3D Conformal Plans Research Articles

Establishment of local diagnostic reference levels for breast cancer CT protocols in radiotherapy in a single Moroccan center

The objective of this study was to establish local diagnostic reference levels (LDRLs) for breast cancer computed tomography imaging in radiotherapy (CT-RT) at a single hospital in Morocco. Data were collected from 106 adult breast cancer patients aged between 33 and 78 yr during five months. Data were obtained using a Hitachi Supria 16-slice CT simulator at a regional oncology center in Morocco. CT-RT images are intended for 3D conformal radiotherapy treatment planning. Dose length product (DLP) and volumetric computed tomography dose index (CTDIvol) were evaluated by determining the 75th percentile as diagnostic reference levels for CT-RT breast cancer. LDRLs for CT-RT breast cancer have been determined in terms of DLP and CTDIvol, and they were 330.4 mGy.cm and 6.8 mGy, respectively. The DRLs were compared with other Europeans study. DRLs for this study were lower than those for the United Kingdom (UK), Croatia and Slovenia. The results of this study can be a reference for the establishment of local and national DRLs in Morocco and the optimization of CT-RT breast cancer procedures.

A Novel Setup Technique for Radiation Treatment of a Severely Obese Patient With a Primary Brain Tumor.

Modern external beam radiation therapy (EBRT) techniques rely on the accurate positioning of the patient using the treatment couch. These motorized couches have weight limits that have decreased over time and are not able to support severely obese patients requiring EBRT. We aimed to develop a technique to support obese patients who are above their weight tolerance while accurately delivering radiation treatment to a brain tumor. This technique was used on a patient receiving adjuvant radiation for gliosarcoma, a variant of glioblastoma. The patient was CT scanned, and the 3D conformal radiation therapy plan was created. A custom treatment couch was created using a transport stretcher, Styrofoam, a CT couch-top, and an IMRT board, which allowed for a thermoplastic mask to be used for a reproducible setup. AP and lateral portal films were taken prior to each treatment to confirm the accuracy of the manual daily setup of the patient on the custom couch. The patient received 60 Gy in 30 daily fractions of 3DCRT in a reproducible fashion. The average deviation from the isocenter fell within the 10 mm and 8 mm planning margins applied to the clinical target volume (CTV) for the initial and boost fields, respectively. The average daily shifts in the anterior-posterior (AP) direction for the patient were 7.97 (-16.19 to 12.04) mm and 1.98 mm (-1.1 to 4.3) mm for the initial and boost treatments, respectively. The average daily shifts in the superior-inferior (SI) direction were 2.2 (-5.08 to 9.04) mm and 3.88 (-2.9 to 8.0) mm for the initial and boost treatments, respectively. This novel approach allowed treatment at 60 Gy for a gliosarcoma patient who had previously been denied treatment due to his weight. By utilizing readily available materials within the department, our team was able to create a reproducible setup technique to safely treat the patient.

Abstract ED8-1: Overview of the current state of the art – what patients and oncologists need to know

Abstract While radiation therapy plays a significant role in the treatment of breast cancer for many patients, the nuances of modern day radiation therapy are often poorly understood by both patients and referring providers. Radiation therapy techniques to reduce toxicity and improve treatment accuracy have rapidly evolved in the past decade. This session will introduce non-radiation oncologists to recent innovations that allow increased personalization of treatment based on anatomical variations. Methods to improve patient positioning will be discussed. Frequently utilized dosimetric techniques for breast radiotherapy will be described and compared, including Volumetric Modulated Arc Therapy (VMAT), Intensity Modulated Radiation Therapy (IMRT), and 3D conformal planning. New methods for patient monitoring during treatment and the purpose of respiratory gating will be reviewed. Finally, the impact of surgical therapies on radiation planning and delivery will also be examined. Attendees should leave the session having a greater understanding of the current available options for radiotherapy and rationale for the choice of treatment technique. Citation Format: Rachel Jimenez. Overview of the current state of the art – what patients and oncologists need to know [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr ED8-1.

Different meaning of the mean heart dose between 3D-CRT and IMRT for breast cancer radiotherapy.

