3DCRT Plans Research Articles

Impact of log file source and data frequency on accuracy of log file-based patient specific quality assurance

Performing phantom measurements for patient-specific quality assurance (PSQA) adds a significant amount of time to the adaptive radiotherapy procedure. Log file based PSQA can be used to increase the efficiency of this process. This study compared the dosimetric accuracy of high-frequency linear accelerator (Linac) log files and low-frequency log data stored in the oncology information system (OIS). Thirty patients were included, that were recently treated in the head and neck (HN), brain, and prostate region with volumetric modulated arc therapy (VMAT) and an additional ten patients treated using stereotactic body radiation therapy (SBRT) with 3D-conformal radiotherapy (3D-CRT) technique. Log data containing a single fraction were used to calculate the dose distributions. The dosimetric differences between Linac log files and OIS logs were evaluated with a gamma analysis with 2%/2 mm criterion and dose threshold of 30%. The original treatment plan was used as a reference. Moreover, DVH parameters of D98%, D50%, and D2% of the planning-target volume (PTV) and dose to several organs at risk (OARs) were reported. Significant differences in dose distributions between the two log types and the original dose were observed for PTV D98% and D2% (r < 0.001) for HN cases, PTV D98% (r = 0.005) for brain cases, and PTV D50% (r = 0.015) for prostate cases. No significant differences were found between the two log types with respect to D50%. The root mean square (RMS) error of the leaf positions of the OIS log was approximately twice the RMS error of the Linac log file for VMAT plans, but identical for 3D-CRT plans. The relationship between the gamma pass rate and the RMS error showed a moderate correlation for the Linac log files (r = −0.58, p < 0.001) and strong correlation for OIS logs (r = −0.71, p < 0.001). Furthermore, all doses calculated using Linac log files and OIS log data had a GPR >90% for an RMS error < 3.3 mm. Based on these findings, a tolerance limit of RMS error of 3.3 mm for considering OIS log based PSQA was established. Nevertheless, the OIS log data quality should be improved to achieve adequate PSQA.

Analysis of fetal dose using Optically Simulated Luminescence Dosimeter and ion chamber in randophantom for various radiotherapy techniques

To analyse the fetal dose in all three trimesters in patients treated for brain tumors during pregnancy, a modified rando phantom representing three different trimesters was used with provisions for insertion of ion-chamber and Optically Simulated Luminescence Dosimeter (OSLD). The measurement regions were chosen at the level of fundus, umbilicus and pubis. Seven different treatment plans with 6FF and 6FFF beam energies were generated. Treating pregnant patients with brain tumors is safe irrespective of planning modalities except 3DCRT plan where the dose is 10.24 cGy.

Dosimetric comparison between proton beam therapy, intensity modulated radiation therapy, and 3D conformal therapy for soft tissue extremity sarcoma

Purpose/objectives Proton beam therapy (PBT) may provide a dosimetric advantage in sparing soft tissue and bone for selected patients with extremity soft sarcoma (eSTS). We compared PBT with photons plans generated using intensity-modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3D-CRT). Materials/methods Seventeen patients previously treated with pencil beam scanning PBT were included in this study. Of these patients, 14 treated with pre-operative 50 Gy in 25 fractions were analyzed. IMRT and 3D-CRT plans were created to compare against the original PBT plans. Dose-volume histogram (DVH) indices were evaluated amongst PBT, IMRT, and 3D plans. Kruskal–Wallis rank sum tests were used to get the statistical significance. A p value smaller than .05 was considered to be statistically significant. Results For the clinical target volume (CTV), D2%, D95%, D98%, Dmin, Dmax, and V50Gy, were assessed. Dmin, D1%, Dmax, Dmean, V1Gy, V5Gy, and V50Gy were evaluated for the adjacent soft tissue. D1%, Dmax, Dmean, and V35-50% were evaluated for bone. All plans met CTV target coverage. The PBT plans delivered less dose to soft tissue and bone. The mean dose to the soft tissue was 2 Gy, 11 Gy, and 13 Gy for PBT, IMRT, and 3D, respectively (p < .001). The mean dose to adjacent bone was 15 Gy, 26 Gy, and 28 Gy for PBT, IMRT, and 3D, respectively (p = .022). Conclusion PBT plans for selected patients with eSTS demonstrated improved sparing of circumferential soft tissue and adjacent bone compared to IMRT and 3D-CRT. Further evaluation will determine if this improved dosimetry correlates with reduced toxicity and improved quality of life.

