Including Intensity Modulated Radiation Therapy Research Articles

2024 Guidelines for reporting radiation therapy in veterinary medicine.

Evidence-based medicine drives patient care decision-making; thus, accurate and complete reporting in scientific publications is paramount. A checklist for complete reporting of veterinary radiation therapy was proposed in 2012 using the recommendations of the International Commission of Radiation Units and Measurements (ICRU). The purpose of this study is to review the 2012 checklist and propose updates based on changes in technology. Significant technology advancements have gained traction in veterinary medicine, including intensity-modulated radiation therapy (IMRT) and stereotactic radiation therapy (SRT), both of which have related modality-specific ICRU reporting recommendations. The 2012 checklist and proposed 2024 checklist are then used to assess the completeness of reporting in veterinary radiation oncology publications between 2015 and 2022, of which one hundred and eight publications met the inclusion criteria. Prior to the publication of the 2012 checklist (2005-2010), only nine checklist items showed a good level of completeness in reporting, and from 2015 to 2022, this increased to 16 items. Encouraging and/or requiring the use of reporting checklists at the time of manuscript submission may be responsible for this improvement in reporting. Using the 2024 checklist, which is more relevant to publications discussing IMRT and SRT treatments, only 14 of the analyzed checklist items (34%) show a good level of completeness in reporting, suggesting there is a need for updated guidelines to capture the nuances of advanced techniques. This study proposes a 2024 checklist that can be used as a guideline for future reporting of radiation therapy in veterinary medicine.

Contemporary radiation therapy use in Hodgkin lymphoma

Radiation therapy assumes a pivotal role in Hodgkin lymphoma management, especially within combined modality therapy. It serves as a cornerstone in early-stage disease and in mitigating high-risk instances of local relapse in advanced stages. Over recent decades, radiation therapy has undergone significant advancements, notably alongside diagnostic imaging improvements, facilitating the reduction of radiation field size and dosage. This progress has notably led to minimized toxicity while upholding treatment efficacy.This comprehensive review extensively evaluates the indications and advancements in radiation therapy for Hodgkin lymphoma, with a primary focus on enhancing treatment efficacy while minimizing radiation-related toxicities. The exploration encompasses a detailed examination of various radiation fields, techniques and delivery modalities employed in Hodgkin lymphoma treatment, including intensity-modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT), and proton therapy. It delves into the intricacies of optimal dose selection and treatment planning strategies aimed at achieving maximal disease control while concurrently minimizing the risk of long-term side effects.

Innate Immune System in the Context of Radiation Therapy for Cancer.

Radiation therapy (RT) remains an integral component of modern oncology care, with most cancer patients receiving radiation as a part of their treatment plan. The main goal of ionizing RT is to control the local tumor burden by inducing DNA damage and apoptosis within the tumor cells. The advancement in RT, including intensity-modulated RT (IMRT), stereotactic body RT (SBRT), image-guided RT, and proton therapy, have increased the efficacy of RT, equipping clinicians with techniques to ensure precise and safe administration of radiation doses to tumor cells. In this review, we present the technological advancement in various types of RT methods and highlight their clinical utility and associated limitations. This review provides insights into how RT modulates innate immune signaling and the key players involved in modulating innate immune responses, which have not been well documented earlier. Apoptosis of cancer cells following RT triggers immune systems that contribute to the eradication of tumors through innate and adoptive immunity. The innate immune system consists of various cell types, including macrophages, dendritic cells, and natural killer cells, which serve as key mediators of innate immunity in response to RT. This review will concentrate on the significance of the innate myeloid and lymphoid lineages in anti-tumorigenic processes triggered by RT. Furthermore, we will explore essential strategies to enhance RT efficacy. This review can serve as a platform for researchers to comprehend the clinical application and limitations of various RT methods and provides insights into how RT modulates innate immune signaling.