Previous studies in 2D and in 3D conformal radiotherapy concludes that the maximal heart distance and the mean heart dose (MHD) are considered predictive of late cardiac toxicities. As the use of inverse-planned intensity modulated radiation therapy (IMRT) is increasing worldwide, we hypothesized that this 3D MHD might not be representative of heart exposure after IMRT for breast cancer (BC). Patients with left-sided BC and unfavorable cardiac anatomy received IMRT. Their treatment plan was compared to a virtual treatment plan for 3D conformal radiotherapy with similar target volume coverage (study A). Then, a second 3D conformal treatment plan was generated to achieve equivalent individual MHD obtained by IMRT. Then the heart and left anterior descending (LAD) coronary artery exposures were analyzed (study B). Last, the relationship between MHD and the heart volume or LAD coronary artery volume receiving at least 30Gy, 40Gy and 45Gy in function of each additional 1Gy to the MHD was assessed (study C). A significant decrease of heart and LAD coronary artery exposure to high dose was observed with the IMRT compared with the 3D conformal radiotherapy plans that both ensured adequate target coverage (study A). The results of study B and C showed that 3D MHD was not representative of similar heart substructure exposure with IMRT, especially in the case of high dose exposure. The mean heart dose is not a representative dosimetric parameter to assess heart exposure following IMRT. Equivalent MHD values following IMRT and 3DRT BC treatment do not represent the same dose distribution leading to extreme caution when using this parameter for IMRT plan validation.

Cost of Care Related to Treatment of Bone Metastases: Real World Data from a National Health Insurance Provider

<h3>Purpose/Objective(s)</h3> Bone metastases are a common occurrence in patients with advanced stage malignancy, often impacting quality of life. Radiation has been, and remains, a highly effective modality for the treatment of symptomatic bone metastases. Various radiation fractionation schemes and techniques exist and are used across the United States in these patients. The cost of care presumably varies significantly based on those factors (technique and number of fractions). We accessed payer claims data from a health insurance provider in Pennsylvania, Delaware, and West Virginia to help determine the actual cost of care for patients with bone metastases treated with radiation. <h3>Materials/Methods</h3> This study was a secondary data analysis of medical claims data using a retrospective design among insured members in Pennsylvania, Delaware, and West Virginia with an ICD-10 code of C79.51 and history of radiation therapy billed under that code from 1/1/2016 to 9/30/2021. Patients were grouped by age, sex, and geographical region. Number of claims and total cost of care were tabulated by year. We also examined which radiation technique was used (intensity modulated radiation therapy (IMRT) vs. 3D conformal radiotherapy (3D CRT) vs. complex isodose plan) based on CPT codes. Lastly, we looked at the use of image guided radiation therapy (IGRT) over that same time period, again using CPT codes. <h3>Results</h3> We identified 29,201 patients treated with radiation for diagnosis code C79.51 between 2016 and 2021. The median number of claims per year was 4,866 (2,744-6,000). Fifty-one percent of patients were male (13,676). The majority of patients (79%) resided in Pennsylvania. The median total cost of care related to ICD-10 C79.51 was $181,918,217 ($163,672,315-$183,565,407). The median number of claims for those years was 95,024 (89,870-101,449). The number of claims per patient varied from 2.3-5.0 and 3.5-10.2 for isodose complex treatment and IMRT, respectively. Most patients were treated using isodose complex technique or 3D CRT (combined 80-90%) with a relatively even split. The use of IMRT remained relatively stable over the timeframe (5-15%). The use of IGRT increased over time, with highest number of claims for IGRT being 2020 (458 claims) (median 266, range: 183-458). The median cost per year for all care related to ICD10 C79.51 was $10,887,581, $7,274,264, and $1,902,141 for patients treated with 3D CRT, IMRT, and isodose complex, respectively. <h3>Conclusion</h3> Radiation remains a widely used technique for the palliation of bone metastases. The cost of care related to its use are significant. The use of IGRT increased over time, with no obvious impact on overall cost of care. The use of IMRT remained low for bone metastases, with an associated increase in cost of care. The overall cost of care remained lowest for those patients treated with isodose complex treatment.

Improving Radiation Quality Through the Implementation of Prospective Peer Review