Case study: Dosimetric comparison of VMAT, IMRT and 3DCRT techniques for left-sided breast cancer treated in deep inspiration breath-hold

The aim of this case study was to compare 3D conformal radiotherapy (3DCRT) plans for patients treated for left-sided breast cancer (whole breast without positive lymph nodes in deep inspiration breath-hold (DIBH)) to volumetric modulated arc therapy (VMAT) and intensity modulated radiation therapy (IMRT) plans. The original clinical plans used tangential field-in-field 3DCRT technique with a combination of 6 MV and 18 MV photon beams. VMAT and IMRT plans were based on several previously published techniques and used 6 MV beams. Two patients were included in this case study and 4 plans were created and compared for each one. All plans were compared in terms of tumour coverage, gradient measure and conformity index, doses to organs at risk (OARs), the volume of body receiving 5 Gy and also the number of Monitor Units (MUs). While better tumour coverage and conformity was achieved with IMRT and VMAT plans, OARs were better spared with the 3DCRT technique, which also resulted in the lowest dose bath and number of MUs.

166P A mono-institutional experience of field-in-field 3D-CRT planning in breast radiotherapy with FAST and FAST-forward protocols

The benefits of hypofractionated radiotherapy with FAST and FAST-forward protocols could be compromised by soft tissue reactions and cardiac toxicity caused by dose inhomogeneity and inaccurate heart sparing. This study aims to evaluate the dosimetric results of whole-breast hypofractionated radiotherapy with the field-in-field 3D conformal radiotherapy (3D-CRT) technique. A mono-institutional consecutive cohort of 122 early-stage invasive breast cancer patients was treated using field-in-field 3D-CRT. Thirty-nine patients were treated with 28.5 Gy in 5 fractions once a week (FAST protocol) and eighty-three patients with 26 Gy in 5 consecutive fractions (FAST-forward protocol). Different parameters were evaluated to assess target coverage, dose conformity and homogeneity and hot spots in unspecified tissues. To assess breast dimensions, nipple-to-pectoral muscle distance (NPD) and maximum mediolateral thickness (MLT) along tangential fields were measured. Evaluated OARs were ipsilateral lung and heart with their respective dose constraints as required by the clinical protocols. The median NPD and MLT were 4.65 cm [1.70-9.30] and 21.55 cm [11.26-32.30] respectively, with a median CTV of 380.50 cm3 [60.29-1255.13]. The median V95% was 99.45% [95.19-100], and the median 105% isodose volume was 0.74 cm3 [0.00-48.02] of whom 0.07 cm3 [0.00-5.22] in the first skin centimetre. This led to a median CI of 0.53 [0.33-1.00] and a median HI of 0.07 [0.03-0.19]. OARs dose-volume constraints were always respected. The median ipsilateral lung V8Gy was 7.32% [0.31-25.15]; as for the heart (left breast only), the median V1.5Gy was 6.45% [0.00-25.12] and median V7Gy was 0.34% [0.00-4.50]. Each plan achieved a clinically acceptable target coverage and homogeneity, with reduced superficial hot spots. These results suggested that field-in-field 3D-CRT can provide good quality FAST and FAST-forward breast RT plans, with the advantages of an efficient and cost-effective delivery technique. The clinical follow-up will give further critical feedback on treatment outcomes and toxicities.

Dosimetric comparison between carotid-sparing IMRT and 3DCRT in early glottic cancer patients treated with definitive radiation therapy.

