of loco-regional recurrences to that of manifesting radiation-induced sequelae.

Investigating the number of radiation fields in intensity-modulated radiotherapy plans of optic nerve sheath meningioma patients using dose gradient index

Purpose: In optic nerve radiotherapy, vital organs are very close to the target volume, they are highly sensitive to radiation and have low dose tolerance. In this regard, evaluating dose fall-off steepness around the target volume is required to assess various intensity-modulated radiation therapy (IMRT) plans in the treatment of the optic nerve sheath meningioma (ONSM) patients. Materials and Methods: Thirteen ONSM patients were analyzed with three IMRT techniques, including three (IMRT-3F), five (IMRT-5F), and seven fields (IMRT-7F). These plans were studied using Dmean, Dmax, D2%, D98%, V100%, uniformity index (UI), homogeneity index (HI), conformity index (CI), and specifically the dose gradient indices (DGIs). Results: The values of Dmax and Dmean for IMRT-3F, IMRT-5F and IMRT-7F were (5637.42 ± 57.08, 5322.84 ± 83.86), (5670.51 ± 67.87, 5383.00 ± 58.45), and (5692.99 ± 31.65, 5405.72 ± 51.73), respectively, which were increased with increment in the number of IMRT fields from 3 to 7. The UI and HI indices were significantly different between IMRT-3F and IMRT-7F (p = 0.010 and p = 0.005, respectively), and CI was close to the ideal value (0.99 ± 0.01) in IMRT-7F. The significant findings of the dose gradient indices represented smaller values in IMRT-7F, which led to a faster dose fall-off, particularly at the 70%-85% isodose levels around the target. Conclusion: Increasing the number of radiation fields in IMRT treatment plans of ONSM patients had a considerable difference in both the dosimetric parameters of the target volume and at-risk organs, as well as the dose gradient indices. Overall, IMRT-7F could be considered as a preferred technique in the treatment of this meningioma.

Skin Surface Dose for Whole Breast Radiotherapy Using Personalized Breast Holder: Comparison with Various Radiotherapy Techniques and Clinical Experiences.

Simple SummaryBreast immobilization with personalized breast holder (PERSBRA) is a promising approach to reduce the toxicity in the lungs and heart during whole breast radiotherapy. In this study, we designed PERSBRA with three different mesh sizes (large, fine and solid) and applied them on a Rando phantom. Hybrid, intensity modulated radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT) techniques were used to deliver a prescribed dose. The dose measurement with EBT3 film and TLD were taken on Rando phantom with no PERSBRA, large mesh, fine mesh, and solid PERSBRA for tumor doses and surface doses. This innovative PERSBRA provides another radiotherapy option for patients with left breast cancer.Purpose: Breast immobilization with personalized breast holder (PERSBRA) is a promising approach for normal organ protection during whole breast radiotherapy. The aim of this study is to evaluate the skin surface dose for breast radiotherapy with PERSBRA using different radiotherapy techniques. Materials and methods: We designed PERSBRA with three different mesh sizes (large, fine and solid) and applied them on an anthropomorphic(Rando) phantom. Treatment planning was generated using hybrid, intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) techniques to deliver a prescribed dose of 5000 cGy in 25 fractions accordingly. Dose measurement with EBT3 film and TLD were taken on Rando phantom without PERSBRA, large mesh, fine mesh and solid PERSBRA for (a) tumor doses, (b) surface doses for medial field and lateral field irradiation undergoing hybrid, IMRT, VMAT techniques. Results: The tumor dose deviation was less than five percent between the measured doses of the EBT3 film and the TLD among the different techniques. The application of a PERSBRA was associated with a higher dose of the skin surface. A large mesh size of PERSBRA was associated with a lower surface dose. The findings were consistent among hybrid, IMRT, or VMAT techniques. Conclusions: Breast immobilization with PERSBRA can reduce heart toxicity but leads to a build-up of skin surface doses, which can be improved with a larger mesh design for common radiotherapy techniques.

Dose-Escalated Intensity-Modulated Radiotherapy for the Management of Locally Advanced Cervical Cancer.

