Conformal Radiotherapy Research Articles

Comparison of the Effectiveness of Radiotherapy with 3D-CRT, IMRT, VMAT and PT for Newly Diagnosed Glioblastoma: A Bayesian Network Meta-Analysis

Background: This study aimed to assess the relative efficacy of modern radiotherapy strategies in patients with newly diagnosed glioblastoma. Method: A comprehensive literature review was conducted through MEDLINE, Embase and the Cochrane Central Registry of Controlled Trials of studies focused on newly diagnosed glioblastoma published up to and counting 15 September 2022. We included randomized controlled trials (RCTs) and comparative nonrandomized studies (NRSs) of radiotherapy for newly diagnosed glioblastoma. Eligible studies included patients treated with three-dimensional conformal radiation therapy, intensity-modulated radiation therapy, volumetric modulated arc therapy or proton therapy reporting either overall survival, progression-free survival or both. The impact of different radiotherapy modalities on survival was evaluated by direct comparisons of indirect evidence and estimated hazard ratios in terms of a Bayesian network meta-analysis. Results: A total of six RCTs or NRSs comprising 816 glioblastoma patients with modern radiotherapy strategies were reviewed, yielding improved overall survival by proton therapy over all other regimens. The network meta-analysis also indicated a significant advantage of proton therapy compared with other radiotherapy strategies in regard to progression-free survival. Conclusion: Our findings suggested PT as a standard RT regime with possibly superior survival outcomes for selected patients with GBM.

Diamond-based detection systems for tomorrow's precision dosimetry

Radiation therapy is now widely applied for cancer care. For an effective and safe treatment, accurate dosimetry is mandatory. The evolution and widespread adoption of modern dynamic and conformal radiotherapy techniques have imposed several challenges from a dosimetric perspective. Commonly employed radiation beams include high-energy (6–18 MeV) photons or electron beams for external treatments, as well as low-energy (tens of keV) photons for intraoperative procedures. Recently, the emerging FLASH technique is posing additional challenges in the field of dosimetry. This work involved the fabrication and test of a custom-made diamond dosimeter. The detector was exposed to high-energy and low-energy X-ray radiation, as well as to FLASH beams, highlighting its versatility under all these conditions. The sensitivity of the dosimeter was estimated to be 73.96 nC Gy−1 mm−3 under MeV photons and 2.76 nC Gy−1 mm−3 under FLASH MeV electrons. Furthermore, this paper aims to illustrate the accuracy of dosimetry using the synchronous detection technique, enabling real-time monitoring of the dose delivered in each pulse, a crucial aspect for the beam diagnostics in the emerging FLASH radiotherapy.

In vivo dose measurements for tangential field-in-field ultra-hypofractionated breast radiotherapy

IntroductionUltra-hypofractionated radiotherapy (UHF-RT) mandates more accuracy in each part of the treatment cycle to maximize cure rates and minimize toxicities. In vivo dosimetry is a direct method for verifying overall treatment accuracy. This study evaluated uncertainties in the delivered dose of Hypofractionated (HF) and UHF Whole Breast Irradiation (WBI) and to analyze the accuracy of the workflow to pave the way for a wide-scale use of UHF-RT. MethodsThirty-three breast cancer cases, including 16 HF-WBI and 17 UHF-WBI were treated with 3D conformal Radiotherapy (3D-CRT), where 79 fields were analyzed for dose verification. The measurement point was set at the beam entrance (1.5 cm depth). The expected dose at Dmax was calculated via TPS. Before in vivo measurements, diode detectors were tested and calibrated. We developed initial validation measurements for UHF-RT on an anthropomorphic breast phantom for the first time. ResultsFor RANDO phantom, the percentage difference between measured and calculated doses showed an average of -0.52 ± 5.4%, in addition to an excellent dose reproducibility within 0.6%. The overall in vivo measurements for studied cases showed that 83.5% of the measured doses were within ±5% and only 1.8% of the measured doses were greater than ±10% of the calculated doses. The percentage accuracy was slightly larger for UHF cohort (84.2%) compared to HF cohort (83.2%). The maximum percentage difference between them was less than 1%. ConclusionBreast in vivo dosimetry is an adequate tool for treatment verification that improves the accuracy of the treatment cycle. UHF-RT may contribute in reducing the long waiting lists, increasing patient convenience, and saving the available resources for breast cancer patients.