The purpose of this study was to evaluate the dosimetric benefits of carotid-sparing IMRT (intensity-modulated radiation therapy) over 3DCRT (three-dimensional conformal radiation therapy) in early glottic cancer patients. Ten patients with histologically proven early-stage squamous cell cancer of glottis (T1N0), treated with definitive radiotherapy, were selected retrospectively for the dosimetric analysis. Patients were originally treated with 3DCRT technique. For comparison purpose, IMRT plans were generated for each patient. Dosimetric comparison was done between two techniques (IMRT and 3DCRT) in terms of PTV (planning target volume) coverage, HI (homogeneity index), CI (conformity index), and doses to right carotid artery, left carotid artery, and spinal cord. V95% for the PTV was higher in IMRT plans (98.26%) as compared to 3DCRT plans (95.12%) (P-value <0.001), whereas V105% for PTV was significantly higher in 3DCRT plans (16.77%) as compared to IMRT plans (0.32%) (P-value 0.11). In terms of both HI and CI, IMRT plans showed better conformity as compared to 3DCRT plans, with statistically significant difference. Both right and left carotid arteries' average mean and maximum doses were significantly lower in IMRT plans as compared to 3DCRT plans (P-value <0.001). IMRT plans resulted in significant carotid-sparing as compared to 3DCRT plans in terms of V35 and V50 (P-value <0.001). Carotid-sparing IMRT resulted in better PTV coverage and lower carotid artery dose as compared to 3DCRT in early glottic cancer patients.

Validation of esophageal cancer treatment methods from 3D-CRT, IMRT, and Rapid Arc plans using custom Python software to compare radiobiological plans to normal tissue integral dosage.

The aim was to develop in-house software that is able to calculate and generate the biological plan evaluation of the esophagus treatment plan using the Niemierko model for normal tissue complication probability and tumor control probability. The Niemierko model can be applied for esophagus cancer treatment plan to estimate the tumor control probability (TCP) and the normal tissue complication probability (NTCP) using different planning techniques. The equivalent uniform dose (EUD) and effective volume parameters were compared with organ at risk. Subsequently, EUD and TCP parameter were compared with tumor volume for all five different planning techniques. Ten cases for esophageal cancer were included in this study. For each patient, five treatment plans were generated. The Anisotropic analytical algorithms (AAA) were used for dose calculation for the three-dimensional conformal radiation therapy (3D-CRT), intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques. The in-house developed radiobiological plan evaluation software using python programming is used for this study which takes a dose volume histogram (DVH) text file as an input file for biological plan evaluation. EUD, NTCP, TCP and effective volume were calculated from the Niemierko model using the in-house developed python based software and compared with treatment monitor units (MU) with all five different treatment plan. The best technique is quantified as benchmarked out of other different qualities of treatment. The four field 3D-CRT treatment plan is found to be the best suited from the perspective of biological plan index evaluation among the other planning techniques.

Dosimetric Comparison of 3-Dimensional Conformal Radiotherapy (3DCRT), Intensity Modulated Radiotherapy (IMRT) and Volumetric-Arc Radiotherapy (VMAT) in Cervical Cancer Treatment

Background: Cervical cancer being the fourth most frequently diagnosed cancer, concurrent chemoradiation forms the mainstay of the treatment from stage IB3 to IVA. As we witnessed advancement in radiotherapy technologies, attempts had been taken to reduce the dose to the OARs without compromising the tumor coverage. In this study we will compare the PTV coverage, conformity index and doses received by the OARs (urinary bladder, rectum, bowel bag, bilateral head of femur) by all the three techniques namely 3DCRT, IMRT and VMAT for carcinoma cervix patients undergoing concurrent Chemoradiotherapy (CRT) at our institution and further implement the results in our clinical practice. Material and Methods: Forty-five of biopsy-proven carcinoma cervix in stage IIA to IIIB were taken up for the study. Following imaging, contouring was carried out using the principal clinical findings and conventional RTOG recommendations. Dose prescription to the cervix was 50 Gy in 25 fraction and planned with all three modalities, 3DCRT, IMRT and VMAT. The patient was treated with the 3DCRT plan and the IMRT and VMAT plans were made for dosimetric purpose only. Results: Quantitative dose evaluation performed of three techniques V40, V45, V50, Dmean for Bladder and Rectum, Dmean and D100 for Femur, V30, V40, D195 CC, Dmean for Bowel. Results show that VMAT plan is preferable than IMRT for sparing Bladder and rectum. Conclusion: IMRT and VMAT both could be advocated for practice was tumor coverage was almost similar in both of them and decision could be made on patient specific logistics.

Planning experience of new graduate radiation therapists in New Zealand.

