Radiation Treatment Techniques Research Articles

Review on high spatial resolution dosimetry with pixelated semiconductor detectors for radiation therapy

Current and emerging radiation therapy treatment techniques are characterized by complex and spatially non-uniform dose distributions with steep dose gradients delivered through high-precision dose placement with small radiation fields. Such approaches necessitate advanced verification tools. For accurate dose profile representation in stereotactic radiation therapy using megavoltage X-rays, the Nyquist theorem places the minimum sampling step as 2.5 mm that determines the required spatial resolution of the detectors for dose verification. For techniques such as micro- and mini-beam radiotherapy, micron-scale sampling is required, and sub-millimeter for particle therapy. Silicon semiconductor detectors provide the possibility of producing small sensitive volumes (including in arrays) without compromising mechanical robustness or sensitivity, therefore allowing for high spatial resolution dosimetry. They exhibit many properties of an ideal detector, while the properties of silicon detectors known to negatively influence response can be compensated for and minimized. As such, this work reviews the current status of semiconductor radiation detectors providing dose sampling by diodes with submillimeter sensitive volumes and a pitch of 2.5 mm or smaller for relative dosimetry in X-ray and electron external beam radiation therapy, brachytherapy, microbeam radiation therapy, proton, and heavy ion therapy. The following types of devices are discussed in this work, including commercial systems and those under development: one-dimensional and two-dimensional pixelated arrays (monolithic and single diode based).

Unveiling the Silent Threat: Radiation-Induced Coronary Artery Disease Among Young Patients – A Medical Physics Perspective Review

This comprehensive review presents the objectives and research framework for investigating radiation-induced coronary artery disease (RICAD) among young patients from a medical physics perspective. RICAD poses a silent threat to this population, necessitating a comprehensive understanding of its incidence, risk factors, long-term outcomes, mitigation strategies, underlying mechanisms, and predictive models. The study aims to investigate the incidence and prevalence of RICAD among young patients who have undergone radiation therapy for various medical conditions. The research involving RICAD amongst young patients has benefited greatly from the guidance and molding provided by the literature review, which has advanced our understanding of medical physics. By analyzing existing data and conducting longitudinal studies, the research intends to provide insights into the frequency of RICAD occurrence within this specific demographic. Identifying the risk factors associated with RICAD development in young patients is crucial for effective prevention and management. The research will explore factors such as radiation dose, treatment techniques, and patient-specific characteristics to determine their influence on RICAD incidence. This analysis will facilitate the development of targeted interventions and risk stratification strategies This study emphasizes how crucial it is to look into RICAD in pediatric patients concerning a medical physics standpoint. We can endeavor to improve the top leadership and outcomes for those who are most susceptible by comprehending the incidence, factors associated with risk, long-term consequences, mitigation measures, underlying mechanisms, and models for prediction linked with RICAD.

Treatment Related Acute Toxicities Between Treatment with 3D-CRT and IMRT in Localised Prostate Cancer.

To compare the acute toxicities of two radiation treatment techniques, intensity modulated radiation therapy (IMRT), and 3-dimensional conformal radiation therapy (3D-CRT) in localised prostate adenocarcinoma. Descriptive study. Place and Duration of the Study:Department of Oncology, Dr. Ziauddin Hospital, Karachi, Pakistan, from July 2016 to June 2022. Patients with localised prostate adenocarcinoma who underwent treatment using two different advanced radiotherapy techniques i.e., IMRT and 3D-CRT were recruited during the study period. They were followed up for six months for acute gastrointestinal (GI) and genitourinary (GU) adverse events (acute toxicities) related to both treatment modalities according to Modified radiation therapy oncology group (RTOG) criteria. The acute toxicities were assessed at the 2nd, 4th, and 6th week during treatment and at the 3rd and 6th month after treatment. There were 78 patients, with 39 patients in each group. The mean age was 68 ± 10 years in the 3D-CRT and 68 ± 07 years in the IMRT group. Patients in the IMRT group exhibited markedly lower treatment-related acute GI and GU effects at the end of 4th and 6th weeks for anorectal pain (p = 0.04) and (p = 0.01) and burning micturition (p = 0.003) and (p = 0.01), respectively. Furthermore, at 3 months anorectal pain (p = 0.02), loose stools (p = 0.005), and burning micturition (p = 0.01) were present and at 6 months anorectal pain was (p = 0.01) still present. Radiation therapy modalities 3D-CRT and IMRT both showed acceptable toxicity profile in the management of localised prostate cancer, while IMRT group exhibited significantly lower treatment-related acute GI and GU effects. 3D-CRT (3-Dimensional Conformal Radiation Therapy), IMRT (Intensity-Modulated Radiation Therapy), Radiation toxicity.