Relationship between the Patients’ Setup Errors with Dosimetric and Radiobiologic Parameters in Whole Breast Radiotherapy

Purpose: This study aimed to investigate the effect of the patients’ setup errors on dosimetric and radiobiologic parameters for left-sided Whole-Breast Irradiation (WBI) in three different radiotherapy techniques, including Intensity-Modulated Radiation Therapy (IMRT), Field-In-Field (FIF), and Conventional Wedge (CW).
 Materials and Methods: Computed Tomography (CT) images of 10 female patients with early-stage left-sided breast cancer were used to simulate different radiotherapy techniques (IMRT, FIF, and CW). The dosimetric parameters; Conformity Index (CI), Homogeneity Index (HI), the dose received by at least 95% (D95%) of Planning Tumor Volume (PTV), the volume of lung and heart that respectively received at least 20% (V20%) and 40% (V40%) of the prescribed dose, as well as, the radiobiologic parameters, including Tumor Control Probability (TCP) and Normal Tissue Complication Probability (NTCP) were assessed for setup errors in patients. The setup errors were assessed by shifting the isocenters and gantry angles of the treatment plans.
 Results: The D95% of the PTV for an isocenter misplacement plan in the posterior direction decreased by 66.99 (IMRT), 71.86 (CW), and 68.25% (FIF). The TCP of the PTV was reduced by 26.66, 39.16, and 36.97% for IMRT, CW, and FIF techniques, respectively. Increasing gantry angle by a ±10 degree caused a 43%, 41%, and 41% decrease in the D95% of IMRT, FIF, and CW techniques, respectively. The TCP values decreased about 18% in all three techniques with a ±10 degree gantry angle shift; however, the NTCP values of the heart and lungs increased for all three methods. The CI and HI values had significantly more changes with increasing setup errors in the IMRT than in the two techniques.
 Conclusion: The radiobiologic parameters in IMRT were less sensitive to setup errors compared to FIF and CW techniques. The radiobiological parameters can help estimate the setup errors along with physical parameters during breast radiotherapy.

AAPM Task Group Report 307: Use of EPIDs for Patient-Specific IMRT and VMAT QA.

Electronic portal imaging devices (EPIDs) have been widely utilized for patient-specific quality assurance (PSQA) and their use for transit dosimetry applications is emerging. Yet there are no specific guidelines on the potential uses, limitations, and correct utilization of EPIDs for these purposes. The American Association of Physicists in Medicine (AAPM) Task Group 307 (TG-307) provides a comprehensive review of the physics, modeling, algorithms and clinical experience with EPID-based pre-treatment and transit dosimetry techniques. This review also includes the limitations and challenges in the clinical implementation of EPIDs, including recommendations for commissioning, calibration and validation, routine QA, tolerance levels for gamma analysis and risk-based analysis. Characteristics of the currently available EPID systems and EPID-based PSQA techniques are reviewed. The details of the physics, modeling, and algorithms for both pre-treatment and transit dosimetry methods are discussed, including clinical experience with different EPID dosimetry systems. Commissioning, calibration, and validation, tolerance levels and recommended tests, are reviewed, and analyzed. Risk-based analysis for EPID dosimetry is also addressed. Clinical experience, commissioning methods and tolerances for EPID-based PSQA system are described for pre-treatment and transit dosimetry applications. The sensitivity, specificity, and clinical results for EPID dosimetry techniques are presented as well as examples of patient-related and machine-related error detection by these dosimetry solutions. Limitations and challenges in clinical implementation of EPIDs for dosimetric purposes are discussed and acceptance and rejection criteria are outlined. Potential causes of and evaluations of pre-treatment and transit dosimetry failures are discussed. Guidelines and recommendations developed in this report are based on the extensive published data on EPID QA along with the clinical experience of the TG-307 members. TG-307 focused on the commercially available EPID-based dosimetric tools and provides guidance for medical physicists in the clinical implementation of EPID-based patient-specific pre-treatment and transit dosimetry QA solutions including intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) treatments.

Dosimetric Planning Comparison for Left-Sided Breast Cancer Radiotherapy: The Clinical Feasibility of Four-Dimensional-Computed Tomography-Based Treatment Planning Optimization.