This research assessed the preparedness of new graduate radiation therapists (NGRTs) for the clinical practice of planning. A senior planner from each department and NGRTs who completed their degree in 2020 were surveyed after approximately 6 months of practice. Both were asked about NGRTs preparedness for practice and for feedback on the Bachelor of Radiation Therapy (BRT) planning curriculum. NGRTs were asked about body sites planned, how many plans they completed and planning techniques they had used. Senior planners were asked about their expectations of NGRTs in planning. New graduate radiation therapists frequently planned using three-dimensional conformal radiation therapy (3DCRT) or virtual simulation (VSim). Commonly planned body sites were those with palliative intent, radical breast and sites more frequently planned using 3DCRT. The departmental sign-off process sometimes prevented them from generating VMAT plans. They suggested more VMAT teaching could be included in the BRT. Senior planners expected NGRTs to be able to plan using 3DCRT and VMAT/IMRT. They suggested more clinical workflow teaching in the BRT planning curriculum. The majority of NGRTs and senior planners felt the BRT prepared the NGRTs for clinical practice. The undergraduate degree is preparing NGRTs for clinical practice in planning. 3DCRT and VSim planning techniques remain a core role of NGRTs and a large proportion of clinical workload. NGRTs utilised their VMAT/IMRT planning skills less often during their initial period of practice, despite being expected to possess these skills. This is a challenge for the undergraduate curriculum and NewZealand departments as the clinical use of VMAT/IMRT continues to increase.

Dosimetric Comparison between Intensity Modulated Radiation Therapy (IMRT) and Three-Dimensional Conformal Radiation Therapy (3DCRT) in Mid Lower esophageal Carcinoma: An Analytical Observational Study

Esophageal cancer (EC) is a common cancer with high mortality because of its rapid progression and poor prognosis. One of the most successful therapies for EC is radiotherapy. Two recently created radiation methods are intensity-modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3D-CRT). In terms of target coverage, dose homogeneity, and lowering toxicity to healthy organs, IMRT is thought to be superior to 3D-CRT. These benefits haven't been proven in the treatment of EC, though. This study was performed to investigate if intensity modulated radiation therapy (IMRT) offers a better planning target volume (PTV) coverage and/or lower dose to organs at risk in comparison to three-dimensional conformal radiation therapy (3DCRT). 30 patients with locally advanced histo-pathologically proven mid and lower oesophageal carcinoma, not reaching gastro-esophageal junction were treated with chemoradiation using IMRT technique. 3DCRT plans were generated for those 30 patients. The IMRT and 3DCRT plans were compared in terms of PTV coverage and doses to organs at risk. Our results revealed that IMRT is better than 3DCRT comparing PTV coverage and doses to organs at risk having statistically significant difference between both techniques (p&lt;0.001). As for the organs at risk (OAR), the V20 for the IMRT plans delivered lesser lung volume irradiation also the mean dose to the heart and the V30 were both higher in the 3DCRT plans.Keywords: esophageal cancers (ECs), Organs at risk (OAR), Intensity modulated radiation therapy (IMRT), Three-dimensional conformal radiation therapy (3DCRT), Planned target volume (PTV).

Secondary cancer risk assessment after high-risk and intermediate-risk prostate cancer radiotherapy in Senegal

Purpose: This study aims at evaluating the excess absolute risk (EAR) of cancer in thirty patients with high and intermediate risks of prostate cancer based on the Amico’s classification, who received a three-dimensional conformal radiotherapy (3DCRT) or a modulated volumetric arc therapy (VMAT) with 6 MV photons energy. Materials and Methods: VMAT plans were performed in simultaneous integrated boost, with 76 Gy to prostate and 56 Gy to pelvic lymph node and seminal vesicle. 3DCRT planning was realized in two stages with prostate, seminal vesicles, and pelvic lymph node receiving 46 Gy, in the first stage, and in the second stage, prostate prescribed at 28 Gy. The EAR was assessed using the Schneider concept based on the equivalent dose for a given organ (OED). Thus, the EAR of the rectum, bladder, pelvic bone and healthy pelvic tissues were calculated and compared on the basis of the Mechanistic, Exponential Linear, Plateau and Sarcoma specific Mechanistic models. Results: The EAR in the rectum were found to be higher in 3DCRT than in VMAT. The EAR values ranged from 3.98-5.37 for the rectum, and from 1.05-3.76 for the bladder depending on the model used. Conclusion: The overall EARs analysis for both radiation modalities indicated that the risk of induction of carcinoma in the rectum was higher with 3DCRT, compared with VMAT. However, it would be necessary for validation of predicted models, to conduct prospective clinal trials with a larger patient cohort

Impact of dose distribution on rotational setup errors in radiotherapy for prostate cancer.