<h3>Purpose/Objective(s)</h3> Quality assurance (QA) is critical to the successful delivery of radiation therapy (RT) for cancer patients and also impacts outcomes. The present study reports the longitudinal results of a prospective peer review evaluation system (PES) implemented at a major academic health system as an integral part of RT QA. <h3>Materials/Methods</h3> All patient cases treated with RT by one of 32 physicians at 14 treatment locations within our radiation oncology department undergo prospective peer review in daily rounds. Each case is assigned a grade (A, B, C) based on the following criteria: clinical suitability for RT, prescription, contours, and treatment plan, where applicable. "A" cases require no changes, "B's" require minor modification, and "C's" require major modification with re-review prior to treatment planning. The present study is a longitudinal analysis of grade trends over time by hospital, plan type, and physician. The Wilcoxon-signed-ranked test was used to compare grades during the baseline PES period (2013-2016) to the follow-up period (2017-2021). A p-value below 0.05 is considered significant. <h3>Results</h3> A total of 20,069 cases for 14,300 patients were reviewed from September 2013 to November 2021. Of the total cases, 15,659 (78%) were curative and were included in the present analysis; 5,868 from the baseline period and 9,791 in the follow-up period. The fraction of A cases decreased from 74.8% (baseline) to 64.5% (follow-up), while the fraction of B's increased from 19.4% (baseline) to 35.4% (follow-up), and the fraction of C's decreased from 5.8% (baseline) to 0.1% (follow-up). The main hospital site contributed 54.8% of all cases and 48.1% of all B grades. IMRT plans accounted for 55.4% of all plans and 68.2% of all B scores, while 3D-conformal plans accounted for 24.4% of cases and 15.4% of all B scores. When normalized by total department A/B/C scores, there were no statistically significant changes in percent A/B/C scores over the time period studied (p-value> 0.05). However, for the 13 physicians with cases throughout the study period, there was a statistically significant increase in the fraction of B scores (p value = 0.01) and decrease in the fraction of C scores (p value < 0.01) between the two time periods when individual physician grades were normalized to their individual caseload. <h3>Conclusion</h3> PES improves the identification of quality-related factors that can impact downstream radiation treatment plan quality. The diminishing fraction of C grades over time indicates amelioration of ‘major failures,' which were addressed in the startup years of PES. The proportional increase in B's, at the cost of fewer putative A's, suggests increased scrutiny of cases, as well as findings-based improvements in contouring and planning, over time. Peer review rounds upstream of treatment planning provides valuable RT QA and should be considered by other departments to enhance the quality and consistency of RT.

Verification of monitoring unit calculations for the 3D conformal radiotherapy treatment planning system

The present work aims to validate an Independent Calculation of Monitoring Units (ICMU) software developed to accurately calculate the number of Monitoring Units (MU) used in radiation treatment. The calculation was performed for the photon beam with a variety of nominal energies (6 MV − 18 MV) and filed size ranging from 3 × 3 cm2 to 40 × 40 cm2. Two set-up conventions of treatment techniques were tested, a constant source to surface distance (SSD) and an isocentric set-up with a constant source to axis distance (SAD). The ICMU software was written in C-sharp (C #), using the equivalent square field size concept to calculate the radiation field quantities and connects to a database containing measurements quantities such as Tissue Phantom ratio (TPR) and Output Factors (OFs). The ICMU was successfully validated by comparing it to the Treatment Planning System (TPS) or CMS Monitor Unit Calculations (CMS_MU). The required standards were satisfactorily met (5.0%).

Precision radiotherapy by SPECT lung functional imaging in NSCLC

Background: Single Photon Emission Computed Tomography (SPECT) could be used to avoid the non-affected perfusion areas in patients with non-small-cell lung cancer (NSCLC) and to potentially reduce lung toxicity. The aim of this study is to compare dosimetric differences between two different 3D-conformal treatment plans, with and without CT/SPECT contribution. Methods: Simulation Computed tomography (CT) scans were accurately co-registered with SPECT scans and three different areas, based on SPECT intensity perfusion, were contoured: low perfusion (LP), medium perfusion (MP) and high perfusion (HP). Two different 3D-conformal plans, with co-planar and nonco-planar fields, were generated; one without SPECT information (anatomic plan), and one using the perfusion area identified with functional imaging (functional plan). Results: 9 patients were planned and a total of 18 plans were available for analysis. Anatomical and functional plans resulted in comparable planning target volume (PTV) coverage. In the functional plans, a significant reduction of dose in high perfusion areas was reported. The reduction of HP-V20 Gy values ranged from 15% to 8% (p = 0.046), the ipsiHP-V20 Gy from 38% to 22% (p = 0.028) and ipsiHP-Dmean reduction from 16 Gy to 12 Gy (p = 0.039). No significant differences in other organs at risk (OARs) metrics were reported between anatomical and functional plans. Conclusions: Despite the few cases reported, the strength of our study lies in the reported benefit of functional lung information in 3D conformal radiation planning, without compromising target coverage or worsening dose distribution to the OARs. There is an urgent need for prospective clinical and randomized trials in order to define the role of lung functional imaging in reducing toxicity in clinical practice.

Evaluation of Doses to Target Volume and Organs at Risk by Conventional versus RTOG Contouring Based 3D Conformal Plans in Breast Cancer: A Prospective Study