Background: Adjuvant whole-breast radiotherapy (RT) is a significant part of the standard of care treatment after breast cancer (BC) conserving surgery. Modern techniques including intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) have constituted to better target coverage and critical organs sparing. However, BC survivors are at risk of developing radiation-induced cardiac toxicity. Hence, deep-inspiration breath-hold (DIBH) techniques have been implemented at many centers to further reduce cardiac exposure but require compliance. 4D-CT robust optimization can account for heart intrafractional motion per breathing phase. The optimization has been explored in cardiac sparing of breast IMRT compared to DIBH in a small sample size but has not been evaluated in substructures sparing, nor in VMAT. To provide patients who are not compliant to breath-hold with an optimal treatment approach, various heart sparing techniques need to be evaluated for statistical significance and clinical feasibility.Aim: This retrospective study aimed to provide an extensive dosimetric heart sparing comparison of free-breathing, 4D-CT-based treatment planning, including robust optimization with DIBH-based treatment planning. Combinations of forward and inverse IMRT and VMAT are also considered.Methods: Fifteen early stage left-sided BC standard treatment plans were selected. Breast, lung, left anterior descending artery (LAD), left ventricle (LV), and the whole heart were contoured on each 4D-CT phase and DIBH CT dataset. Each treatment plan was optimized using forward/inverse IMRT and VMAT on the following CT datasets: DIBH, average 4D-CT, and the complete 4D-CT dataset needed for robust optimization. Dose-volume histograms were used to compare V5GyHeart, mean heart dose, mean and max LAD dose, mean LV dose, and V50%Lung.Results: All RT techniques assessed including 4D robust optimization were clinically feasible. Statistically significant differences in mean heart, LAD and LV dose, max LAD dose, and V5GyHeart (p < 0.01) but no difference in V50%Lung (p = 0.29) were found between different techniques. IMRT DIBH achieved the optimal cardiac and substructure sparing among treatment plans. 4D robust IMRT had significantly greater mean heart and LV dose than DIBH IMRT (p ≤ 0.01), except LAD dose. Among free-breathing methods, no difference in all cardiac and substructure dose parameters was observed (p > 0.2) in comparing forward and inverse IMRT with average 4D-CT, inverse average 4D-CT, and 4D robust with IMRT, and between average 4D-CT VMAT and 4D robust VMAT. Only V5GyHeart and mean LV dose were significantly greater in 4D robust VMAT (p < 0.01) compared to DIBH VMAT. Mean heart and LV doses were significantly reduced (p < 0.01) in DIBH IMRT compared to DIBH VMAT. Moreover, mean heart and LV dose, V5GyHeart were significantly reduced in inverse IMRT average 4D-CT compared to average 4D-CT VMAT (p < 0.02) and in 4D robust IMRT compared to 4D robust VMAT (p < 0.04).Conclusion: This study demonstrated the clinical feasibility of 4D robust optimization in limiting the cardiac and substructures dose during free-breathing RT with both IMRT/VMAT for patients who are not compliant with breath-hold RT. However, this study also presents that 4D robust optimization can reduce LAD dose but not fully outperform DIBH or conventional 4D-CT-based planning with IMRT/VMAT in heart sparing in treating early staged left-sided BC patients.

Patterns of the use of advanced radiation therapy techniques for the management of bone metastases and the associated factors in Victoria.

IntroductionTo describe the pattern of the use of advanced radiation therapy (RT) techniques, including intensity‐modulated RT (IMRT), volumetric modulated arc therapy (VMAT), and stereotactic body RT (SBRT) for the management of bone metastases (BM), and the associated factors in Victoria.MethodsWe used a population‐based cohort of patients from the state‐wide Victorian Radiotherapy Minimum Data Set (VRMDS) who received RT for BM between 2012 and 2017. The primary outcome was proportion of RT courses using advanced RT techniques. The Cochran‐Armitage test for trend was used to evaluate temporal trend in advanced RT use. Multinomial logistic regression was used to identify factors associated with advanced RT use.ResultsA total of 18,158 courses of RT were delivered to 10,956 patients–16,626 (91.6%) courses were 3D conformal RT, 857 (4.7%) IMRT/VMAT and 675 (3.7%) SBRT. There was a sharp increase in IMRT/VMAT use from <1% in 2012–2015, to 10.1% in 2016 and 16.3% in 2017 (P‐trend < 0.001). Increase in SBRT use was more gradual, from 1.2% in 2012 to 4.8% in 2016 and 5.5% in 2017 for SBRT (P‐trend<0.001). In multivariate analyses, year of RT was the strongest predictor of IMRT/VMAT use (OR = 41; 95%CI = 25–67; P < 0.001, comparing 2012–2013 and 2016–2017). Primary tumour type (prostate cancer) was the strongest predictor of SBRT use (OR = 6.07; 95% CI = 4.19–8.80; P < 0.001).ConclusionOverall, there was increasing trend in the use of advanced RT techniques for BM in Victoria, with a distinct pattern for IMRT/VMAT compared with SBRT – SBRT uptake was more gradual while IMRT/VMAT uptake was abrupt, occurring contemporaneously with Medicare Benefit Scheme funding changes in 2016.