Dosimetric Comparison Between Proton and Photon Radiation Therapies for Pediatric Neuroblastoma

PurposeThe aim of this study is to determine the most beneficial radiation treatment technique for pediatric patients with thoracic and abdominal neuroblastoma (NBL), through a dosimetric comparison between photon Volumetric Modulated Arc Therapy and proton Intensity-Modulated Proton Therapy treatment plans. Materials and MethodsA retrospective analysis was conducted on a multicentre case series of 19 patients with thoracic and/or abdominal NBL who underwent radiation therapy, following the recommendations of the European protocol for high-risk NBL (HR-NBL2/SIOPEN). The prescribed dose was 21.6 Gy in 12 fractions (1.8 Gy/fraction) delivered over the preoperative disease volume. The dose volume histograms were analyzed for each patient, and a Wilcoxon signed-rank test with a significance level of 0.01 was employed to assess statistical differences between the dosimetric parameters investigated. Two homogeneity indices (HI and newHI) were compared to evaluate the uniformity in dose, delivered to the adjacent vertebrae (VBs_Adj). ResultsBoth radiation techniques conform to the protocol regarding CTV/PTV coverage for every location. Proton therapy resulted in statistically significant dose sparing for the heart and lungs in supradiaphragmatic locations and for the contralateral kidney, liver, spleen, and bowel in subdiaphragmatic locations. For both techniques, sparing the non-adjacent vertebrae (VBs_NAdj) results more challenging, although promising results were obtained. Furthermore, the dose delivered to the VBs_Adj was not statistically different, in terms of homogeneity, for the 2 radiation techniques that both met the protocol’s requirements. ConclusionThis dosimetric analysis highlights the potential of protons to reduce radiation dose to healthy tissue. These findings apply to all the investigated patients, regardless of primary tumor location, making proton therapy a valuable option for the treatment of neuroblastoma. However, a multidisciplinary assessment of each case is essential to ensure the selection of the most effective and suitable treatment modality.

Radiation Therapy With or Without Cisplatin for Local Recurrences of Endometrial Cancer: Results From an NRG Oncology/GOG Prospective Randomized Multicenter Clinical Trial.

Pelvic recurrence is a frequent pattern of relapse for women with endometrial cancer. A randomized trial compared progression-free survival (PFS) after treatment with radiation therapy alone as compared with concurrent chemotherapy. Between February 2008 and August 2020, 165 patients were randomly assigned 1:1 to receive either radiation treatment alone or a combination of chemotherapy and radiation treatment. The primary objective of this study was to determine whether chemoradiation therapy was more effective than radiation therapy alone at improving PFS. The majority of patients had low-grade (1 or 2) endometrioid histology (82%) and recurrences confined to the vagina (86%). External beam with either the three-dimensional or intensity modulated radiation treatment technique was followed by a boost delivered with brachytherapy or external beam. Patients randomly assigned to receive chemotherapy were treated with once weekly cisplatin (40 mg/m2). Rates of acute toxicity were higher in patients treated with chemoradiation as compared with radiation treatment alone. Median PFS was longer for patients treated with radiation therapy alone as compared with chemotherapy and radiation (median PFS was not reached for RT v 73 months for chemoradiation, hazard ratio of 1.25 (95% CI, 0.75 to 2.07). At 3 years, 73% of patients treated definitively with radiation and 62% of patients treated with chemoradiation were alive and free of disease progression. Excellent outcomes can be achieved for women with localized recurrences of endometrial cancer when treated with radiation therapy. The addition of chemotherapy does not improve PFS for patients treated with definitive radiation therapy for recurrent endometrial cancer and increases acute toxicity. Patients with low-grade and vaginal recurrences who constituted the majority of those enrolled are best treated with radiation therapy alone.

Study of PRESAGE® dosimeter for end-to-end 3D radiotherapy verification using an anthropomorphic phantom with bespoke dosimeter insert.