Phase II Trial of Five-Fraction Accelerated Partial Breast Irradiation Using Noninvasive Image-Guided Breast Brachytherapy

NIBB has potential advantages over other APBI techniques by delivering highly conformal radiation with minimal collateral dose to the heart and lung compared with external beam techniques, but unlike other brachytherapy techniques NIBB is non-invasive. Previous data has shown encouraging outcomes using a 10-fraction regimen. To improve efficiency, convenience, and cost, reduction in the fraction number is desirable. Final results of a prospective phase II trial are reported. NIBB APBI was delivered using 28.5Gy in 5 fractions daily over 1 week. Patient eligibility criteria required: invasive carcinoma ≤2.0 cm or DCIS ≤3.0 cm, ER positive (if invasive), lymph node negative, LVI absent, and lumpectomy with margins negative by 2mm. The primary endpoint was grade ≥ 2 subcutaneous fibrosis/induration <30%. Secondary endpoints included any late toxicity, cosmetic outcome, and local control. 40 patients were treated with a median follow-up of 59.7 months. The mean age was 67 years (50-89 years) and tumor size was 1.0cm (0.3-2.0cm). 80% had invasive carcinoma. The mean breast separation with compression was 6.7cm (3.5-8.9cm). The 5-year actuarial local control was 96.6% and overall survival was 96.9%. Grade 2 and 3 late toxicities were 15% and 0%, respectively. The rate of grade 2 subcutaneous fibrosis/induration was 2.5% (+/-2.5%) meeting the study's primary endpoint. The most common late toxicity of any grade was skin telangiectasia; 22.5% grade 1 and 15% grade 2. Only breast separation was associated with telangiectasia risk, p=0.002. Overall cosmetic outcome was excellent, good, and fair/poor in 75%, 25%, and 0%, respectively. NIBB APBI delivered in 5 fractions results in a low rate of late toxicity and a high rate of good/excellent cosmetic outcomes. Telangiectasia risk can be minimized by keeping breast separation ≤7.0cm. The local failure rate was appropriately low. Further investigation of this technique is warranted.

Helical Tomotherapy and Melphalan As the Conditioning Regimen in Autologous Stem Cell Transplantation for Multiple Myeloma with Extramedullary Plasmacytoma: A Single Center Clinical Research

Background Multiple myeloma(MM) is the second hematologic malignancy. Extramedullary myeloma indicates a poorer prognosis and survival. High dose Melphalan is the most widely used conditioning regimen. Helical tomotherapy(TOMO) is one of the most advanced intensity-modulated conformal radiotherapy technologies. We applied the combination of TOMO and Melphalan as the conditioning regimen in MM patients, and analyzed its efficacy and safety. Methods Clinical data were collected and compared between TOMO combined with melphalan group and non-TOMO group. SPSS V.25.0 was used for statistical analysis. Results Two methods were not significant difference by statistics analysis. The complete response rate of 100d in non-TOMO group significantly decreased compared to 1 month after transplantation (P=0.001). The 1-year PFS rate in the TOMO group was 86%, while non-TOMO group was 91%. There was no myeloma related death in the two groups within one year. TOMO group showed earlier enter platelet count below 20x109/L (P=0.003) and granulocyte deficiency (P=0.000). In terms of platelet implantation time,TOMO group was superior in platelet implantation time (P=0.041). No atrial fibrillation, heart failure, hepatic small vein occlusion, or transplant related death occurred during the transplantation period. Conclusion: The combination of TOMO and reduced dose Melphalan conditioning regimen is clinically feasible in terms of safety and efficacy evaluation. This scheme could improve the long-term survival of MM patients with extramedullary plasmacytoma.

Long-Term Cause-Specific Mortality in Hodgkin Lymphoma Patients - a Nationwide Danish Cohort Study