Geriatric oncology: principles and perspectives

The incidence and prevalence of cancer in the older age person are increasing with the aging of the population. The management of cancer in the older patient is, to some extent, a moving target, affected by the new understanding of cancer and aging and by scientific and technological ad­vances. The prevention and treatment of cancer in the elderly should be funded on physiologic rather than chro­no­lo­gic age, that is on residual life expectancy and resilience. The Comprehensive Geriatric Assessment represents at pre­sent the only instrument validated for the assessment of phy­­sio­­lo­gic age. New forms of cancer treatment, including intensity modulated radiation therapy, stereotactic ra­dio­­sur­­ge­ry, targeted agents and immune checkpoint in­­hi­­bi­­tors, have made cancer treatment better tolerated by the elderly. Among the antidotes to chemotherapy toxicity, the “pan-protector” trilaciclib and ALRN 6924 appear most pro­­mi­sing.

Initial clinical experience treating patients with palliative radiotherapy for malignant pleural mesothelioma on the HalcyonTM linear accelerator.

Radiation therapy (RT) can provide effective symptomatic palliation in patients with malignant pleural mesothelioma (MPM). Advances in RT technology, including intensity-modulated RT (IMRT) and volumetric-modulated arc therapy (VMAT), have improved treatment conformality, potentially improving the therapeutic ratio of RT. A novel 6-MV flattening-filter-free O-ring linear accelerator, HalcyonTM (Varian Medical Systems, Palo Alto, CA, USA), was built to provide such advanced therapies, while possibly reducing treatment time. Here, we report the initial clinical experience using HalcyonTM to deliver palliative RT for patients with MPM. We retrospectively assessed consecutive patients with MPM who received thoracic RT on HalcyonTM. Their electronic medical records were reviewed for clinical, RT planning, treatment timing, and image-guidance RT (IGRT) data. Four patients with metastatic MPM received palliative RT on HalcyonTM between 1/2017-1/2020 for severe pain (50%), dysphagia (25%), or dyspnea (25%). Targets included a combination of pleura, chest wall, lung, hilum, and mediastinum, with patient-specific dose and fractionation regimens ranging from 20-45 Gy in 5-15 fractions, and 75% of patients receiving concurrent systemic therapy. Pre-specified target and organ-at-risk constraints were met for nearly all plans. At a median follow-up of 2.2 months (range, 1.6-7.1 months), all patients experienced either improved (75%) or stable (25%) tumor-related symptoms following palliative RT. The mean 3D vector couch correction was 0.67±0.15 cm. The mean beam-on, treatment (beam-on plus cone-beam computed tomography times), and approximated total room usage times were 1.6±0.2, 1.8±0.2, and 9.8±0.2 min, respectively. Grade 2 fatigue and cough occurred in 25% and 25% of patients, and no patients experienced Grade ≥3 toxicity. In this initial clinical experience treating patients with palliative RT for MPM on HalcyonTM, treatment provided symptom palliation and local control across multiple palliative scenarios, with minimal toxicity, acceptable dosimetry, and setup corrections and treatment times that compared favorably with other published experiences of MPM RT. Palliative RT on HalcyonTM can provide patients with MPM quick and safe tumor-related symptom relief, even in a frail, elderly population.

Migration of treatment planning system using existing commissioned planning system