Modern radiotherapy techniques have advanced and become more sophisticated. End-to-end 3D verification of the complex radiotherapy dose distribution in an anthropomorphic phantom can ensure the accuracy of the treatment delivery. The phantoms commonly used for dosimetry are homogeneous solid water phantom which lacks the capability to measure the 3D dose distribution for heterogeneous tissues necessary for advanced radiotherapy techniques. Therefore, we developed an end-to-end 3D radiotherapy dose verification system based on MAX-HD anthropomorphic phantom (Integrated Medical Technologies Inc., Troy, New York) with bespoke intracranial insert for PRESAGE® dosimeter. In this study, several advanced radiotherapy treatment techniques of various levels of complexity; 3D-CRT, IMRT and VMAT treatment, were planned for a 20mm diameter of a spherical target in the brain region and delivered to the phantom. The dosimeters were read out using an in-house developed optical computed tomography (OCT) imaging system known as 3DmicroHD-OCT. It was found that the measured dose distribution of the PRESAGE® when compared with the measured dose distribution of EBT film and Monaco TPS has a maximum difference of less than 3% for 3D-CRT, IMRT and VMAT treatment plans. The gamma analysis results of PRESAGE® in comparison to EBT film and Monaco TPS show pass rates of more than 95% for the criteria of 3% dose difference and 3mm distance-to-agreement. This study proves the capability of PRESAGE® and bespoke MAX-HD phantom in conjunction with the 3DmicroHD-OCT system to measure 3D dose distribution for end-to-end dosimetry verification.

Dosimetric Comparison of The Effects of Different Treatment Plan Techniques on Reduction in Critical Organs in Whole Brain Radiotherapy Application

Different radiotherapy treatment techniques can be used in whole-brain radiotherapy (WBRT). This study aims to investigate the dosimetric advantages of the anterior isocenteric (AI) technique which is produced as an alternative to the central isocentric (CI) technique. 25 whole brain patients were included in this retrospective study. Plans were made with two treatment techniques for each patient. One central isocenter (CI) was made using a conventional helmet field (HF) to center the whole brain, which is the isocenter of the target volume. An automatic margin of 5 mm was given to the planning target volume (PTV) with multileaf collimators (MLC) for both plans. For CI and AI techniques, a total dose of 30 Gy was given in 10 fractions with 6 MV photon energy. The two planning techniques were compared dosimetrically. The dose homogeneity index (DHI) had lower values in the AI plan according to CI plans significantly (p=0.049). There was a 6,57% difference between CI and AI planning techniques for the maximum dose of the right lens. For the minimum dose and mean dose AI plans significantly had lower values according to the CI plan (p=0.001 and p=0.028 respectively). In this dosimetric study, we found that the AI treatment technique for WBRT was superior to the CI technique for DHI and organs at risk. We recommended to use the AI technique, especially to better protect organs at risk in WBRT.

The Outcome of Anaplastic Glioma Treated at a Tertiary Cancer Care Institute in South Asia

Objective: Anaplastic glioma is a highly aggressive brain tumor that often occurs in young adults. There is a lack of data from India on anaplastic gliomas. This study aims to evaluate the prognostic factors of anaplastic glioma and correlate them with the outcome. Materials and Methods: This is a retrospective observational study of 57 patients with anaplastic glioma treated from 1996 to 2015 in a cancer institute in Chennai. We captured data from the cancer institute’s hospital-based electronic health record tumor registry and correlated factors including age, sex, histology, site of disease, type of surgery, adjuvant treatment, and radiation treatment technique with outcome. For the calculation of progression-free survival (PFS) and Overall Survival (OS), we used Statistical Package for Social Science (SPSS) software. Result: This analysis included fifty-seven patients, with a median follow-up of 34 months. The median progression-free survival (PFS) and overall survival (OS) were 28 and 41 months, respectively. On univariate analysis, factors associated with improved survival include Anaplastic Oligodendroglioma histology (HR-0.43, CI-0.22-0.80, P=0.006), Frontal lobe location (HR-1.96, CI-1.07-3.58, P=0.025) Gross total resection (HR-1.94, CI-1.03-3.64, P=0.034), and addition of Temozolamide (HR-2.09, CI-1.14-3.84, P=0.014). On multivariate analysis Anaplastic Oligodendroglioma histology, (HR-0.49,CI-0.25-0.95,P=0.037), Frontal lobe (HR-2.14,CI-1.12-4.07,P=0.021), Gross total resection (HR-2.89,CI-1.47-5.69,P=0.002) and addition of Temozolamide (HR-2.02,CI-1.07-3.81,P=0.029) remained significant factors for improved OS. Conclusion: Among the various clinical and treatment-related prognostic factors, our study revealed that anaplastic oligodendroglioma histology, frontal lobe location, gross total resection, and addition of temozolomide chemotherapy to radiation showed improved outcomes.