Introduction: The documented treatment-induced excess mortality in Hodgkin lymphoma (HL) has led to significant changes in treatment regimens aimed at maintaining efficacy while reducing toxicity. These modifications include the replacement of alkylator-based regimens with anthracycline-based combinations and the adoption of highly conformal radiotherapy. Danish and Nordic radiation oncologists were pioneers in implementing these changes nationwide 10-15 years earlier than most other nations. These early adaptations make Danish HL data uniquely valuable for assessing long-term mortality in a cohort where modern treatment regimens have been implemented nationwide throughout the entire study period. The impact of these treatment modifications on mortality risk in HL survivors remains unclear, therefore, this study aims to assess cause-specific mortality among HL patients treated with contemporary strategies. Methods: This nationwide, unselected study included all HL patients in Denmark aged 15-40 years at diagnosis and treated between 1995 and 2015. Patients were followed from diagnosis until emigration, death, or the study end. HL cases were identified through meticulous individual record reviews of medical records, national registries, and pathology data. Disease-specific death due to HL was the primary outcome, with other cause-specific mortality as a competing risk. Cox proportional hazard models assessed factors influencing overall survival and cause-specific survival. A landmark analysis was conducted to compare the risk of death between the study population and the national background population. Results: Among 1,348 included HL patients, 66.5% had Ann Arbor stage I-II at the time of diagnosis. During 18,731 person-years of follow-up, 139 deaths occurred, resulting in a 5-year overall survival rate of 94.6% (95% CI 93.4-95.8). Factors associated with higher overall mortality risk included older age, advanced disease stage at diagnosis, earlier treatment periods, and exposure to intensive treatment regimens. Causes of death included: HL (71 cases), cardiovascular disease (9 cases), second malignancies (19 cases including 3 hematologic malignancies), bone-marrow transplant-related complications (9 cases), acute treatment-related toxicity (&amp;lt;5 cases), pulmonary diseases (&amp;lt;5 cases), other diseases not related to HL (11 cases), and deaths related to accidents, poisoning or suicide (7 cases). The cumulative risk of mortality due to HL steeply increased over the first 10 years, reaching a plateau at 5.3% at the 10-year mark. Cumulative risk of death due to cardiovascular or pulmonary disease and second cancers had a gradual increase around 10 years after HL diagnosis, but only reached 1.2% and 2.0%, respectively, at the 20-year mark. The cumulative risk of death due to other causes had a slower rise, reaching 2.5% 15 years after diagnosis. Stratifying the cumulative cause-specific risk of death into HL and other causes, we found an initial sharp increase in cumulative risk of death due to HL in the first year after diagnosis, which was surpassed by the risk of death from other causes by 17.8 years of follow-up, with a cumulative risk of death of 5.72%. HL cases had a 7.5-fold higher hazard of mortality compared to the background population. Conclusion: Despite the implementation of contemporary treatment regimes, HL patients still face higher mortality compared to the general population. In the initial years after diagnosis, most deaths are disease-specific, while the risk of mortality due to possible treatment-related late effects gradually increases after 10 years. However, our findings demonstrate a markedly lower overall risk of mortality and cause-specific mortality among HL patients exposed to contemporary treatment, compared to the risk reported in earlier studies among patients from earlier treatment eras (Aleman, B. et al. Long-term cause-specific mortality of patients treated for Hodgkin's disease. J Clin Oncol21 2003, 3431-3439). Furthermore, we observe a remarkably low overall and cause-specific risk of death due to possible treatment-related late effects. The treatment of HL remains a balance between efficacy and toxicity in the individual patient, but our results suggest that recent changes in treatment strategies have led to a distinct reduction in the risk of fatal long-term toxicity and have improved HL-specific survival.

A comparison of the incidence of ≥ grade 2 radiation pneumonitis between intensity-modulated radiotherapy and three-dimensional conformal radiotherapy in patients with unresectable non-small cell lung cancer treated with durvalumab after concurrent chemoradiotherapy.

Intensity-modulated radiation therapy (IMRT) has been increasingly used as a new radiation modality for unresectable non-small cell lung cancer (NSCLC). The risk factors for radiation pneumonitis (RP) during consolidation durvalumab following concurrent chemoradiotherapy (CCRT) using IMRT have not been thoroughly investigated. This retrospective study analyzed medical record data from consecutive patients diagnosed with NSCLC who underwent CCRT and consolidation durvalumab at our institution between April 2018 and September 2022. Since we adopted IMRT for the treatment of NSCLC in April 2020, these patients were categorized into two groups: those treated with IMRT after April 2020 and those treated with three-dimensional conformal radiotherapy (3D-CRT) before April 2020. A total of 31 patients underwent IMRT (the IMRT group), while 25 patients underwent 3D-CRT (the 3D-CRT group). In both groups, the total dose was 60Gy in 30 fractions. The cumulative incidence of ≥ grade 2 RP at 12months was significantly lower in the IMRT group than in the 3D-CRT group (27.0% vs. 64.0%, hazard ratio [HR]: 0.338, 95% confidence interval [CI]: 0.144-0.793, p=0.013). In the multivariable analysis, V20 (≥ 25.6%, HR: 2.706, 95% CI: 1.168-6.269, p=0.020) and radiotherapy technique (IMRT, HR: 0.414, 95% CI: 0.172-0.994, p=0.048) were identified as significant risk factors for ≥ grade 2 RP. IMRT is associated with a lower rate of ≥ grade 2 RP in patients with NSCLC who received CCRT followed by durvalumab.