Introduction: In radiotherapy, conventional field borders have often little anatomical correlation with the draining lymphatics. So, with the availability of more conformal techniques and delineation guidelines, an evident need exists to optimise our treatment plans with more focus on planning and dosimetric aspects. Aim: To evaluate the differences in dosimetric parameters to the Organs at Risk and target volumes in patients treated with conventional plans vis-à-vis Radiation Therapy Oncology Group contour guided treatment plans. Materials and Methods: A prospective interventional study was conducted in which 30 patients of histopathologically proven Infiltrating Ductal Carcinoma (IDC) breast, with age range of 18 to 80 years were enrolled. Patients were treated with 50 Gray in 25 fractions of radiation with additional 10 Gray in 5 fractions boost in Breast Conserving Surgery (BCS) patients by conventional treatment plans. Radiation Therapy Oncology Group (RTOG) guidelines were used for breast/Chest Wall (CW), axillary nodes, Supraclavicular Fossa (SCF), and Internal Mammary Node (IMN) delineation. Organs At Risk (OARs) included heart, Ipsilateral (I/L) lung, Contralateral (C/L) breast, oesophagus and spinal cord. Dose-Volume Histograms (DVHs) for these contours were generated from conventional treatment plans. Further, new treatment plans were generated to cover &gt;90% of Planning Target Volume (PTV) by 90% isodose line. DVH parameters of these two plans were compared using paired t-test. A p-value of &lt;0.05 was considered statistically significant. Results: Of the total 30 cases, the mean volume of breast/CW PTV covered by 90% isodose line (V90) was better in RTOG plan as compared to Conventional plan (93.39 vs 90.39, p-value=0.001). Similarly, mean V90 for total axilla (97.44 vs 90.39, p-value=0.0001) and combined PTV (92.60 vs 88.81, p-value=0.0001) was better with RTOG plan. For OARs, conventional vs RTOG plans; Dmean for heart was 2.56 vs 2.60Gy, p-value=0.63), I/L lung V20Gy was 28.77 vs 28.94%, p-value=0.71) and V5Gy for C/L breast was 0.48 vs 0.54%, p-value=0.47), respectively. In cases where IMN was irradiated, mean doses to the heart, I/L lung V20Gy, and contralateral breast V5Gy increased significantly. Conclusion: The present study showed that RTOG target volumes had inadequate coverage in conventional plans. On the contrary, plans directed at RTOG contours provided statistically better coverage for target volumes without increase in the doses to the OARs. In patients with IMN irradiation, the doses to some OARs were increased in RTOG as compared to conventional plans.

A Dosimetric Analysis of Incidental Radiation to the Internal Mammary Nodes with a Three-field Chest Wall Technique

Objectives: The authors’ aim was to conduct a dosimetric analysis of the incidental radiation dose to the internal mammary node (IMN) region using a three-field chest wall technique (TFCWT). Methods: This retrospective study utilized 3D-conformal radiotherapy plans of 50 post-mastectomy patients (25 left-sided and 25 right-sided). All plans used the TFCWT, composed of narrowed tangents matched medially to an AP electron field, and prescribed a total dose of 50 Gy in 28 fractions. The IMNs were not intentionally treated in all included plans. Results: The mean dose to the IMN-planning target volume (IMN-PTV) was 45.1 Gy (26.4 - 55.6, SD 6.5). Minimum doses received by 95% and 90% of the IMN-PTV were 29.3 Gy (8 - 49, SD 10.0) and 34.0 Gy (10.0 - 52.0, SD 8.6), respectively. The percent volume of IMN-PTV receiving 100%, 95%, 90%, and 80% were 47.4% (3 - 94, SD 21.6), 55.6% (6 - 97, SD 22.4), 61.92% (7 - 98, SD 22.2), and 72.61% (18-100, SD 20.2), respectively. The average ipsilateral lung V20 Gy (with supraclavicular fields) was 25.0% (16 - 29, SD 3.4), and the average heart mean dose was 2.5 Gy (0.5 - 7.9, SD 1.58). Conclusion: Although the results suggest increased IMN radiation doses with the TFCWT when compared historically to standard tangents, the incidental doses are comparatively less than that traditionally prescribed to the IMNs in high-risk patients. It is unknown whether this incidental IMN dose confers any clinical benefit.

Secondary cancer risk after radiotherapy of seminoma stage one

Background: In radiation treatment of stage one seminoma (SOS) induced secondary cancer in organs at risk (OARs), located in or out of the radiation fields, is a late toxicity of major concern. This study aimed to compare the secondary cancer risk in radiotherapy of SOS in two-dimensional conventional radiation therapy (2D) and three-dimensional conformal radiation therapy (3DCRT). Materials and Methods: CT scan images of 10 patients with SOS were used to design 2D conventional and 3D conformal treatment plans using 25 Gy in 20 sessions. The life attributable risk (LAR) of liver, stomach, and colon were calculated using the organ equivalent dose (OED) model for organs in radiation field and Biologic Effects of Ionizing Radiation VII (BEIR VII) model for organs out of field. Results: LAR of OARs in radiation field such as, liver and stomach was obtained 40% higher in the 2D treatment than in the 3D treatment, while as for the colon, it was 17% lower in the 2D treatment than in the 3D treatment. The LAR values of kidneys located outside the radiation field in the 2D treatment were calculated 0.04%. Conclusion: Increasing the prescribed dose (25 vs. 20) as well as the number of treatment sessions (20 vs. 10) resulted in increasing in the LAR of at-risk organs such as liver, stomach, colon. Therefore, estimating cancer risk of critical organs exposed to radiation through examining the effects of dose fractionation and prescribed doses can be used in optimizing of treatment plan for seminoma, selection of a better treatment method by oncologists, and patient follow-up.