This study aimed to assess the impact of rotational setup errors on the target volume's dose distribution during radiotherapy for prostate cancer. A 6D robotic couch was used to describe the rotational setup error, and the dosage change in the target volume was analyzed using the planning evaluation factors. Treatment plans for three-dimensional conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT), and volumetric modulated arc radiotherapy (VMAT) were established after contouring the target volume and surrounding normal tissues on tomography obtained from the humanoid phantom. A 6D robotic couch was employed in the radiation room to describe the rotational setup errors of ±1° to ±5° in roll, yaw, and pitch, and cone beam computed tomography (CBCT) images were obtained. Furthermore, the dose distribution was extracted from the 3DCRT, IMRT, and VMAT treatment plans, dose mapping was performed on CBCT that depicts the rotational setup error. Target coverage(TC) decreased by 0.39% to 2.17% in roll, 0.43% to 2.59% in yaw, and 0.70% to 4.12% in pitch, respectively. In the comparison using the Radiation Therapy Oncology Group (RTOG) protocol criteria, when the rotational setup error of VMAT pitch was -2° or more, more than +1°, a target coverage of 95% or lower was shown, indicating the greatest effect among rotational setup errors. Furthermore, in 3DCRT, IMRT, and VMAT, the rotational setup error showed the greatest effect in pitch, and the dose change was larger in VMAT than in 3DCRT and IMRT. Therefore, specific rotational error due to pitch during radiotherapy for prostate cancer requires special consideration. Moreover, the more sophisticated and complex algorithms, such as VMAT, applied, the greater the dose change of target coverage due to rotational error; therefore, caution is required.

Evaluation of 3D-CRT and VMAT Radiotherapy Plans for Left Breast Cancer with Regional Lymph Nodes Irradiation

Evaluation of 3D-CRT and VMAT Radiotherapy Plans for Left Breast Cancer with Regional Lymph Nodes Irradiation

Dosimetric comparison of three-dimensional (3D), intensity-modulated radiotherapy (IMRT) and hybrid IMRT for left-sided postmastectomy radiation therapy (PMRT)

Abstract Purpose: This study aimed to determine the suitable breast treatment technique for a small facility’s hospital with limited staff and equipment resources. The benefits and drawbacks of each technique should be considered to guide radiation oncologists choose the appropriate treatment option for postmastectomy radiation therapy (PMRT) patients. Methods and Materials: This study included the computed tomography images of 15 patients who received left-sided PMRT. The patient’s characteristics were classified into two groups: 1. irradiation of only the chest wall (CW) and 2. CW lymph nodes plus supraclavicular lymph nodes (SPCs). All 15 PMRT patients were generated in 4 treatment techniques including 3DCRT, field-in-field (FiF), intensity-modulated radiotherapy (IMRT) and hybrid (3DCRT + IMRT). Each treatment technique’s dosimetric parameters and treatment time were compared. Result: All four treatment plans met the acceptable criteria. The IMRT plans achieved the highest plan quality scores for two groups of PMRT patients but require the longest treatment time, whereas the 3DCRT and FiF plans demonstrated superiority for organ at risk (OAR) sparing and required the shortest treatment time when compared with the IMRT and hybrid plans. Conclusion: The IMRT plan had the highest plan quality but required the most time to treat. Treatment times are critical in facilities with limited resources. As a result, the FiF plan was found to be a suitable technique for both CW-only and CW plus SPC irradiation due to its short treatment time and high plan quality scores for OAR dose sparing.