Dose to Organ at Risk and its Characteristic Variation with the Clinically Used Different Prescription Levels for Early-stage Left-sided Breast Cancer

AimsTo evaluate the organ at risk (OAR) dose and its characteristic variation with different clinically usable prescription doses (RxD) for breast and chest wall radiotherapy in patients with early-stage left-sided breast cancer. Materials and methodsIn total, 145 patients with early-stage breast cancers (T1N0M0-T2N0M0) on the left side were treated with radiotherapy after a modified radical mastectomy or breast conservation surgery, with a mean age of 45.1 ± 21.6 years. The patient received 4050 cGy of field-in-field (three-dimensional conformal radiotherapy) treatment limited to the breast or chest wall, excluding the supraclavicular node, axillary node and internal mammary chain, over 15 fractions. Additional plans of 5000 cGy/25 fractions, 4500 cGy/20 fractions and 2600 cGy/5 fractions were created with no or minor changes to the original plan. Mathematical modelling was used to study the distinctive change in the dose–volume characteristics for various OARs as a function of the RxD. OAR dosages, both absolute and normalised, were expressed in terms of the RxD. The mathematical (functional) relationship between OAR doses and different prescription levels was deduced by the least squares fit method. ResultThe left lung mean dose, V5Gy (%), V10Gy (%) and V20Gy (%) and the heart mean dose, V10Gy (%) and V20Gy (%) were evaluated. The dose–volume parameters showed a parabolic variation (x2) with the RxD. Prescription normalised OAR doses showed a linear relationship with the RxD; relative dose increased with diminishing RxD. Normalised lung and heart mean doses exhibited saturation (linear relationship) with RxD variation. Paired sample t-test results between RxD versus all evaluated parameters were found to be statistically significant (P = 0.004). The Pearson correlation coefficient between different prescription levels for left lung mean dose (range 0.942–1.0), heart mean dose (range 1.0–1.0), left lung V5Gy (%) (range 0.987–1.0), left lung V10Gy (%) (range 0.991–0.999), heart V10Gy (%) (range 0.998–1.0). ConclusionThe functional form of absolute OAR dose–volume parameters versus RxD is parabolic and the RxD normalised OAR dose–volume parameter versus RxD is a straight line with a negative slope as RxD increases. This indicates an increase in the relative OAR dose–volume parameters if the RxD is reduced. This study is the first of its kind to compare the OAR doses as a function of clinically used degenerate prescription levels. These data will help to comprehend the OAR doses while adopting a new dose fractionation regimen and reviewing the radiotherapy treatment plans.

Study of The Effect of Using Modulated Intensity Radiotherapy Compared to Three Dimension Conformal Radiotherapy on Urinary Bladder Tumors

Study of The Effect of Using Modulated Intensity Radiotherapy Compared to Three Dimension Conformal Radiotherapy on Urinary Bladder Tumors

Pre-treatment Evaluation of Patients Eligible for Whole Brain Radiation Therapy: The Risk of Hippocampal Metastases in a Retrospective Study of 248 Cases at a Single Institution.