ObjectiveIn this study, we aimed to assess the response and toxicity related to dose escalation in external beam radiation therapy (EBRT) using intensity-modulated radiation therapy (IMRT) with weekly concurrent cisplatin followed by de-escalated brachytherapy (BT) in locally advanced carcinoma cervix of International Federation of Gynecology and Obstetrics (FIGO) 2018 stage IIB-IIIC1.Materials and methodsFifty-two patients diagnosed with cervical cancer FIGO 2018 stage IIB-IIIC1 were treated with curative intent from November 2019 to October 2021. The dose of 50 Gy was prescribed for the primary tumor volume and elective pelvic nodal volume followed by a primary boost to a dose of 20 Gy. Gross lymph node (LN) of size >1 cm after EBRT completion received a sequential nodal boost of 10 Gy. All patients received concurrent cisplatin to a dose of 40 mg/m2 for a total of five to six weekly cycles. All patients received two fractions of BT to a dose of 6 Gy after EBRT completion. Radiation-induced acute toxicities were graded according to the Radiation Therapy Oncology Group (RTOG) criteria and hematologic toxicity was graded according to the Common Terminology Criteria for Adverse Events (CTCAE v4.0).ResultsA median follow-up of six months was available for the 40 eligible patients. All patients tolerated treatment with an acceptable toxicity profile. Grade III dermatitis, grade III gastrointestinal (GI) toxicity, and grade III genitourinary (GU) toxicity were seen in three (7.5%), six (17.5%), and three patients (7.5%) respectively. Grade I anemia was evident in all patients. At six months after EBRT completion, 37 patients (92.5%) had a complete response and only three patients (7.5%) had residual disease.ConclusionBased on our findings, patients with cervical cancer treated with dose-escalated IMRT have a satisfactory outcome with reasonably low levels of treatment-related acute GI and GU toxicities. The findings of the present study endorse the notion that the application of a high dose of external radiation to the pelvis by IMRT technique with image-guided delivery could be an acceptable alternative to the standard-dose management schedule.

Dosimetric and radiobiological comparison in head-and-neck radiotherapy using JO-IMRT and 3D-CRT

IntroductionDosimetric and radiobiological evaluations for the Jaws-only Intensity-modulated radiotherapy (JO-IMRT) technique for head and neck jaws-only intensity-modulated radiation therapy (JO-IMRT) and 3D conformal radiation therapy (3D-CRT). To compare the head-and-neck therapeutic approaches utilizing JO-IMRT and 3D-CRT techniques, different radiation dose indices were calculated, including: conformity index (CI), homogeneity index (HI), and radiobiological variables like Niemierko's equivalent uniform dose based tumor control probability (TCP) of planning target volume (PTV), normal tissue complication probability (NTCP) of organs at risk (OAR) (brainstem, spinal cord, and parotid grand). Materials and methodsTwenty-five nasopharynx patients were studied using the Prowess Panther Treatment Planning System (Prowess Inc). The results were compared with the dose distribution obtained using 3D-CRT. ResultsRegarding tumor coverage and CI, JO-IMRT showed better results than 3D-CRT. The average doses received by the PTVs were quite similar: 72.1 ± 0.8 Gy by 3D-CRT and 72.5 ± 0.6 Gy by JO-IMRT plans (p > 0.05). The mean doses received by the parotid gland were 56.7 ± 0.7 Gy by 3D-CRT and 26.8 ± 0.3 Gy by JO-IMRT (p > 0.05). The HI and CI were 0.13 ± 0.01 and 0.14 ± 0.05 and (p > 0.05) by 3D-CRT and 0.83 ± 0.05 and 0.73 ± 0.10 by JO-IMRT (p < 0.05). The average TCP of PTV was 0.82 ± 0.08 by 3D-CRT and 0.92 ± 0.02 by JO-IMRT. Moreover, the NTCP of the parotid glands, brain stem, and spinal cord were lower using the JO-IMRT than 3D-CRT plans. In comparison to the 3D-CRT approach, the JO-IMRT technique was able to boost dose coverage to the PTV, improve the target's CI and HI, and spare the parotid glands. This suggests the power of the JO-IMRT over 3D-CRT in head-and-neck radiotherapy.