COVID-19 in Sub-Saharan Africa: A Multi-Institutional Survey of the Impact of the Global Pandemic on Cancer Care Resources

Purpose/Objective(s)The COVID-19 pandemic has direct and indirect impact on patients with cancer. Low- and middle-income regions, especially sub-Saharan Africa, are especially vulnerable to a negative impact on cancer resources and outcomes. We report the initial indirect impact of COVID-19 on cancer care in the sub-Saharan Africa region approximately 14 months into the pandemic.Materials/MethodsAt the start of the pandemic, we created a consortium of African and North American cancer centers and NGOs for the distribution of factual and timely information and data on COVID-19 and cancer care. A survey was distributed to consortium members and other colleagues from the sub-Saharan Africa region to understand the impact of COVID-19 in cancer care resources. Survey respondents represent cancer experts from 8 centers in Ghana, Nigeria, Kenya, Ethiopia, South Africa, Rwanda, and Zimbabwe.ResultsAll sites report SARS-COv-2 transmission amongst cancer patients and staff. A total of 48 staff developed COVID-19 infection with one site reporting a single death. Additionally, 62.5% of sites report loss of oncology physician or nursing staff due to redeployment for COVID-19 care resulting in minimal (20%), moderate (60%), or other (20%) impact on cancer care. All 8 sites report a government mandated lockdown with a median duration of 2.3 months (IQR .9-4.2 months). Impact of the lockdown on cancer care was reported as none (12.5%), minimal (12.5%), moderate (50%) and severe (25%). Additionally, we surveyed the impact of COVID-19 on resources in radiation, medical and surgical oncology services. A total of 25% of responders reported decreases in radiation resources while 37.5% reported changes in medical and surgical oncology resources. For radiation oncology, the most common impact was access to CT imaging for 3D-conformal planning (25%), access to brachytherapy (12.5%), and medical physics support (12.5%). For medical oncology, the most frequent impact was access to chemotherapy (37.5%) and blood products (12.5%), and loss of oncology ward space (12.5%). The most frequent impact for surgical oncology was access to operating rooms (37.5%), ventilators (12.5%), anesthesia (25%), blood products (25%), and other supply chain issues (25%). Of centers who reported impact on cancer care, severity of impact was none (50%) and moderate (50%) for radiation oncology; mild (25%) and moderate (75%) for medical oncology; and moderate (75%) and severe (25%) for surgical oncology.ConclusionOur survey identified diffuse impact of COVID-19 on all facets of cancer care across sub-Saharan Africa. Based on physician assessment of impact, the discipline of surgical oncology may be impacted the greatest. Additional studies measuring the impact of COVID-19 on cancer outcomes are ongoing.

Implementation of 3D conformal radiotherapy technology at the National Cancer Centre Mongolia: A successful Asia-Pacific collaborative initiative.

Mongolia has a population of 3.3 million and is classified by the WHO as a lower middle-income country. Cancer is now a major public health issue and one of the leading causes of mortality. Within the framework of an existing national cancer control plan, the National Cancer Centre of Mongolia (NCCM) aimed to implement 3D conformal radiation planning and linac-based treatment delivery. In 2018, anopportunityarose for collaboration between the Mongolia Society for Radiation Oncology (MOSTRO), the National Cancer Centre Mongolia (NCCM), the Asia-Pacific Radiation Oncology Special Interest Group (APROSIG) of the Royal Australian and New Zealand College of Radiologists (RANZCR) and the Asia-Pacific Special Interest Group (APSIG) of the Australasian College of Physical Scientists and Engineers in Medicine (ACPSEM) and radiation therapists (RTTs) from a range of Australian centres. We describe here the results to date of this collaboration. Despite a number of significant technical and practical barriers, successful linac commissioning was achieved in 2019. Key factors for success included a leadership receptive to change management, stable bureaucracy and health systems, as well as a synchronised effort, regional cooperation and mentorship. Future directions for ongoing collaborative efforts include a continued focus on education, practical training in radiotherapy planning and delivery and postgraduate education initiatives. Radiotherapy safety and quality assurance remain an ongoing priority, particularly as technological advances are sequentially implemented.