Stereotactic radiotherapy: An educational narrative review

AbstractStereotactic radiotherapy is a term collectively used to describe the radiation treatment techniques that allow for the delivery of highly precise ionizing radiation. It is usually a high dose per session in single or few fractions. This treatment approach has been in medical use for over six decades and has primarily evolved in the last two decades. Many patients benefit from this unique non‐conventional radiotherapy approach. Its indications include various malignant, benign and functional problems in cranial and body sites. This technique is not widespread in developing countries compared to developed countries. This work is an educational narrative review for learners in radiation oncology. We aim to share the knowledge of this practice to improve precision radiation oncology globally. This review summarizes the basics of stereotactic radiotherapy, the technical prerequisites, the clinical considerations, the practical recommendations and the learning points from each site‐specific region.

Incorporating Immunotherapy with Radiotherapy for Lymphomas

Radiotherapy and/or chemotherapy have been used for nearly 100 years to treat lymphoma. Recently, immunotherapy has been incorporated into the treatment of lymphomas. Here, we will review both the role of immunotherapy in lymphoma as well as the feasibility of incorporating immunotherapies with conventional lymphoma treatments, especially radiotherapy. Immunotherapy agents include checkpoint inhibitors that target the PD-1/PD-L1 axis, CTLA-4, or CD47. In addition, other immunotherapy agents such as bi-specific antibodies and CD19 CAR-T cell therapy are being implemented in various non-Hodgkin’s lymphomas. Extrapolating from observations in other disease sites and incorporating immunotherapy with conventional treatments of lymphoma, including radiotherapy, may have opposing effects. Radiotherapy may stimulate anti-tumor immune responses that synergize with immunotherapies. In contrast, radiotherapy, as well as chemotherapy, may also induce local and systemic immune dysfunction which reduces the efficacy of immunotherapies. With newer radiation treatment techniques and limited radiation fields, it is likely that the efficacy of immunotherapy can be maintained when included with conventional treatments. Therefore, there remains an unmet need to better understand the role of immunotherapy alone and in combination with current treatments in lymphoma patients.

A Study on Workload of a Medical Linear Accelerator at a High Throughput Cancer Treatment Centre in Sri Lanka

Radiotherapy bunker design depends on several factors, and among them, workload is one of the important factors. Workload is calculated from the radiation dose delivered at the isocenter. Due to the introduction of new radiotherapy treatment modalities and an increasing number of new cancer patients, there is a higher possibility to increase the workload. Therefore, this study aims to assess the workload of Varian linear accelerator vault at Apeksha Hospital, Maharagama. Data were collected from 1st of August 2020 to 30th November 2020. Dose delivered at isocenter from the 3D-CRT procedures with 6 MV and 15 MV photon energy, the IMRT procedures with 6 MV photon energy and the quality assurance (QA) procedures were collected from ARIA patient management system and transferred into Excel spread sheet for data analysis. The calculated weekly workload was 2326 Gy/week with a 43% contribution from the IMRT procedures with 6 MV, 39% contribution from the 3D-CDT procedures with 6 MV, 16% contribution from the 3D-CDT procedures with 15 MV and 2% contribution from physics workload (QA procedures). The evaluated workload is higher than the NCRP recommended workload of 1000 Gy/week. This study recommends for at least a one-year survey for more accuracy on workload assessment, and also to evaluate the use factor since most of the advanced radiotherapy treatment techniques use high number of monitor units which will increase the leakage radiation.