Impact on xerostomia for patients with nasopharyngeal carcinoma treated with superficial parotid lobe-sparing intensity-modulated radiation therapy (SPLS-IMRT): A prospective phase II randomized controlled study.

6059 Background: In the intensity-modulated radiation therapy (IMRT) era, xerostomia remains one of the most common radiation-induced toxicities in nasopharyngeal carcinoma (NPC) patients. We first proposed the superficial parotid lobe–sparing IMRT (SPLS-IMRT) technique in NPC, which has been proved to significantly reduce the mean doses of bilateral entire parotid glands and superficial parotid lobes. To further validate its clinical benefits, we conducted a prospective phase II randomized controlled study to compare the incidence of xerostomia in NPC patients treated with SPLS-IMRT and conventional IMRT (C-IMRT). Methods: Patients with histologically confirmed NPC who met the eligibility criteria were randomly assigned in a 1:1 ratio to receive either SPLS-IMRT or C-IMRT. The V36 (the percentage volume receiving a dose of 36 Gy) of the entire parotid gland was constrained to be less than 40% in both groups. Additionally, V26 (the percentage volume receiving a dose of 26 Gy) of the superficial parotid lobe was constrained to be less than 30% in the SPLS-IMRT group. The primary endpoint was the incidence of xerostomia at 12 months post-IMRT. The secondary endpoints included the xerostomia questionnaire (XQ) score, unstimulated salivary flow rate (USFR), stimulated salivary flow rate (SSFR), and survival outcomes. Results: From January 2018 to September 2018, 90 patients were enrolled (45 per group). Eighty-two patients were included for xerostomia analysis (42 in the SPLS-IMRT group and 40 in the C-IMRT group). At 12 months post-IMRT, the incidence of xerostomia in the SPLS-IMRT group was significantly lower than that in the C-IMRT group (83.4% vs. 95.0%; P = 0.007), especially the grade 3 xerostomia (0% vs. 12.5%; P &lt; 0.001). However, the median change in XQ score (XQchange) was similar between the two groups (11.9 points vs. 14.1 points; P = 0.194). Moreover, there was a significantly higher median fractional USFR (0.67 vs. 0.35; P = 0.024) and SSFR (0.66 vs. 0.32; P = 0.021) in the SPLS-IMRT group than the C-IMRT group. All 90 patients were included for survival analysis. With a median follow-up time of 37.8 months (IQR, 33.9–38.5 months), the 3-year locoregional relapse-free survival, distant metastasis-free survival, and overall survival in the SPLS-IMRT and C-IMRT groups were 92.5% vs. 90.9% (hazard ratio [HR], 1.84; P = 0.477), 83.8% vs. 81.7% (HR, 1.13; P = 0.816), and 88.9% vs. 88.2% (HR, 0.96; P = 0.949), respectively. Conclusions: SPLS-IMRT significantly reduced the incidence of xerostomia at 12 months post-IMRT in NPC by recovering parotid gland function earlier than C-IMRT, without compromising survivals. Phase III clinical trials are needed to confirm this result. Clinical trial information: NCT05020067.

Comparison of plan dosimetry on multi-targeted lung radiotherapy: A phantom-based computational study using IMRT and VMAT

This work analyzed the dosimetric difference between the intensity modulated radiotherapy (IMRT), partial/single/double-arc volumetric modulated arc therapy (PA/SA/DA-VMAT) techniques in treatment planning for treating more than one target of lung cancer at different isocenters. IMRT and VMAT plans at different isocenters were created systematically using a Harold heterogeneous lung phantom. The conformity index (CI), homogeneity index (HI), gradient index (GI), dose-volume histogram and mean and maximum dose of the PTV were calculated and analyzed. Furthermore, the dose-volume histogram and mean and maximum doses of the OARs such as right lung, contralateral lung and non GTV were determined from the plans. The IMRT plans showed the superior target dose coverage, higher mean and maximum values than other VMAT techniques. PA-VMAT technique shows more lung sparing and DA-VMAT increases the V5/10/20 values of contralateral lung than other VMAT and IMRT techniques. The IMRT technique achieves highly conformal dose distribution to the target than other VMAT techniques. Comparing to the IMRT plans, the higher V5/10/20 and mean lung dose were observed in the contralateral lung in the DA-VMAT.