Whole brain radiation therapy (WBRT) is effective for multiple brain metastases (BMs) but may impair neurocognitive function (NCF). The incidence of hippocampal metastasis (HM) is low, and the factors associated with the occurrence of HM remain unclear. This study aimed to assess the occurrence of limbic system metastasis (LSM), including HM, and to analyze the risk of HM. We retrospectively analyzed 248 patients who underwent three-dimensional conformal radiation therapy for BMs between May 2008 and October 2015. Gadolinium-enhanced brain MRI or CT scans were used for diagnosis. Statistical analysis involved assessing clinical factors, including age, gender, primary tumor, number of BMs, and maximum metastasis diameter, in relation to the presence of HMs using logistic regression and receiver operating characteristic (ROC) curve analysis. The median age at treatment was 62 years (range: 11-83 years). Primary lesion sites included the lung (n = 150; 60.5%), breast (n = 45; 18.1%), gastrointestinal tract (n = 18; 7.3%), and bone and soft tissue (n = 2; 0.8%). Histological cancer types included adenocarcinoma (n = 113; 45.6%), squamous cell carcinoma (n = 26; 10.5%), small cell carcinoma (n = 28; 11.3%), invasive ductal carcinoma (n = 35; 14.1%), sarcoma (n = 3; 1.2%), and others (n = 43; 17.3%). MRI or CT scans of the 248 patients were analyzed, indicating a total count of 2,163 brain metastases (median: five metastases per patient). HMs were identified in 18 (7.3%) patients. The most common location for LSMswas the cingulum/cingulate gyrus in 26 (10.5%) patients. In univariate and multivariate analyses, patients with 15 or fewer BMs had a significantly lower incidence of HMs (odds ratio (OR), 0.018 (95% confidence interval (CI), 0.030-0.24)) (p < 0.0001). A maximal tumor size of less than 2cm significantly increased the incidence of HMs (OR, 13.8 (95%CI, 1.80-105.3)) (p = 0.0003). The presence of cingulum/cingulate gyrus metastases also demonstrated a significant increase in the incidence of HMs (OR, 9.42 (95%CI, 3.30-26.84)) (p < 0.0001). The present study has uncovered a novel association between a high number of metastases in the cingulate gyrus and the development of HMs. Patients with BMs eligible for WBRT with metastases in the cingulate gyrus may be at risk of developing HM.

Economical Evaluation of Prostate Cancer Treatment Using Intensity-Modulated Radiation Therapy, 3-Dimensional Conformal Radiation Therapy and Radical Prostatectomy: A Systematic Review

ObjectivesProstate cancer is a common form of cancer among men worldwide. The objective of this study was to conduct a systematic review of the economic evaluations of prostate cancer treatment strategies. MethodsThis systematic review was conducted using multiple electronic databases up to May 2021. English-language economic evaluation studies that compared intensity-modulated radiation therapy (IMRT), 3-dimensional conformal radiation therapy (3DCRT), and radical prostatectomy (RP) were included. The studies were evaluated using the Consolidated Health Economic Evaluation Reporting Standards checklist. The search yielded 1151 potentially relevant publications, which were screened based on the title and abstract. After the removal of duplicates, 55 studies remained, and 9 studies were screened in full text. Finally, textual data were analyzed manually using by-content analysis method. ResultsAll studies were cost-effective and evaluated quality-adjusted life year as the efficacy indicator. The studies were conducted from either payers' or health systems' perspectives, and the time horizon varied from 5 to 20 years. We included only full economic evaluation studies. The use of IMRT in comparison with 3DCRT was evaluated in 6 studies, based on which IMRT increased health and reduced side effects of treatment. According to incremental cost-effectiveness ratio (ICER) results, IMRT was more cost-effective than 3DCRT. Three studies evaluated the use of RP in comparison with radiotherapy. Based on these studies, radiotherapy was more effective than RP. ConclusionIMRT was found to be more cost-effective than 3DCRT in all 6 studies compared with the threshold. Radiotherapy was found to be more effective than RP. However, long-term clinical trial studies are needed to confirm these findings and to provide more definitive conclusions.

Comparison of Acute Gastrointestinal Toxicity of Intensity-Modulated Radiotherapy Versus Three-Dimensional Conformal Radiotherapy in Patients of Carcinoma Cervix.

Introduction Cervical cancer is the most common gynaecological malignancy worldwide, with a higher prevalence in middle- and low-income countries. Chemoradiotherapy, followed by intracavitary brachytherapy, is the treatment of choice in locally advanced cervical cancer. The most common acute side effect of external beam radiotherapy (EBRT) is bowel toxicity in the form of diarrhoea and abdominal cramps. The treatment techniques of EBRT were revolutionised with the advent of intensity modulation. This study aims to prospectively analyse whether the dosimetric advantage of intensity-modulated radiotherapy (IMRT) over three-dimensional conformal radiotherapy (3DCRT) is translated clinically into a decrease in acute toxicity. Method Twenty-four patients were randomised into two groups: the 3DCRT and the IMRT. Acute gastrointestinal (GI) toxicity was assessed during treatment using radiation therapy oncology group grading. The factors under consideration were age, stage of the disease, treatment technique, chemotherapy, and the intention of therapy (radical or adjuvant). The mean bowel bag dose of the two techniques was analysed. Result Among the factors under consideration, it was found that the treatment technique was the only factor that had a significant association with acute bowel toxicity in both univariate (p = 0.036) and multivariate analyses (p = 0.028). The mean V25 (the volume receiving 25 Gy), V45, and V50 of the bowel bag in the IMRT arm were significantly less than the 3DCRT arm. Grades 2 and 3 acute bowel toxicities were also higher in the 3DCRT arm. Conclusion The treatment technique is essential to determining acute GI toxicity during pelvic radiotherapy. With IMRT, the dose to the bowel bag and, in turn, the acute bowel toxicity can be reduced.