AbstractIntroduction:Commissioning of a new planning system involves extensive data acquisition which can be onerous involving significant clinic downtime. This could be circumvented by extracting data from existing treatment planning system (TPS) to speed up the process.Material and methods:In this study, commissioning beam data was obtained from a clinically commissioned TPS (Pinnacle™) using Matlab™ generated Pinnacle™ executable scripts to commission an independent 3D dose verification TPS (Eclipse™). Profiles and output factors for commissioning as required by Eclipse™ were computed on a 50 × 50 × 50 cm3 water phantom at a dose grid resolution of 2 mm3. Verification doses were computed and compared to clinical TPS dose profiles based on TG-106 guidelines. Standard patient plans from Pinnacle™ including intensity modulated radiation therapy and volumetric modulated arc therapy were re-computed on Eclipse™ TPS while maintaining the same monitor units. Computed dose was exported back to Pinnacle for comparison with the original plans. This methodology enabled us to alleviate all ambiguities that arise in such studies.Results:Profile analysis using in-house software showed that for all field sizes including small multi-leaf collimator-generated fields, &gt;95% of infield and penumbra data points of Eclipse™ match Pinnacle™ generated and measured profiles with 2%/2 mm gamma criteria. Excellent agreement was observed in the penumbra regions, with &gt;95% of the data points passing distance to agreement criteria for complex C-shaped and S-shaped profiles. Dose volume histograms and isodose lines of patient plans agreed well to within a 0·5% for target coverage.Findings:Migration of TPS is possible without compromising accuracy or enduring the cumbersome measurement of commissioning data. Economising time for commissioning such a verification system or for migration of TPS can add great QA value and minimise downtime.

Rethinking the Role of Radiation Therapy in the Management of Epithelial Ovarian Cancer.

Radiation has been relegated to a palliative role in the management of epithelial ovarian cancer (EOC). Contemporary radiation techniques, including intensity modulated radiation therapy (IMRT), stereotactic body radiation therapy (SBRT), and image-guided radiation therapy, enable conformal treatment that controls local disease with minimal morbidity. Recent studies from multiple institutions support the role of radiation in the ablative treatment of oligometastatic disease and control of locally recurrent and metastatic disease. Effective local treatment with radiation complements the role of systemic therapy in the management of EOC; reduces symptoms and disease burden, and may contribute to a prolonged drug free interval.

The relationship between ventricular volume and whole‐brain irradiation dose in central nervous system germ cell tumors

Advanced irradiation techniques, including intensity-modulated radiation therapy (IMRT), aim to limit irradiation to adjoining tissues by conforming beams to a well-defined volume. In intracranial germinomas, whole-ventricular IMRT decreases the volume of irradiation to surrounding parenchyma. This study examined the relationship between ventricular volume and radiation dose to surrounding tissue. We retrospectively reviewed age, sex, ventricular and brain volume, ventricular dose, and volume of brain that received 12Gy (V12) for patients diagnosed with germ cell tumors at our institution treated with whole-ventricular IMRT between 2002 and 2016. Variables were assessed for correlation and statistical significance. Forty-seven patients were analyzed. The median whole-ventricular irradiation dose was 24Gy with a median boost dose of 30Gy. The median ventricular volume was 234.3 cm3 , and median brain volume was 1408 cm3 . There was no significant difference between mean ventricular volume of suprasellar versus pineal tumors (P=.95). The median V12 of the brain, including the ventricles, was 58.9%. The strongest correlation was between ventricular volume and V12, with an r2 (coefficient of determination) of .47 (P<.001). Multiple regression analysis indicated that total boost dose and boost planning target volume significantly predicted V12 (P<.001). Although whole-ventricular IMRT limited irradiation to surrounding tissue in our cohort, a significant percentage of the brain received at least 12Gy. This study suggests that there is a positive correlation between ventricular volume and the volume of brain parenchyma receiving at least 12Gy with an important contribution from the boost phase of treatment.

Evaluating small field dosimetry with the Acuros XB (AXB) and analytical anisotropic algorithm (AAA) dose calculation algorithms in the eclipse treatment planning system