Outcomes of carotid sparing intensity-modulated radiotherapy for early stage glottic cancer in 201 patients: Multicenter study of Turkish Radiation Oncology Society/TROD-01-007.

To assess and report clinical outcomes after carotid sparing intensity-modulated radiotherapy for early stage laryngeal cancer. We retrospectively analyzed 201 patients with early stage glottic laryngeal cancer treated with carotid sparing intensity-modulated radiotherapy (IMRT)/volumetric modulated arc therapy (VMAT) techniques in six TROD centers. After a median follow-up of 31 months the actuarial 1- and 3-year local and locoregional control rates were 99.4% and 94.7%, 98.4% and 93%, respectively. T classification, anterior commissure involvement, IMRT technique, and type of fractionation were not found to be prognostic for local control. Overall, eight patients had lost their organ function due to recurrence or toxicity. Grade 3 and 4 acute laryngeal edema was seen in eight (4%) and one (0.5%) of patients, respectively. Grade 3 and 4 late laryngeal edema developed in two (1%) and one patient (0.5%), respectively. Oncologic outcomes of patients treated with carotid sparing IMRT were excellent; comparable with historical series, with acceptable side effects. Longer follow-up is needed to estimate long term effect on stroke.

Impact of 3D conformal and Intensity Modulated Radiotherapy on secondary cancer risk for patients with early prostate cancer

Secondary cancer resulting from radiation exposure to normal tissues is always a concern. Thus, present study aimed to estimate this risk for patient receiving radiotherapy using advanced techniques like Intensity-modulated radiation therapy (IMRT) and Three-dimensional conformal radiotherapy (3DCRT). Ten prostate cancer cases were chosen, and CT images were acquired for each patient. 3DCRT and IMRT plans were generated and were compared with respect to several dosimetric parameters for Planning Target Volume (PTV) and for Organs at Risk (OARs). The second cancer risks were estimated by Excess absolute risk (EAR) for OARs. For prostate, the PTV dose coverage parameters were significantly improved in IMRT compared to 3DCRT. The rectum and bladder mean dose DMean, V50Gy, and V40Gy were significantly decreased with IMRT in comparison to 3DCRT. The maximum dose (DMax), DMean, V30Gy, and V20Gy for head of femurs significantly decreased with IMRT plans. However, the colon DMean significantly increased with IMRT compared with 3DCRT plans. Compared with the 3DCRT the IMRT plans decreased the organ equivalent dose (OED) in rectum based on the linear, plateau and linear-exponential models. The OED for the bladder also decreased with linear model in IMRT plan. While, the OED for the colon significantly increased in IMRT. The IMRT plans were decreased second cancer risk for the rectum by 10%, 26.6% and 19.5% for linear, plateau and linear-exponential dose-response models respectively. The bladder second cancer risk was decreased by 14% with linear dose-response model in comparison to 3DCRT plans. However, the second cancer risk for colon was significantly increased in average by 91.2% with IMRT plans. IMRT technique demonstrated a clear advantage in dose coverage, conformity, and homogeneity over 3DCRT and was superior in terms of OAR-sparing. The Second cancer risk for in field organs (rectum and bladder) was decreased with IMRT compared to 3DCRT plan.

Attention-aware 3D U-Net convolutional neural network for knowledge-based planning 3D dose distribution prediction of head-and-neck cancer.