Dosimetric comparative study of conformal radiation techniques in patients with glioblastoma multiforme

Purpose: The purpose of the current study is to determine whether patients diagnosed with glioblastoma multiforme (GBM) who underwent radiotherapy (RT) using intensity-modulated RT (IMRT) technique were benefitting from this highly conformal treatment in terms of doses received by planning target volume (PTV) and organs at risk (OARs) in comparison to three-dimensional conventional RT (3DCRT). Materials and Methods: Twelve patients treated with IMRT for GBM were selected for dosimetric comparison with 3DCRT. The prescribed dose was 60 Gy in 30 fractions and seven non-coplanner beams were used in IMRT to cover 95% of target volume. The irradiated patients of GBM were retrieved and replanned with 3DCRT techniques. Dosimetric comparison was done by performing two plans for the same patient; prescription dose and normal tissue constraints were identical for both plans. The dose–volume histograms of target volumes and OAR, dose conformity, and dose homogeneity with 3DCRT and IMRT planning were compared. Statistical analysis was performed to determine the differences. Results: The mean conformity index was 0.99 ± 0.001 for IMRT and 0.97 ± 0.002 for 3DCRT, P = 0.001. The mean homogeneity index was 1.03 ± 0.02 for IMRT and 1.06 ± 0.009 for 3DCRT, P = 0.003, which is statistically significant. The IMRT technique enables dose reduction of normal tissues including brainstem (Dmean by 33.78 ± 5.34 and Dmax 51.84 ± 4.43), optic chiasm (Dmean by 36.92 ± 1.99 and Dmax 44.61 ± 3.72), left optic nerve (Dmean by 28.97 ± 6.51 and Dmax 46.08 ± 10.58), right optic nerve (Dmean by 31.93 ± 11.68 and Dmax 44.63 ± 13.54), left eye (Dmean by 18.66 ± 8.92 and Dmax 37.43 ± 13.47), right eye (Dmean by 14.40 ± 4.87 and Dmax 40.37 ± 11.37), left lens (by Dmax 5.45 ± 1.85), and right lens (Dmax 5.07 ± 0.63). Conclusion: The IMRT provides a real dosimetric advantage, especially for normal brain tissue, and in terms of target coverage. It allows treatment of tumors while respecting OARs' dose constraints. The IMRT technique shows significant advantage in PTV coverage, dose homogeneity, and conformity. In IMRT, the coverage is better where PTV was overlapping with critical OARs.

Comparison of Carotid Artery Dose in Early-Stage Glottic Cancer Treated with 3D-Conformal, Helical-IMRT and VMAT

Abstract Background The aim of this study was to compare the dosimetry of carotid arteries (CAs) using three radiation therapy (RT) techniques, three-dimensional conformal RT (3D-CRT), helical tomotherapy-intensity-modulated RT (HT-IMRT), and volumetric modulated arc therapy (VMAT), in patients with early-stage glottic cancer. Patients and Methods A retrospective analysis of 28 patients was performed, and the right and left CAs were delineated. Mean and maximum dose (Dmax) values were compared across the three treatment techniques. Results The results indicate that 3D-CRT plans had the highest mean and maximum doses to CAs, while VMAT plans had the lowest doses. Conclusions Our study demonstrates the feasibility of sparing CAs with newer RT modalities. Further clinical studies are needed to determine if these techniques can reduce carotid stenosis-related events.

Dosimetric Study Comparing 3D Conformal Radiotherapy (3D-CRT), Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) in Hypofractionated One-Week Radiotherapy Regimen in Breast Cancer.