AbstractBackground:An increasing number of external beam treatment modalities including intensity modulated radiation therapy, volumetric modulated arc therapy (VMAT) and stereotactic radiosurgery uses very small fields for treatment planning and delivery. However, there are major challenges in small photon field dosimetry, due to the partial occlusion of the direct photon beam source’s view from the measurement point, lack of lateral charged particle equilibrium, steep dose-rate gradient and volume averaging effect of the detector response and variation of the energy fluence in the lateral direction of the beam. Therefore, experimental measurements of dosimetric parameters such as percent depth doses (PDDs), beam profiles and relative output factors (ROFs) for small fields continue to be a challenge.Materials and Methods:In this study, we used a homogeneous water phantom and the heterogeneous anthropomorphic stereotactic end-to-end verification (STEEV) head phantom for all dose measurements and calculations. PDDs, lateral dose profiles and ROFs were calculated in the Eclipse Treatment Planning System version 13·6 using the Acuros XB (AXB) and the analytical anisotropic algorithms (AAAs) in a homogenous water phantom. Monte Carlo (MC) simulations and measurements using the Exradin W1 Scintillator were also accomplished for four photon energies: 6 MV, 6FFF, 10 MV and 10FFF. Two VMAT treatment plans were generated for two different targets: one located in the brain and the other in the neck (close to the trachea) in the head phantom (CIRS, Norfolk, VA, USA). A Varian Truebeam linear accelerator (Varian, Palo Alto, CA, USA) was used for all treatment deliveries. Calculated results with AXB and AAA were compared with MC simulations and measurements.Results:The average difference of PDDs between W1 Exradin Scintillator measurements and MC simulations, AAA and AXB algorithm calculations were 1·2, 2·4 and 3·2%, respectively, for all field sizes and energies. AXB and AAA showed differences in ROF of about 0·3 and 2·9%, respectively, compared with W1 Exradin Scintillator measured values. For the target located in the brain in the head phantom, the average dose difference between W1 Exradin Scintillator and the MC simulations, AAA and AXB were 0·2, 3·2 and 2·7%, respectively, for all field sizes. Similarly, for the target located in the neck, the respective dose differences were 3·8, 5·7 and 3·5%.Conclusion:In this study, we compared dosimetric parameters such as PDD, beam profile and ROFs in water phantom and isocenter point dose measurements in an anthropomorphic head phantom representing a patient. We observed that measurements using the W1 Exradin scintillator agreed well with MC simulations and can be used efficiently for dosimetric parameters such as PDDs and dose profiles and patient-specific quality assurance measurements for small fields. In both homogenous and heterogeneous media, the AXB algorithm dose prediction agrees well with MC and measurements and was found to be superior to the AAA algorithm.

Recent advances in gynecologic radiation oncology.

Radiation has long been a primary treatment modality in locally advanced gynecologic carcinomas and a tool for palliation of metastatic disease. Here we review advances in imaging and radiation technologies and the corresponding clinical evolution of the role for radiation oncology in the treatment of gynecologic malignancies. Advances in MRI are impacting diagnosis, radiation target delineation, planning, treatment delivery, and response assessment. The combination of MRI and PET-computed tomography (PET-CT) has the potential to significantly change treatment recommendations as compared with a single imaging modality. Advances in radiation delivery including intensity modulated radiation therapy (IMRT) and stereotactic ablative radiotherapy (SABR) have expanded the role for radiation in the definitive treatment of high risk and oligometastatic ovarian cancer. Finally, global disparities in oncology resources has led to the development of resource stratified treatment guidelines for gynecologic malignancies. The use of ultrasound for brachytherapy planning may help improve access to this critical treatment modality. As imaging and radiation technologies advance, the indications for radiation in the treatment of gynecologic malignancies continues to evolve. Here we review the changing landscape of radiation oncology in the multidisciplinary management of gynecologic cancers.

Clinical Implementation of an In vivo Dose Verification System Based on a Transit Dose Calculation Tool for 3D-CRT

We developed and evaluated an algorithm to calculate the target radiation dose in cancer patients by measuring the transmitted dose during 3D conformal radiation treatment (3D-CRT) treatment. The patient target doses were calculated from the transit dose, which was measured using a glass dosimeter positioned 150 cm from the source. The accuracy of the transit dose algorithm was evaluated using a solid water phantom for five patient treatment plans. We performed transit dose-based patient dose verification during the actual treatment of 34 patients who underwent 3D-CRT. These included 17 patients with breast cancer, 11 with pelvic cancer, and 6 with other cancers. In the solid water phantom study, the difference between the transit dosimetry algorithm with the treatment planning system (TPS) and the measurement was −0.10 ± 1.93%. In the clinical study, this difference was 0.94 ± 4.13% for the patients with 17 breast cancers, −0.11 ± 3.50% for the eight with rectal cancer, 0.51 ± 5.10% for the four with bone cancer, and 0.91 ± 3.69% for the other five. These results suggest that transit-dosimetry-based in-room patient dose verification is a useful application for 3D-CRT. We expect that this technique will be widely applicable for patient safety in the treatment room through improvements in the transit dosimetry algorithm for complicated treatment techniques (including intensity modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT)).

Advances in the use of motion management and image guidance in radiation therapy treatment for lung cancer.