Radiation therapy of breast cancer in the Nahe Breast Center: first results of an analysis in the context of health services research.

The first evaluation of radiotherapy results in patients with breast cancer treated as part of amultimodal oncologic therapy in the Nahe Breast Center is presented. Analysis of the results was performed using an in-practice registry. From September 2016 to December 2017, 138 patients (median age 62.5years; range 36-94years) with breast cancer (right side, n = 67; left side, n = 71) received adjuvant radiation therapy. Of these, 103 patients received gyneco-oncologic care at the Nahe Breast Center, and 35were referred from outside breast centers. The distribution into stages was as follows: stageI, n = 48; stageII, n = 68; stageIII, n = 19; stageIV, n = 3. Neoadjuvant chemotherapy was given to 19and adjuvant chemotherapy to 50patients. Endocrine treatment was given to 120 patients. Both 3D conformal (n = 103) and intensity-modulated (n = 35) radiotherapy were performed with amodern linear accelerator. With amedian follow-up of 60months (1-67), local recurrence occurred in 4/138 (2.9%) and distant metastasis in 8/138 (5.8%) patients; 7/138 (5.1%) patients died of their tumors during the follow-up period. The actuarial 5‑year local recurrence-free survival of all patients was 97.1%, and the actuarial 5‑year overall survival of all patients was 94.9%. We observed no grade3 or4 radiogenic side effects. The results of radiotherapy for breast carcinoma at the Nahe Breast Center are comparable to published national and international results. In particular, the local recurrence rates in our study, determined absolutely and actuarially, are excellent, and demonstrate the usefulness of radiotherapy.

SURG-31. DEFINING THE NEW POSSIBILITIES FOR CESIUM BRACHYTHERAPY IN PATIENTS WITH PERIVENTRICULAR GBM

Abstract INTRODUCTION Re-irradiation of patients with external beam radiotherapy (EBRT) for recurrent glioblastoma (GBM) continues to present a therapeutic dilemma due to a high risk of radiation induced necrosis (RN). In contrast, brachytherapy represents a safer, more conformal radiation option aimed at optimizing local control while minimizing the risk of brain tissue damage. Immediate intra-operative implantation with brachytherapy prevents tumor repopulation and offers patients two procedures in one setting. However, due to the risk of seed migration, surgical resection and brachytherapy in periventricular regions was deemed unachievable. In heavily pretreated periventricular GBM, where further EBRT is complicated by RN, a barrier between the ventricular lining and tumor cavity is needed to prevent seed migration. We present two patients where such a barrier allowed successful implantation of brachytherapy to improve disease control. METHODS Two patients, previously treated with surgery and EBRT, presented with recurrent GBM abutting the ventricles. Following GTR of the tumors, a barrier was created by patching the ventricle with Gelfoam to prevent seed migration. Intraoperative brachytherapy implantation of suture stranded Cs-131 seeds (Isoray) for patient 1 and collagen embedded Cs-131 (GammaTile) for patient 2 was performed. A total of 20 Cs-131 seeds on strings threaded through Surgicel, and 6 GammaTiles (24 Cs-131 seeds), were used implanted in patients 1 and 2, respectively. Surgicel covered the implanted seeds and the resection cavity filled with Adherus. RESULTS Post-operative CT scan demonstrated all 20 Cs-131 seeds and 24 Cs-131 seeds in the surgical cavities of patients 1 and 2, respectively, and had serial post operative imaging with MRI scans showing Cs-131 seeds layering surgical cavity, as late as 6 months in total follow up. To date, both patients have had durable local control and no seed migration.

Accelerated three-dimensional conformal radiotherapy for early-stage glottic cancer in reducing dose to the internal carotid artery and pharyngeal constrictor muscles.