PurposeDeep learning–based knowledge‐based planning (KBP) methods have been introduced for radiotherapy dose distribution prediction to reduce the planning time and maintain consistent high‐quality plans. This paper presents a novel KBP model using an attention‐gating mechanism and a three‐dimensional (3D) U‐Net for intensity‐modulated radiation therapy (IMRT) 3D dose distribution prediction in head‐and‐neck cancer.MethodsA total of 340 head‐and‐neck cancer plans, representing the OpenKBP—2020 AAPM Grand Challenge data set, were used in this study. All patients were treated with the IMRT technique and a dose prescription of 70 Gy. The data set was randomly divided into 64%/16%/20% as training/validation/testing cohorts. An attention‐gated 3D U‐Net architecture model was developed to predict full 3D dose distribution. The developed model was trained using the mean‐squared error loss function, Adam optimization algorithm, a learning rate of 0.001, 120 epochs, and batch size of 4. In addition, a baseline U‐Net model was also similarly trained for comparison. The model performance was evaluated on the testing data set by comparing the generated dose distributions against the ground‐truth dose distributions using dose statistics and clinical dosimetric indices. Its performance was also compared to the baseline model and the reported results of other deep learning‐based dose prediction models.ResultsThe proposed attention‐gated 3D U‐Net model showed high capability in accurately predicting 3D dose distributions that closely replicated the ground‐truth dose distributions of 68 plans in the test set. The average value of the mean absolute dose error was 2.972 ± 1.220 Gy (vs. 2.920 ± 1.476 Gy for a baseline U‐Net) in the brainstem, 4.243 ± 1.791 Gy (vs. 4.530 ± 2.295 Gy for a baseline U‐Net) in the left parotid, 4.622 ± 1.975 Gy (vs. 4.223 ± 1.816 Gy for a baseline U‐Net) in the right parotid, 3.346 ± 1.198 Gy (vs. 2.958 ± 0.888 Gy for a baseline U‐Net) in the spinal cord, 6.582 ± 3.748 Gy (vs. 5.114 ± 2.098 Gy for a baseline U‐Net) in the esophagus, 4.756 ± 1.560 Gy (vs. 4.992 ± 2.030 Gy for a baseline U‐Net) in the mandible, 4.501 ± 1.784 Gy (vs. 4.925 ± 2.347 Gy for a baseline U‐Net) in the larynx, 2.494 ± 0.953 Gy (vs. 2.648 ± 1.247 Gy for a baseline U‐Net) in the PTV_70, and 2.432 ± 2.272 Gy (vs. 2.811 ± 2.896 Gy for a baseline U‐Net) in the body contour. The average difference in predicting the D 99 value for the targets (PTV_70, PTV_63, and PTV_56) was 2.50 ± 1.77 Gy. For the organs at risk, the average difference in predicting the Dmax (brainstem, spinal cord, and mandible) and Dmean (left parotid, right parotid, esophagus, and larynx) values was 1.43 ± 1.01 and 2.44 ± 1.73 Gy, respectively. The average value of the homogeneity index was 7.99 ± 1.45 for the predicted plans versus 5.74 ± 2.95 for the ground‐truth plans, whereas the average value of the conformity index was 0.63 ± 0.17 for the predicted plans versus 0.89 ± 0.19 for the ground‐truth plans. The proposed model needs less than 5 s to predict a full 3D dose distribution of 64 × 64 × 64 voxels for a new patient that is sufficient for real‐time applications.ConclusionsThe attention‐gated 3D U‐Net model demonstrated a capability in predicting accurate 3D dose distributions for head‐and‐neck IMRT plans with consistent quality. The prediction performance of the proposed model was overall superior to a baseline standard U‐Net model, and it was also competitive to the performance of the best state‐of‐the‐art dose prediction method reported in the literature. The proposed model could be used to obtain dose distributions for decision‐making before planning, quality assurance of planning, and guiding‐automated planning for improved plan consistency, quality, and planning efficiency.

Does CyberKnife improve dose distribution versus IMRT and VMAT on a linear accelerator in low-risk prostate cancer?