Dosimetric study on the use of Eclipse beam angle optimiser for conformal planning

AbstractAim:The aim of this study was to evaluate the use of Eclipse’s beam angle optimiser (BAO) for three-dimensional conformal radiotherapy planning.Materials and methods:Eleven 3D conformal lung plans, with varied tumour volumes, were retrospectively studied. For each clinical plan, a BAO plan was produced and then optimised by an experienced planner. Plan quality was assessed using International Commission on Radiation Units and Measurements (ICRU)-83 and Radiation Therapy Oncology Group (RTOG) recommended dose reporting metrics for dose volume prescribing and reporting.Results:Differences in dose volume histograms for both methods showed no clinical significance. Planning target volume Dmax for both plans was comparable and within ICRU guidelines. Reported spinal cord Dmax and the doses to 33% and 67% volume of the heart were within the RTOG recommended limits. Mean lung V20 values for BAO and non-BAO plans were 20 and 16%, respectively. The average monitor units for the BAO plans were about 11% lower. The conformity and homogeneity indices were within the acceptable range for both cases. On average, it took 23 minutes to plan using the BAO compared to 68 minutes for the non-BAO plans.Conclusion:Eclipse BAO shows the potential to produce good quality conformal plans and reduce planning time. This process could be further refined with multi-leaf collimator and optimal collimator angle options.

Dosimetry comparison and evaluation of 3D and IMRT for left breast cancer radiotherapy techniques treated at ain wazein medical village hospital in Lebanon

Breast cancer patients undergoing radiation therapy can be treated using the 3D conformal or VMAT techniques. For both plans, the doses received by the target and the organs at risk are determined and compared with protocols recommended for the safety of the patients. CT simulations of 10 women with left breast cancer were used for a 3D conformal and VMAT treatment plans in the radiotherapy department of Ain Wazein Medical Village Hospital (AWMV) utilizing Monaco Treatment Planning system using Collapsed-cone and Monte Carlo algorithms respectively. The total prescribed dose to the PTV was 50 Gy in 25 fractions each 2 Gy. The dosimetric parameters obtained were mean, D95%, and homogeneity index for PTV; mean dose and max doses for the heart; the V20% for the left and the right lungs. All values of this retrospective study were analysed and compared to the normal tissue maximum dose tolerance. VMAT plans resulted in significantly better coverage for the target volume concepts as compared with 3D-CRT (D95: 97% vs. 82%, p-value = 0.002; Dmean 4953 cGy in 3D-CRT vs. 5093 cGy in VMAT, p-value = 0.01). The left lung (V20:28.44% with 3D-CRT vs. 21.93 with VMAT, p-value = 0.02). For the heart (Dmax = 4919 cGy in 3D-CRT vs. 4617 cGy in VMAT, p-value = 0.07). For the right lung (V20 was 0.12% in 3D-CRT vs. 0.52% in VMAT with p-value = 0.008). Even though the p-value was significant for the 3D conformal technique, the dose for both techniques was very low and non-significant to have a risk in the organ. The VMAT technique with correct target volume delineation allowed a significant dose escalation and an increase in Tumor Control Probability (TCP). VMAT resulted in an improved sparing of OARs as compared with 3D-CRT at equivalent dose levels.

Ninjaflex vs Superflab: A comparison of dosimetric properties, conformity to the skin surface, Planning Target Volume coverage and positional reproducibility for external beam radiotherapy.

Background and purposeWhen planning and delivering radiotherapy, ideally bolus should be in direct contact with the skin surface. Varying air gaps between the skin surface and bolus material can result in discrepancies between the intended and delivered dose. This study assessed a three‐dimensional (3D) printed flexible bolus to determine whether it could improve conformity to the skin surface, reduce air gaps, and improve planning target volume coverage, compared to a commercial bolus material, Superflab.Materials and methodsAn anthropomorphic head phantom was CT scanned to generate photon and electron treatment plans using virtual bolus. Two 3D printing companies used the material Ninjaflex to print bolus for the head phantom, which we designated Ninjaflex1 and Ninjaflex2. The phantom was scanned a further 15 more times with the different bolus materials in situ allowing plan comparison of the virtual to physical bolus in terms of planning target volume coverage, dose at the prescription point, skin dose, and air gap volumes.ResultsSuperflab produced a larger volume and a greater number of air gaps compared to both Ninjaflex1 and Ninjaflex2, with the largest air gap volume of 12.02 cm3. Our study revealed that Ninjaflex1 produced the least variation from the virtual bolus clinical goal values for all modalities, while Superflab displayed the largest variances in conformity, positional accuracy, and clinical goal values. For PTV coverage Superflab produced significant percentage differences for the VMAT and Electron3 plans when compared to the virtual bolus plans. Superflab also generated a significant difference in prescription point dose for the 3D conformal plan.ConclusionCompared to Superflab, both Ninjaflex materials improved conformity and reduced the variance between the virtual and physical bolus clinical goal values. Results illustrate that custom‐made Ninjaflex bolus could be useful clinically and may improve the accuracy of the delivered dose.