Introduction Recently, the one-week hypofractionated radiotherapy regimen (26 Gy in 5 fractions) for adjuvant breast radiotherapy has been shown to be non-inferior to other hypofractionated regimens (15-16 fractions). The aim of the present dosimetric study is to compare Intensity Modulated Radiotherapy (IMRT), Volumetric Modulated Arc Therapy (VMAT) and 3D Conformal Radiotherapy (3D-CRT) for a one-week hypofractionated radiotherapy regimen (26 Gy in 5 fractions) for adjuvant breast radiotherapy. Methods A total of 30 patients with histologically proven invasive carcinoma of the breast after breast conservation surgery (BCS) or modified radical mastectomy (MRM) were considered for in silico planning study. The dose prescription used was 26 Gy in 5 fractionsas used in the FAST Forward protocol. Targets were contoured according to standard guidelines. The heart, ipsilateral lung, and contralateral breast were contoured as organs at risk. Results Planning Target Volume (PTV) coverage:For IMRT, VMAT and 3D-CRT, respectively, the volumes that received at least 95% of the prescription dose (V95) were 95.7 ± 2.12, 92.47 ± 3.83, 90.87 ± 5.13; mean PTV doses (Dmean) were 26.1 ± 0.6, 25.7 ± 0.7, and 28 ± 4.39 (3D-CRT has higher Dmean compared to other techniques). Maximum PTV doses (Dmax) were 28.23 ± 0.72, 28.73 ± 0.64, and 29.8 ± 1.03. IMRT had a better V95 coverage and conformity index. Organs At Risk (OARs):The volumes that received at least 25% of the prescription dose (V25) of the heart were 3.41 ± 4.7, 1.8 ± 2.02 and 4.3 ± 6.98 in IMRT, VMAT and 3D-CRT, respectively. The volumetric (V25) comparison of heart dose in left-sided breast cancer was significantly different between VMAT and 3D-CRT (p=0.04, Wilcoxon signed-rank test). The volume that received at least 5% of the prescription dose (V5)was less than 25% in the 3D-CRT plan (12.55).For the ipsilateral lung, the V25 parameters were 19.53 ± 10.96, 23.93 ± 13.58 and 20.5 ± 12.32 in IMRT, VMAT and 3D-CRT, respectively. Conclusion From this study, we can conclude that IMRT and VMAT techniques are feasible and can achieve better dosimetric goals for target and OARs though minimizing the area achieving low dose remains to be a dosimetric concern for VMAT.

Volumetric modulated arc therapy (VMAT) comparison to 3D-conformal technique in lung stereotactic ablative radiotherapy (SABR).

Stereotactic ablative radiotherapy (SABR) can be a curative option for non-small cell lung cancer (NSCLC) and oligometastatic lung disease. Volumetric modulated arc therapy (VMAT) has offered further advancements in terms of radiation dose shaping without compromising treatment times however there is potential for greater low-dose exposure to the lung. This study was to assess whether VMAT lung SABR would result in any increase to the dosimetry parameters compared with three-dimensional conformal radiotherapy (3D-CRT) that could confer increased risk of radiation pneumonitis. A total of 53 and 30 3D-CRT treatment plans of patients treated with 48 Gy in 4 fractions were compared. No statistically significant difference in planning target volumes between the VMAT 29.9 cc (range 12.4-58.5 cc) and 3D-CRT 31.2 cc (range 12.3-58.3 cc) P=0.79. The mean of total lung V5, ipsilateral lung V5 and contralateral lung V5 all showed a trend of being smaller in the VMAT treatment group- 14% versus 15.8%, 25.6% versus 30.4% and 1.6% versus 2.2%, respectively, but all were not statistically significant differences. Mean of the mean lung dose MLD, again showed a trend of being lower in the VMAT treatments but was also non-significant, 2.6 Gy versus 3.0 Gy, P=1.0. Mean V20 was the same in both cohorts, 3.3%. The dosimetry for 3D-CRT and VMAT plans were not significantly different including V5, and therefore we conclude that VMAT treatment is unlikely to be associated with an increased risk of radiation pneumonitis.

Quality of Life Analysis of a Phase II Randomized Controlled Trial Comparing 3D-Conformal Radiotherapy (3D-CRT) and Intensity Modulated Radiotherapy (IMRT) in Locally Advanced Rectal Cancer (TRI-LARC)