BackgroundHypofractionated stereotactic body radiation therapy (SBRT) for prostate cancer (PCa) can be delivered with the robot-assisted CyberKnife (CK) system or on a linear accelerator using dynamic intensity-modulated radiotherapy (IMRT) or volumetric arc radiotherapy (VMAT). This retrospective study was performed to determine whether CK offers better dose distribution than IMRT and/or VMAT.Materials and methodsTreatment plans for three techniques were prepared using the same treatment parameters (36.35 Gy, 7.25 Gy/fr). We evaluated target coverage, conformity index (CI), homogeneity index (HI), gamma index (GI), and organs at risk (OAR) constraints.ResultsThe mean planning target volume (PTV) dose for CK (39.58 Gy) was significantly greater than VMAT or IMRT (both 36.25 Gy). However, CK resulted in a wider dose range (31.48 to 45.89 Gy) vs. VMAT and IMRT (34.6–38.76 Gy). The mean dose to the rectum (V36Gy, mm3) was significantly lower (p < 0.001) in the CK plans (219.78 vs. 519.59 and 422.62, respectively). The mean bladder dose (V37Gy, mm3) was significantly greater for CK (3256 vs. 1090.75 for VMAT and 4.5 for IMRT (p < 0.001). CK yielded significantly better CI (1.07 vs. 1.17 and 1.25 for VMAT and IMRT, respectively; p < 0.01) and HI values (1.27 vs. 1.07 and 1.04; p < 0.01). GI values for the δd = 3mm, δ% = 3% criteria were 99.86 (VMAT), 99.07 (IMRT) and 99.99 (CK). For δd = 2mm, δ% = 2%, the corresponding values were 98.3, 93.35, and 97.12, respectively.ConclusionsFor most variables, CK was superior to both VMAT and IMRT. However, dynamic IMRT techniques, especially VMAT, do not differ significantly from CK plans and are therefore acceptable alternatives to CyberKnife.

Abstract P1-21-02: Scalp sparing whole-brain radiotherapy using IMRT technique. Do we need it?

Abstract Introduction: The prognosis of metastatic breast cancer patients is improving due to advances in systemic therapy, which led to better control of the disease. Brain metastasis that requires whole-brain radiotherapy (WBRT) is mandatory for some patients.Acute alopecia is a common side effect, and total hair loss occurs in 100% of patients receiving parallel opposed direct laterals fields.Because of the recognized reduction in quality of life associated with clinically apparent and clinically undetectable hair loss, efforts are made to minimize hair loss resulting from WBRT.It is theorized that intensity-modulated radiotherapy (IMRT) may reduce hair loss. It will be less patchy because IMRT enables dose modulation, minimizing the radiation dose received by the hair follicles in the scalp.This dosimetric study assessed the dose received to the whole scalp and its subvolumes by three radiotherapy techniques. Methods: A total of 30 treatment plans for ten patients receiving WBRT were evaluated retrospectively. All patients were simulated in a supine position with a thermoplastic mask. The scalp was contoured as 5 mm between the skin and the outer table of the skull. Then we subdivided the scalp volume into superior, anterior, lateral, and posterior subvolumes. The dose prescribed was 30 Gy in 10 fractions. We compared three different radiotherapy techniques using the standard WBRT procedure that involves applying two lateral opposing fields (OF-WBRT) with a margin surrounding the brain, which includes the hair follicles situated about 5 mm. below the scalp, the field in field (FiF), and IMRT techniques without introducing the scalp in the optimization process using 6 MV photon energy. Results: All techniques showed comparable PTV coverage. The homogeneity index with opposed lateral was 0.057±.09, 0.057±.0111 for FiF, and 058±.0114 for IMRT with no statistically significant difference (p = 0.407).IMRT resulted in a marked decrease in all scalp parameters with a statistically significant difference, with a little difference in the dose delivered to lateral subvolumes. (table 1) Conclusion: Scalp sparing IMRT for WBRT reduces the scalp dose compared to conventional WBRT, especially in the superior, anterior and posterior axis. Further randomized prospective trials are needed to confirm this benefit. 2 Table. PTV coverage and dose to the scalp and its subvolumes.characteristicsOPPOSED LATERALFIFIMRTP-ValueMean ± SDMean ± SDMean ± SDAll groupsOpposes lateral/FIFOpposes lateral/IMRTIMRT/FIFPTV D 98%96.9±0.796.9±0.797.1±0.71.000Scalp mean dose (cGy)2165.7±270.52120.5±242.81385.9±306.7&amp;lt;0.0010.076&amp;lt;0.0010.076Scalp V 20 (%)68.4±12.567.1±11.237.6±11.2&amp;lt;0.0010.221&amp;lt;0.0010.042Superior mean dose (cGy)2396.8±138.92326.1±1211419.0± 372.4&amp;lt;0.0010.076&amp;lt;0.0010.076Anterior mean dose (cGy)2180.9±237.82209.7±205.01267.4±462.2&amp;lt;0.0010.221&amp;lt;0.0010.042Lateral mean dose (cGy)2127.7±252.62136.9±249.12071.4±257.10.0020.2210.2210.001Posterior meanDose (cGy)2317.8±205.62273.3±207.81467.2±209.7&amp;lt;0.0010.0760.076&amp;lt;0.001 Citation Format: Mohsen Samy Barsoum, Emad Mohsen Barsoum, Maha Kamaleldin, Niven Mahmoud, Shaimaa Abdelgeleel, May Gamal Ashour. Scalp sparing whole-brain radiotherapy using IMRT technique. Do we need it? [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-21-02.