Spatial and Dosimetric accuracy of 3D polymer gel with CBCT readout - Varian HyperArc® SRS implementation

3D polymer gel dosimetry is a promising means to verify complex radiation treatments such as stereotactic radiosurgery (SRS), as it provides both 3D dosimetric and spatial information. The purpose of the study is to use a polymer gel read-out with cone-beam computed tomography (CBCT) to commission Varian’s HyperArc®-treatment planning and delivery. Three targets (3 cm, 2 cm, 1 cm diameter respectively) were defined on a treatment plan with a maximum dose of 25 Gy, resembling a single isocentre, multiple-lesion SRS plan. Pre- and post-irradiation CBCT images of the gel were obtained for dosimetry analysis. One slice containing two large targets was used to self-calibrate the entire gel volume for dose comparison. We were able to achieve sub-millimeter spatial accuracy and all evaluated gamma criterion (5% 1mm, 3% 1mm, 2% 1 mm were > 95%). In summary, in this study we have demonstrated that CBCT polymer gel dosimetry can be a highly valuable tool for commissioning complex radiation treatment techniques such as SRS.

Technical note: A collision prediction tool using Blender.

Non-coplanar radiotherapy treatment techniques on C-arm linear accelerators have the potential to reduce dose to organs-at-risk in comparison with coplanar treatment techniques. Accurately predicting possible collisions between gantry, table and patient during treatment planning is needed to ensure patient safety. We offer a freely available collision prediction tool using Blender, a free and open-source 3D computer graphics software toolset. A geometric model of a C-arm linear accelerator including a library of patient models is created inside Blender. Based on the model, collision predictions can be used both to calculate collision-free zones and to check treatment plans for collisions. The tool is validated for two setups, once with and once without a full body phantom with the same table position. For this, each gantry-table angle combination with a 2° resolution is manually checked for collision interlocks at a TrueBeam system and compared to simulated collision predictions. For the collision check of a treatment plan, the tool outputs the minimal distance between the gantry, table and patient model and a video of the movement of the gantry and table, which is demonstrated for one use case. A graphical user interface allows user-friendly input of the table and patient specification for the collision prediction tool. The validation resulted in a true positive rate of 100%, which is the rate between the number of correctly predicted collision gantry-table combinations and the number of all measured collision gantry-table combinations, and a true negative rate of 89%, which is the ratio between the number of correctly predicted collision-free combinations and the number of all measured collision-free combinations. A collision prediction tool is successfully created and able to produce maps of collision-free zones and to test treatment plans for collisions including visualisation of the gantry and table movement.

Complication Avoidance of Reconstruction Implant Radiation Therapy (CARIT): A Retrospective Case-Cohort Analysis.

Patients are increasingly offered implant-based reconstruction prior to radiotherapy. However, it is unclear if the radiation treatment technique itself impacts upon toxicity. We performed this study to compare outcomes following implant-based reconstruction amongst breast cancer patients treated with a standard radiotherapy technique that irradiates the entire chest wall versus a novel technique which uses a smaller clinical target volume (CTV) to spare the implant. Need for corrective surgery, capsular contracture, and cosmetic outcomes were evaluated, with the hypothesis that the novel technique would result in fewer adverse outcomes and less need for corrective surgery. A retrospective case-cohort analysis of 57 patients who had post-mastectomy, implant-based reconstruction was conducted. Patients with invasive mammary carcinoma (IMC) or ductal carcinoma in-situ (DCIS) who were treated either with the novel radiotherapy technique (n = 26) or standard PMRT (n = 31) were included. Patient demographics such as age, BMI, TNM stage, implant size, hormone receptor status, and radiation course was collected. Primary endpoint was the need for corrective surgery within two years and cosmetic outcomes, measured using the Baker Classification Scale for capsular contracture and the Modified Harvard Harris Cosmetic Scale. Secondary endpoint was radiation-induced toxicity measured using the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE). Cosmesis and toxicity were evaluated at 3 months post-radiation, 1 year, and after 13 months. Unpaired t-tests were used to compare need for corrective surgery, cosmesis (Baker Grade 2 or higher and Harvard Harris "Good" or worse), and toxicity (NCI CTCAE Grade 2 or higher). For the primary endpoint, need for corrective surgery, there was no significant difference between the novel and standard groups (two-sided p = 0.378, CI -0.38-0.14). The other primary endpoint of cosmesis, measured with the Baker scale and Harvard Harris, was also not significantly different (two-sided p = 0.147, CI -0.06-0.45), with the Harvard Harris cosmesis differences remaining insignificant across the 3 month, 1 year, and greater than 13 month periods (two-sided p = 0.854, 0.351, 0.468, respectively). The secondary endpoint, toxicity, was not significantly different between the novel and standard PMRT groups across 3 months and 1 year time periods (two-sided p = 0.328, 0.323, respectively). We will also be reporting the analysis for predictive factors related to toxicity, need for corrective surgery and cosmesis. Compared with standard PMRT, the novel technique was not significantly different in rates of reoperation, toxicity and cosmetic outcomes. Better understanding the factors involved in PMRT outcomes for breast cancer patients with implant-based reconstructions will aid in the development of standardized approaches to treating the breast cancer patient population.