The development of advanced radiation technologies, including intensity-modulated radiation therapy (IMRT), stereotactic body radiation therapy (SBRT) and proton therapy, has resulted in increasingly conformal radiation treatments. Recent evidence for the importance of minimizing dose to normal critical structures including the heart and lungs has led to incorporation of these advanced treatment modalities into radiation therapy (RT) for non-small cell lung cancer (NSCLC). While such technologies have allowed for improved dose delivery, implementation requires improved target accuracy with treatments, placing increasing importance on evaluating tumor motion at the time of planning and verifying tumor position at the time of treatment. In this review article, we describe issues and updates related both to motion management and image guidance in the treatment of NSCLC.

(P21) Health Disparities and Inequities in Radiation Therapy for Prostate Cancer

Well-documented health disparities exist in prostate cancer (PCa) incidence, healthcare resource utilization, and mortality. However, inequities in PCa radiation therapy (RT) specifically have not yet been comprehensively summarized. To review and summarize the reported health disparities and inequities in healthcare resource utilization for PCa undergoing RT. A comprehensive literature search in the PubMed database was generated with the query “prostate AND (radiation OR radiotherapy OR proton) AND (disparities OR “socioeconomic status” OR “health services research” OR inequity OR race[Title])”. Studies were included if they examined RT or related resource utilization and addressed health inequities in the United States. The initial query returned 281 studies with 79 meeting inclusion criteria. These consisted of 67 population-based analyses, 5 single-institution analyses, 3 prospective studies, 3 survey-based studies, and 1 multi-institutional review. Of the population-based analyses, 13 studies used the National Cancer Database (NCDB) and 37 studies used Surveillance, Epidemiology, and End Results (SEER) databases; the remainder used state specific registries and Medicare and Veterans Affairs databases. Studies were published between 1991 and 2017, with 62 of 79 (78%) published after 2010. The most common health inequities reported pertained to age (23 studies), race and ethnicity (60), socioeconomic status (22), insurance status (18), and hospital or practice characteristics (24). These variables resulted in inequities in: screening and staging methods (3 studies) and management approach and treatment intent (44), e.g. definitive versus non-definitive management. Inequities in radiation modality type, including intensity-modulated RT (IMRT), proton therapy, brachytherapy, and stereotactic body RT (SBRT) were assessed in 43 studies. Increased age was generally associated with a decreased likelihood of receiving definitive treatment. For instance, one SEER study of 86,544 patients diagnosed with localized PCa between 2006-2011 demonstrated that patients age 80-89 received curative treatment less frequently than those age 66-79, even with adjustment for comorbidity and performance status (OR 0.18). Non-white race was generally associated with decreased healthcare resource utilization in multiple aspects. For example, for initial staging, black patients with low risk PCa were less likely to undergo multiparametric MRI in one single-institution analysis of 705 patients from 2005-2013 (OR 0.51). Black patients were less likely to receive definitive therapy, even after adjustment for income, education, and insurance status. Among RT modalities, black patients received proton therapy and brachytherapy less frequently than white patients. Additionally, the time from diagnosis to definitive treatment was longer for black patients, especially in high risk disease. Similar inequities were also observed in Hispanic, Asian, and Pacific Islander patients. Lower socioeconomic status and insurance status (i.e. Medicaid/no insurance versus Medicare/private plans) were independently associated with decreased likelihood of receiving definitive therapy and increased likelihood of receiving RT versus prostatectomy. With regards to practice setting, academic cancer centers notably exhibited similar health inequities to community cancer centers. Significant inequities in the utilization of RT for PCa exist, with the most published RT outcomes pertaining to age, race, socioeconomic status, insurance status, and practice setting. These inequities likely contribute to disparities in overall PCa morbidity and mortality.