DOSIMETRIC COMPARISON OF HEART DOSE WITH 3DCRT VS IMRT IN POST-MASTECTOMY LEFT SIDED CHEST WALL IRRADIATION

Purpose: Data regarding the efficacy of various radiotherapy techniques for post mastectomy chest-wall radiotherapy (PMRT) using hypofractionation is scarce and cardiac toxicity remains a concern.This study aims to compare effect of IMRT (Intensity Modulated Radiation Therapy) and 3D-CRT (3-Dimensional Conformal Radiation Therapy) techniques on cardiac dose. Materials and Methods: In this retrospective study,we compared IMRT and 3DCRT plans of 20 patients who received PMRT to a dose of 42.56Gy/16# and the dosimetric parameters in terms of planning target volume (PTV) coverage and dose to organ at risk (OARs) including heart and ipsilateral lung were recorded and analyzed. Result: PTV coverage were comparable with both techniques. IMRT planning provided a better conformity index as compared with 3DCRT (0.95 vs 0.91, p&lt;0.001).The mean dose to the heart significantly reduced with IMRT (4.36Gy vs 8.2Gy,p&lt;0.00001). Conclusion: IMRT offers a significant reduction in mean heart dose than 3DCRT in patients treated with hypofractionated post-mastectomy irradiation.

Comparison of Cervical Cancer Radiation in Bladder Organs with 10 MV LINAC Energy Radiotherapy Using 3DCRT and IMRT Techniques at Sanglah Hospital Denpasar

A study has been conducted on comparative analysis of cervical cancer radiation to the bladder organ with 10 MV energy LINAC (Linear Accelerator) radiotherapy using the 3DCRT (Three Dimension Conformal Radiotherapy) technique and the IMRT (Intensity Modulated Radiation Therapy) technique at Sanglah Hospital, Denpasar. The 3DCRT and IMRT techniques were compared by analyzing the values ??of the HI (Homogeneity Index), CI (Conformity Index) and radiation dose distribution in the OAR (Organ At Risk), namely the bladder. The data used are 30 cervical cancer patient data with 10 MV photon beam radiotherapy planning and a total radiation dose of 5000 cGy. In calculating the HI and CI values, the data used were radiation dose of 98%, 50%, 2% of target volume and 95% volume on PTV and the average dose on Bladder organs. The data was obtained from the DVH (Dose Volume Histogram) statistics contained in the TPS (Treatment Planning System). The results of the HI value of 0.0818 for the 3DCRT technique and 0.0899 for the IMRT technique with statistical test results obtained the Asimp.Sig (2-tailed) value of 0.056&gt; 0.05 which means it is not significant, while for the results of the CI value of 0.9500 for the 3DCRT technique and 0.9499 for the IMRT technique with statistical test results obtained the Asimp.Sig (2-tailed) value of 0.970&gt; 0.05 which means it is not significant, meanwhile the percentage of the average dose in the bladder organ obtained an average result from the 3DCRT and IMRT irradiation techniques, 96% and 88%, respectively, with statistical test results, the Asimp.Sig (2-tailed) value was 0.000 &lt;0.05, which was significant. Cervical cancer radiation using the IMRT technique is better than the 3DCRT technique because the IMRT technique minimizes the absorbed dose in OAR, it can be seen from the percentage of the average dose in the bladder organ with the IMRT technique getting a smaller dose percentage.