Barrier films for the prevention of acute radiation dermatitis in breast cancer: A systematic review and meta-analysis of randomised controlled trials.

Radiation dermatitis (RD) is the most common side effect of adjuvant whole-breast or chest wall irradiation, majorly impacting quality of life in numerous patients. The use of barrier films (polyurethane dressings such as Hydrofilm® and Mepitel® film remaining on the skin for the duration of the radiation treatment) has been investigated as a prophylactic measure in several prospective trials. Here, we critically appraise the available evidence behind preventive barrier film application in the context of breast cancer treatment. International literature was reviewed and high-quality randomised controlled trials (RCTs) were included in this meta-analysis. The results of 5 RCTs (663 patients; >90% Caucasian) were analysed. Overall, barrier films lead to improved clinician- and patient-reported outcomes: fewer grade ≥2 RD (11% vs. 42%; OR=0.16; p<0.001) and moist desquamation (2% vs. 16%; OR=0.12; p=0.006), as well as less patient-reported pain (standardised mean difference [SMD] -0.51; p<0.001), itching (SMD -0.52; p=0.001), burning (SMD -0.41; p=0.011), and limitations in daily activities (SMD -0.20; p=0.007). Furthermore, barrier films have a high acceptance rate among patients, as well as a favourable cost-benefit ratio. Possible side effects due to its application are mild and mostly self-limiting. Overall, there was a lack of information on the radiation treatment techniques used. The evidence presented in this meta-analysis suggests that barrier films are an excellent tool in the prevention of RD among Caucasian patients receiving whole-breast or chest wall irradiation. Its use should therefore be considered routinely in these patients.

Comparison of photon intensity modulated, hybrid and volumetric modulated arc radiation treatment techniques in locally advanced non-small cell lung cancer

Background and purposeThere is no consensus on the best photon radiation technique for non-small cell lung cancer (NSCLC). This study quantified the differences between commonly used treatment techniques in NSCLC to find the optimal technique. Materials and methodsTreatment plans were retrospectively generated according to clinical guidelines for 26 stage III NSCLC patients using intensity modulated radiation therapy (IMRT), hybrid, and volumetric modulated arc therapy (VMATC, and VMATV5 optimized for lower lung and heart dose). Plans were evaluated for target coverage, organs at risk dose (including heart substructures) and normal tissue complication probabilities (NTCP). ResultsThe comparison showed significant and largest median differences (>1 Gy or >5%) in favor of IMRT for the mediastinal envelope and heart (maximum dose), in favor of the hybrid technique for the lungs (V5Gy of the total lungs and V5Gy of the contralateral lung) and in favor of VMATC for the heart (Dmean), most of the substructures of the heart, and the spinal cord (maximum dose). The VMATV5 technique had significantly lower heart dose compared to the hybrid technique and significantly lower lung dose compared to the VMATC, combining both advantages in one technique. The mean ΔNTCP did not exceed the 2 percent point (pp) for grade 5 (mortality), and 10 pp for grade ≥2 toxicities (radiation pneumonitis and acute esophageal toxicity), but ΔNTCP was mostly in favor of VMATC/V5 for individual patients. ConclusionThis planning study showed that VMATV5 was preferred as it achieved low lung and heart doses, as well as low NTCPs, simultaneously.

Trends in the Utilization and Outcomes of Brachytherapy vs. Proton Therapy in Localized Uveal Melanoma in the United States