Cardiac dose reduction using deep inspiratory breath hold (DIBH) in radiation treatment of left sided breast cancer patients with breast conservation surgery and modified radical mastectomy

PurposeDeep inspiration breath hold (DIBH) reduces heart and pulmonary doses during left-sided breast radiation therapy (RT); however, there is limited information whether the reduction in doses is similar in patients with modified radical MRM (MRM) and breast conservation surgery (BCS). The primary objective was to determine whether DIBH offers greater dosimetric reduction in cardiac doses in patients with MRM as compared to BCS with secondary objectives of documenting time consumed in counseling, simulation and planning such techniques. MethodsThirty patients with diagnosis of left sided breast cancer underwent CT simulation both free breathing (FB) and DIBH. Patients were grouped into two cohorts: MRM (n = 20) and BCS (n = 10). 3D-conformal plans were developed and FB was compared to DIBH for entire group (n = 30) and each cohort using Wilcoxon signed-rank tests for continuous variables and McNemar's test for discrete variables. The percent relative reduction conferred by DIBH in mean heart (Dmean heart) and left anterior descending artery dose (LADmean and LADmax), heart V25,V10, V2 and ipsilateral DmeanLung,V20, V12 were compared between the two cohorts using Wilcox rank-sum testing. A two-tailed p-value ≤ 0.05 was considered statistically significant. Time consumed during FB and DIBH from patient counseling to planning was documented. ResultsPatients undergoing BCS had comparable boost target coverage on DIBH and FB. For the overall group (n = 30), DIBH reduced Dmean heart and LAD dose, V25, V10 and V2 doses for the heart and Ipsilateral DmeanLung, V20, V12 which was statistically significant. For individual cohorts DIBH did not significantly reduce the lung (Ipsilateral DmeanLung, V20, V12) and LAD (LADmean and LADmax) doses for BCS while significant reduction in all cardiopulmonary doses was seen in MRM cohort. Despite significant reductions with DIBH in MRM, ipsilateral lung constraint of V12 < 15% was less commonly achieved in MRM (n = 11, 55%) requiring nodal radiation as compared to BCS (n = 3, 30%). Percent reduction in all cardiac and pulmonary dosimetric parameters with DIBH was similar in the MRM cohort as compared to BCS cohort. In total 73.1 ± 2.6 min was required for FB as compared to 108.1 ± 4.1 min in DIBH. ConclusionDIBH led to significant reduction of cardiac doses in both MRM and BCS. Reduction of lung and LAD doses were significant in MRM cohort. All cardiac constraints were met with DIBH in both cohorts, lung constraints were less frequently met in MRM cohort requiring nodal radiation.

Dosimetric analysis of normal tissue toxicity in 3D conformal radiotherapy planning with fused PET-CT imaging in non-small cell lung carcinoma

Introduction: The prime modality for inoperable NSCLC is radiation therapy and or chemo-radiation and better results can be achieved by a higher dose of radiation. However dose escalation is difficult due to presence of critical and dose limiting sensitive structures in the vicinity of lung. Therefore success of radiotherapy in such tumors solely depends on the selective delivery of adequate dose to target with minimal irradiation of surrounding structures. The precision in target and normal tissue delineation needs to be achieved. So the aim of this study is to explore the possibility of using fused PET-CT images for accurate target and normal tissue delineation in 3D-conformal radiotherapy planning in patients of carcinoma lung (NSCLC) who are referred to us for radical radiotherapy. Materials and Methods: It’s a hospital based prospective study in which 14(n) cancer patients who had biopsy proven NSCLC and were referred to us for radical radiotherapy. After CT simulation and FDG-hybrid PET data sets were transferred to CMS planning system. The co-registration was done in Focal Pro using an auto fusion, 3D rotation and translation rigid body program, and the fiducial markers. The gross tumor volume (GTV), planning target volume (PTV) and normal tissue parameters were defined using the CT data and PET-CT data. 3D-CRT plans were generated for both CT data and PET-CT data sets and dosimetric analysis was done for same. Results: The mean age was 65 yrs, 78.5% (11) patients are male and 21.5 % (3) are female. The registration of fused images of PET with planning CT scan decreased the gross tumor volume (GTV) in 10 patients (71.42%), decreased volume in 4 patients (28.58%). The 3D-CRT planes were modified in 5patients (35%). CT-PET planning did not reduce the radiation fields in all patients. When all constraints of the lung, esophagus, and spinal cord were taken into account, normal tissue exposure was reduced with use of CT-PET. V20 decreased from 31.86% ± 4.17% to

Post-Mastectomy Radiation Therapy after Prepectoral Breast Reconstruction Is Associated with A Low Early Explantation Rate