<h3>Purpose/Objective(s)</h3> The aim of the study was to compare the use of 3D-CRT and IMRT in pre-operative long course chemo-radiotherapy for locally advanced rectal cancer. We herein evaluate the impact of the two treatment modalities on quality of life (QOL), a secondary objective of the study. <h3>Materials/Methods</h3> 94 patients with rectal adenocarcinoma were enrolled in a prospective randomized phase II trial across three institutions between 2014 and 2020. Eligible patients had stage T3-4, N(any) or circumferential resection margin at risk with no evidence of metastatic disease. All patients were prescribed 50.4Gy in 28 fractions with concomitant 5-fluorouracil or capecitabine. Patients were randomly assigned (1:1) to 3D-CRT and IMRT planning techniques. QOL was assessed using the EORTC QLQ C30 and QLQ CR29 questionnaires at baseline, during the final week of radiotherapy and at six and twelve months after radiotherapy. A paired sample t test was used to compare differences in QOL from baseline to each follow-up. One-way between-group analyses of covariance (ANCOVA) were conducted to compare the effect of the trial arms on each QOL score. <h3>Results</h3> At a median follow-up of 14 months, the trial was terminated early due to failure to establish efficacy in the primary outcome, acute gastrointestinal toxicity. The median age was 59 years and 72/94 (77%) were male. 86/94 (91%) patients completed the baseline and at least one other QOL assessments. QOL data at one year was available in 55/94(58%). At baseline, there was no difference in QOL scores between trial arms. Overall, emotional functioning had improved at six months but physical, cognitive, role and social functioning had declined. At six months, there was a significant improvement in constipation, blood and mucous in stool, bloating, urinary frequency, buttock pain and anxiety scores compared to baseline. There was a significant deterioration in dyspnea, fatigue, nausea/vomiting, taste, hair loss, erectile dysfunction, body image and global health scores from baseline to 6-month follow-up. After adjusting for pre-intervention score, the IMRT arm had better physical functioning (p=0.038) and role functioning (p=0.014) during the final week of radiotherapy compared to the 3DCRT arm. The end of radiotherapy embarrassment score, for those without a stoma, was significantly worse in the IMRT arm (p=0.032). There was no other significant difference in QOL scores between the two arms, at either the final week of radiotherapy or at 6 months, after adjustment for pre-intervention scores. The limitations of the study include its early termination, the potential for type 1 error and the possible influence of other factors on QOL data such as chemotherapy and postoperative complications. <h3>Conclusion</h3> There are limited QOL benefits of IMRT compared to 3D-CRT in the neoadjuvant setting for rectal cancer.

3D-CRT, IMRT and VMAT for flank irradiation due to pediatric Wilms tumor: A comparative planning study with XCAT phantoms

PurposeTo compare the dosimetric parameters and radiogenic risks from 3D-CRT, IMRT and VMAT for flank irradiation due to pediatric Wilms tumor. MethodsTwo computational XCAT phantoms simulating an average 5- and 10-year-old patient were used. Four different planning target volumes (PTVs) for right flank (RF) and left flank (LF) irradiation with or without paraaortic lymph nodes (LNs) and eight surrounding organs-at-risk (OARs) were contoured on the phantoms’ CT sections. Forty-eight 3D-CRT, IMRT and VMAT plans were created using 6 and 10-MV photons on the two phantoms. The target coverage index (TCI), homogeneity index (HI), conformity index (CI), conformation number (CN) and OAR exposure were determined through dose-volume histogram (DVH) analysis. Second cancer risks were estimated using a non-linear model and DVH data. ResultsThe IMRT and VMAT for LF + LN and RF + LN irradiation reduced the radiation dose to four to six out of the eight OARs compared to 3D-CRT. Conventional treatment provided a better organ sparing for RF and LF irradiation. The IMRT and VMAT led to superior planning parameters in respect to 3D-CRT for all PTVs and both patient’s ages (3D-CRT: TCI = 59.80 % - 82.26 %, CI = 0.55–0.81, CN = 0.40–0.64, HI = 1.11–1.15; IMRT: TCI = 96.04 % - 99.72 %, CI = 0.85–0.91, CN = 0.85–0.88, HI = 1.03–1.05; VMAT: TCI = 96.02 % - 99.69 %, CI = 0.86–0.91, CN = 0.85–0.89, HI = 1.03–1.06). The excess-absolute-risk for developing secondary small intestine, liver and stomach malignancies from 3D-CRT were (7.99–19.32) × 10-4, (0.29–3.83) × 10-4 and (0.37–4.50) × 10-4 persons-year, respectively. The corresponding risks from intensity modulated techniques reached to 22.26 × 10-4, 4.58 × 10-4 and 5.42 × 10-4 persons-year. ConclusionsThis dataset related to plan quality, radiation dose and risks to OARs allows the selection of the proper treatment technique for flank irradiation based on the patient’s age and target site.