To determine the trends in the utilization of different techniques of radiation treatment in localized uveal melanoma in the United States and to determine the difference in outcome between brachytherapy (BT) and proton-beam therapy (PT). Using the North American Association of Central Cancer Registries (NAACCR), we identified 17451 patients with localized uveal melanoma with known both surgical and method of radiation therapy between 1995-2018. Univariate and multivariable analyses were performed to identify factors and characteristics that may have a potential impact on the treatment. Net survival was calculated using Relative survival in Ederer II cumulative expected method with actuarial. Overall survival (OS) and cancer-specific survival (CSS) were estimated by Kaplan-Meier method and life-tables. The registries included 28.312 patients with uveal melanoma, out of them 22,983 patients with localized disease. Patients with known both surgical and method of radiation therapy were 17451 patients. We have studied this group further. The median age of this group was 61 (IQR 51-71), males were 51.9% (N = 9063), whites were 98.1% (N = 16921), and choroidal tumors were 87.8% (N = 15330). The median tumor thickness was 3.9mm (IQR 24-70), while, the median maximum tumor diameter was 11.3mm (IQR 8.0-14.4). The median follow-up time was 5.9 years (IQR 3.1-10.3). Among all patients, 57.5% (n = 10032) received BT, and 9.8% (n = 1708) received PT. Collectively, 30.1% (n = 5247) of the patients received no radiation treatment. BT constituted 14% of treatment modalities in 1995 and steadily increased to 65% in 2017. PT utilization was minimal in 1995 (1.4%) and also increased to 14.3% in 2017. Younger age and thinner tumor thickness were independently associated with better Cancer-specific survival (CSS) and overall survival (OS). For all patients who were treated primarily with radiation treatment, the 5-year OS was 85,9% and the 10-year OS was 77.2%. There were no differences in rates of OS or CSS between patients who were treated with BT or PT. There is a continuous increase in the utilization of both BT and PT in the treatment of localized uveal melanoma. Similar survival outcomes could be anticipated for both radiation treatment techniques.

Late Toxicity and Patient Satisfaction in Hypofractionated Post-Mastectomy Radiotherapy after Immediate-Autologous Reconstruction

Immediate autologous reconstruction (IAR) is increasingly being used in the context of breast cancer patients (BCP) treated with mastectomy with the need for subsequent radiotherapy treatment. Currently in clinical practice, despite the fact that conventional fractionated RT (CFRT) has been the standard schedule, hypofractionation schemes are becoming increasingly common. Although no results have been reported on tolerance, late toxicity and satisfaction with treatment in this setting. Our aim was to evaluate late side-effects and patient´s satisfaction receiving PMRT after IAR, comparing CFRT vs HFRT. Between June 2015 and February 2020, 47 patients received either CF or HF PMRT after IAR in a tertiary hospital. IAR was performed with latissimus dorsi (LD) or deep inferior epigastric perforator (DIEP) flaps at the time of mastectomy. The prescribed dose was 50 Gy over 25 fractions in the CF schedule and 40.05 Gy over 15 fractions in the HF schedule. The target volume to be treated was the reconstructed chest-wall and the axillary-supraclavicular nodes if indicated, using intensity-modulated radiotherapy treatment technique. Late toxicity was evaluated using CTCAE v.5.0 criteria, and patient´s global satisfaction was assessed using a self-evaluation questionnaire, in which patients answered a series of selected questions related to radiation therapy from the BREAST-Q questionnaire, from 1-5 points. Median age was 48 years (28-77) and median follow-up was 51 months (27-99). 25 patients received HFRT and 22 CFRT. Late side effects after PMRT and tolerance until 3 years with both schedules are shown in Table 1. No relationship was found between incidence of late side effects and RT fractionation. Mean patient´s satisfaction was 3.8 in the CFRT schedule and 4 in the HFRT schedule. According to our findings, HFRT after IAR in post-mastectomy setting seems to be safe and well tolerated, with no high rates of severe late toxicity and with a good level of satisfaction of the treated patients. Table 1. Three years side effects of CRFT and HFRT radiotherapy after mastectomy and immediate autologous reconstruction in 47 patients.

Proton Based Stereotactic Radiotherapy for Skull Base Patients: Dosimetric Comparison to 4 Modern Radiation Treatment Modalities