Immediate breast reconstruction with a prepectoral tissue expander (TE) in women who require mastectomy is associated with reduced postoperative pain due to avoidance of muscle dissection and elimination of breast animation deformity. Outcomes of patients with immediate prepectoral breast reconstruction who undergo post-mastectomy radiation therapy (PMRT) are not well studied. We report on cellulitis and explantation rates for breast cancer patients receiving mastectomy with immediate prepectoral breast reconstruction followed by PMRT at a single institution. Patients with breast cancer who underwent mastectomy with immediate prepectoral breast reconstruction and PMRT at our institution with at least 6 months of follow up were included. Demographic data, disease and treatment characteristics, and outcomes were collected. Sixteen patients met inclusion criteria. Median age was 49 years (IQR 41.2-54.9) and median follow up after PMRT was 14.8 months (range 5.7–36.6). All patients except 1 received chemotherapy. Surgical incisions included periareolar (38%), inframammary (31%), transverse (25%), and Wise pattern (6%). All patients underwent acellular dermal matrix placement during surgery. Median time to PMRT from surgery was 88 days (IQR 68-187). All patients received 50Gy in 25 fractions, except 1 received 42.56Gy in 16 fractions on a prospective clinical trial. Ten patients were treated with 3D conformal plans and 6 with intensity modulated radiation therapy plans. Thirteen (81%) patients had no acute complications. Three patients developed cellulitis during PMRT; 2 (13%) of these patients had a history of cellulitis prior to PMRT and developed recurrent cellulitis during treatment, requiring admission with intravenous antibiotics for 2 and 4 days, respectively, and oral antibiotics for the duration of PMRT. One required TE explantation 5 months later and the others had no further complications. Seven (44%) patients underwent TE removal with permanent silicone implant placement at a median of 7.2 months (range 4.9-8.8) after PMRT. Four (25 %) patients elected to undergo autologous reconstructions subsequent to PMRT and 2 (13%) patients elected for TE removal without reconstruction. Two (13%) patients have completed PMRT but have not yet had reconstruction. No patients experienced loss of their permanent implant at time of last follow up. In this small single institution series, we found that patients who undergo PMRT after prepectoral breast reconstruction do not appear to be at higher risk for infection. Grade 3 skin infection only occurred in patients with previous history of infection prior to radiation and those patients should be monitored closely during PMRT. The majority of patients with prepectoral breast reconstructions appear to be able to proceed to second stage permanent implant. The overall loss of implant rate was 6% in this small series though longer follow-up is needed.

On the feasibility of absolute 3D dosimetry using LiF thermoluminescence detectors and polymer gels on a 0.35T MR-LINAC

Background and Purpose. As shown in our previous study, highly accurate absolute dosimetry in 3D is feasible by combining polymer gels (PG) with thermoluminescence dosimetry (TLD). In this setup, the thermoluminescence (TL)-based point dose information is used to renormalize the PG. This new PG-TLD reference system is now extended to measurements in magnetic fields. Materials and Methods. Experiments were carried out on a conventional 6 MV linear accelerator (LINAC) and a 6 MV 0.35 T magnetic resonance (MR)-LINAC. Signal stability of TLD600 and TLD700 was examined without and with magnetic field. Afterwards, the combination of PAGAT PG and TL detectors was employed within a cylindrical phantom in presence of the magnetic field. Two scenarios were tested: (I) an air-filled phantom and (II) a water-filled phantom. For each scenario, two plans were irradiated: (a) opposed beams with a field size of 10 × 10 cm2 and (b) a 3D conformal plan assuring homogeneous target coverage using three equally distributed coplanar beams. Results. Mean relative uncertainty of TL calibration reproducibility for TLD600/TLD700 was 0.49%/0.85% at the MR-LINAC and 0.48%/0.83% for the conventional LINAC. Individual TL calibration coefficients of TLD600 and TLD700 behaved differently in the presence of the magnetic field. An average difference of (3.29 ± 0.89)% occurred for all TLD600, whereas the result for TLD700 is not quite as clear with (1.09 ± 0.89)% after excluding some outliers. Using the TL dose information for PG renormalization, high 3D gamma passing rates were achieved using the 3%/2 mm criteria: 91.0% (Ia), 92.6% (Ib), 94.3% (IIa), 97.4% (IIb). Conclusion. This study shows that TL signal reproducibility is not affected by a low magnetic field. Nevertheless, absolute calibration coefficients of the individual detectors indicate a dependency on the magnetic field. Hence, a calibration at the appropriate LINAC type is recommended. Furthermore, the previously established renormalization method for PG was applied to measurements at a MR-LINAC and was verified as suitable for evaluations of homogeneous dose distribution in the target volume.