Two-and-a-half-year clinical experience with the world's first magnetic resonance image guided radiation therapy system

PurposeMagnetic resonance image guided radiation therapy (MR-IGRT) has been used at our institution since 2014. We report on more than 2 years of clinical experience in treating patients with the world's first MR-IGRT system. Methods and materialsA clinical service was opened for MR-IGRT in January 2014 with an MR-IGRT system consisting of a split 0.35T magnetic resonance scanner that straddles a ring gantry with 3 multileaf collimator-equipped 60Co heads. The service was expanded to include online adaptive radiation therapy (ART) MR-IGRT and cine gating after 6 and 9 months, respectively. Patients selected for MR-IGRT were enrolled in a prospective registry between January 2014 and June 2016. Patients were treated with a variety of radiation therapy techniques including intensity modulated radiation therapy and stereotactic body radiation therapy (SBRT). When applicable, online ART was performed and gating on sagittal 2-dimensional cine MR was used. The charts of patients treated with MR-IGRT were reviewed to report on the clinical and treatment characteristics of the initial patients who were treated with this novel technique. ResultsA total of 316 patients have been treated with the MR-IGRT system, which has been integrated into a high-volume clinic. The cases were most commonly selected for improved soft tissue visualization, ART, and cine gating. Seventy-six patients were treated with 3-dimensional conformal radiation therapy, 146 patients with intensity modulated radiation therapy, and 94 patients with SBRT. The most commonly treated disease sites were the abdomen (28%), breast (26%), pelvis (22%), thorax (19%), and head and neck (5%). Sixty-seven patients were treated with online ART over a total of 244 adapted fractions. Cine treatment gating was used for a total of 81 patients. ConclusionsMR-IGRT has been successfully implemented in a high-volume radiation clinic and provides unique advantages in the treatment of a variety of malignancies. Additional clinical trials are in development to formally evaluate MR-IGRT in the treatment of multiple disease sites with techniques such as SBRT and ART.

Efficacy and toxicity of rectal cancer reirradiation using IMRT for patients who have received prior pelvic radiation therapy

PurposeLocally recurrent rectal cancer may cause significant morbidity. Prior reports of rectal cancer reirradiation following local recurrence suggest treatment efficacy, with variable rates of late toxicity. Modern techniques including intensity modulated radiation therapy (IMRT) may improve the therapeutic index. We report outcomes for pelvic reirradiation as treatment for rectal cancer using IMRT. Methods and materialsThe records of 31 patients undergoing reirradiation for rectal cancer between 2004 and 2013 were reviewed. All patients underwent IMRT using an accelerated hyperfractionation (39 Gy in 1.5-Gy fractions delivered twice daily, n=15) or once-daily fractionation technique (median dose, 30.4 Gy; range, 27-40 Gy in 15-22 fractions; n = 16). The median cumulative dose was 77 Gy (range, 59-113), and the median interval from prior pelvic radiation therapy was 39.8 months (range, 10.1-307.6). Treatment intent was palliative in 20 patients and neoadjuvant or adjuvant in 11 patients. Surgery was generally reserved for patients with an isolated local recurrence. Concurrent chemotherapy was administered for 25/31 patients, most frequently capecitabine (n=11) or continuous infusion 5-fluorouracil (n=10). ResultsMedian follow-up was 11.3 months. The prescribed treatment was completed in 29/31 patients (93.5%). Among 18 patients with symptoms attributable to recurrent disease, successful palliation was achieved in 10/18 (55.6%). The rate of grade 2 and grade 3 acute toxicities was 32.3% and 3.2%, respectively. Local control rates at 1 and 2 years were 61.3% and 47.3%, respectively. Median overall survival was 21.9 months, and 1-year survival was 66.7% for patients who had surgical resection versus 58.7% for those who did not (P = .0802). ConclusionsRectal cancer reirradiation using IMRT is well-tolerated in the setting of prior pelvic radiation therapy. Given significant risk of local progression, further dose escalation may be warranted for patients with life expectancy exceeding 1 year.

Radiation dose effect in locally advanced non-small cell lung cancer.

Radiation is the foundation of treatment for locally advanced non-small cell lung cancer (NSCLC), and as such, optimal radiation dose is essential for successful treatment. This article will briefly review biological considerations of radiation dose and their effect in the context of three-dimensional conformal radiation therapy (3D-CRT) including intensity modulated radiation therapy (IMRT) and stereotactic body radiation therapy (SBRT) for NSCLC. It will focus on literature review and discussions regarding radiation dose effect in locally advanced NSCLC including potential severe and lethal toxicities of high dose radiation given with concurrent chemotherapy. Potential new approaches for delivering safe and effective doses by individualizing treatment based on functional imaging are being applied in studies such as the PET boost trial and RTOG1106. The RTOG concept of delivering high dose radiation to the more resistant tumors with the use of isotoxic dose prescription and adaptive planning will also be discussed in detail.