Re-irradiation with ablative doses to a smaller target volume and strict critical structure constraint is a challenge for modern radiation planning and delivery systems. Several advanced radiation treatment techniques can be used for fractionated stereotactic ablative radiosurgery (FSRS) in select patients with unresectable recurrent head and neck tumors. In this study, in order to better understand the dosimetry advantage of each technique, we compare the stereotactic treatment plans of our new small spot size Hitachi proton treatment unit to those of CyberKnife stereotactic radiosurgery (CK), Gamma Knife radiosurgery (GK), volumetric modulated arc therapy (VMAT), and MR Linac radiotherapy (MRL). Ten FSRS skull base patients treated at our institution using VMAT (n = 5) or GK (n = 5) techniques. Intensity-modulated proton therapy (IMPT) plans were created in Raystation using Monte Carlo dose calculation algorithm. VMAT, CK, GK and MRL plans were generated in RayStation, Accuray Precision, Leksell Gamma Plan, and Monaco treatment planning systems, separately. Planning goals were to achieve the best target coverage of prescribed dose without compromising the critical organs at risk dose volume constraints of the clinical treatment plans. Plans were compared based on percent CTV coverage, Paddick conformity index (PCI), gradient index (GI, V50/V100), dose homogeneity index (HI, (D2-D98)/D50), low dose bath volume (LDBV, ratio of total volume irradiated between 20% and 50% prescription dose and the target volume), beam-on-time (BOT), and mean/maximum doses to brainstems. The median target volume was 15.5 cm3 (range 1.0 - 36.23 cm3). The prescription was 45 Gy in 5 fractions for VMAT patients, and 21 - 27 Gy in 3 fractions for GK patients. The comparison of the treatment plans of these 5 delivery modalities was shown in table. All techniques achieved comparable CTV coverage. GI was superior for GK plans and outstanding in CK and IMPT plans. IMPT plans were also outstanding in regard to BOT and PCI. Significantly improved HI, LDBV and brainstem mean doses were achieved in IMPT plans. For adjacent brainstem and other OARs, maximum doses were comparable among all techniques. In these five advanced radiation therapy modalities, proton therapy SBRT showed dosimetric advantage over other modalities to spare nearby OARs without sacrifice of target coverage. Further studies are needed to utilize this clinical benefit and investigate plan robustness.

Clinical Sequalae of Initial Insurance Denials in a Large Academic Radiation Oncology Center

The objective of this study is to investigate the clinical sequalae of initial radiation oncology insurance denials. The hypothesis is that while the majority of initial insurance case denials are ultimately overturned, there are potential clinical implications to these initial denials. Data were extracted from an institutional registry of patient cases initially denied authorization by their insurers from January 2022 to December 2022. Chi-Square tests using statistical software were employed. Two hundred six cases from November 2021 to December 2022 were identified. The majority (n = 199 [96.6%]) of insurers were commercial payers, while 7 (3.4%) were Medicare/Medicare Advantage. 161 (78.1%) patients were <65 years of age, and 45 (21.8%) 65 or older. One hundred forty-one (68.4%) cases were metastatic, 60 (29.1%) definitive, and 5 (2.4%) were recurrent. Of the 206 cases, 127 (61.6%) cases were ultimately successful in authorization of the ordered treatment without any change to the requested treatment technique or prescription dose after P2P (Peer to Peer review), second-level appeal, comparison plan submission, employer request, insurance carrier change, and/or external appeal, and 56 (27.2%) cases were authorized though with insurer-requested modification to radiation treatment technique and/or prescription dose. Of 21 cases with a requested change in prescription dose, the median decrease in biologically effective dose (BED) was 24 Gy (range: 2.3-51). Of 58 cases with requested change in RT technique, 20 (34.5%) changed from IMRT to 3D-CRT, 16 (27.6%) SBRT to 3D, 15 (25.9%) SBRT to IMRT, 6 (10.3%) SBRT to 2D, and 1 (1.7%) 3D-CRT to 2D. 19 (9.2%) cases remained unauthorized by the insurer but proceeded with treatment via departmental administrative clearance. Of 196 cases which went on to treatment, 72 (36.7%) cases were delayed for a mean of 7.8 days and median of 5 days (range: 1-49). P2P was performed by the treating radiation oncologist in 169 (82.0%) cases, of which 78 (46.1%) were successful in authorization of the ordered treatment. Of the 91 unsuccessful cases, 62 (68.1%) second-level appeals were performed, of which 39 (62.9%) were successful in overturning denied authorization. Of the 23 cases not authorized either through P2P or second-level appeal, 3 (13.0%) cases were successful in authorization of the requested treatment via employer request, external appeal through an independent review organization, or insurance carrier change. Our institutional analysis suggests that while the majority of initial insurance case denials are ultimately overturned without any change to the requested treatment technique or prescription dose through a number of requests made by the insurer to the radiation oncologist, there are clinical implications with a significant percentage of case denials leading to treatment delays, decrease in prescription BED, and less conformal treatment technique.