We evaluated clinical and dosimetric outcomes of radiotherapy using two anterior oblique portals (AOP), to reduce the dose to the bilateral internal carotid arteries (CAs) and pharyngeal constrictor muscle (PCM) during early-stage glottic cancer (ESGC) treatment. We identified patients with ESGC who underwent definitive radiotherapy between June 2014 and May 2020. Among the 66 patients, 32 (48%) underwent radiotherapy using AOP, and the remaining underwent typical radiotherapy using parallel opposed lateral portals (POLP). The median follow-up duration was 53 months. No significant differences were observed in the 5-year local failure (0%/9.4%), progression-free survival (90.6%/90.8%), and overall survival (90.6%/91.0%) rates between the two groups. The grade ≥2 acute mucositis incidence rate was significantly lower in the AOP group (44%/85%). Radiotherapy using AOP maintained an adequate dose coverage to the target while markedly reducing the CAs and PCM doses. Radiotherapy with AOP resulted in favorable clinical and dosimetric outcomes.

Dosimetric comparison of four-dimensional computed tomography based internal target volume against variations in respiratory motion during treatment between volumetric modulated arc therapy and three-dimensional conformal radiotherapy in lung stereotactic body radiotherapy.

This study focused on the dosimetric impact of variations in respiratory motion during lung stereotactic body radiotherapy (SBRT). Dosimetric comparisons between volumetric modulated arc therapy (VMAT) and three-dimensional conformal radiotherapy (3DCRT) were performed using four-dimensional computed tomography (4DCT)-based internal target volumes (ITV). We created retrospective plans for ten patients with lung cancer who underwent SBRT using 3DCRT and VMAT techniques. A Delta4 Phantom + (ScandiDos, Uppsala, Sweden) was used to evaluate the dosimetric robustness of 4DCT-based ITV against variations in respiratory motion during treatment. We analyzed respiratory motion during treatment. Dose-volume histogram parameters were evaluated for the 95% dose (D95%) to the planning target volume (PTV) contoured on CT images obtained under free breathing. The correlations between patient respiratory parameters and dosimetric errors were also evaluated. In the phantom study, the average PTV D95% dose differences for all fractions were - 2.9 ± 4.4% (- 16.0 - 1.2%) and - 2.0 ± 2.8% (- 11.2 - 0.7%) for 3DCRT and VMAT, respectively. The average dose difference was < 3% for both 3DCRT and VMAT; however, in 5 out of 42 fractions in 3DCRT, the difference in PTV D95% was > 10%. Dosimetric errors were correlated with respiratory amplitude and velocity, and differences in respiratory amplitude between 4DCT and treatment days were the main factors causing dosimetric errors. The overall average dose error of the PTV D95% was small; however, both 3DCRT and VMAT cases exceeding 10% error were observed. Larger errors occurred with amplitude variation or baseline drift, indicating limited robustness of 4DCT-based ITV.

Interplay of Oncoplastic Reconstruction and Adjuvant Radiation Therapy in Breast Cancer

PurposeOncoplastic breast surgery (OBS) combines breast cancer tumor removal with the cosmetic benefits of plastic surgery at the time of breast conserving surgery. Potential advantages of OBS include wider surgical margins around the tumor bed, while the natural shape and appearance of the breast are maintained more than standard lumpectomy procedures. However, limited information is available regarding the potential impact on adjuvant radiation treatment planning. Materials and MethodsWomen with localized breast cancer undergoing lumpectomy with immediate OBS and adjuvant radiation therapy between 2014 and 2019 were reviewed. OBS was performed utilizing volume displacement techniques and patients received whole breast irradiation with three-dimensional conformal radiation therapy. ResultsVolume of additional ipsilateral breast tissue removed during OBS ranged from 21-2,086 cm3 (median 304 cm3), 29% of patients had >500 cm3 of tissue removed. Surgical margins were positive in 12.5% and were not affected by volume of breast tissue removed (445 vs 439 cm3). Patients with surgical clips more often received a lumpectomy bed boost (75.9% versus 50.0%), boost volumes were on average 157 cm3 with clips versus 205 cm3 without clips. Mean V105 was comparable in patients with >500 cm3 tissue removed and irradiated breast volume >1,000 cm3, while higher absolute volumes were found in patients with >26 cm posterior separation (58.0 cm3 vs 102.7 cm3, p=0.07). No meaningful difference was observed in Dmax or radiation coverage (95% of the volume receiving 95% of the prescription dose) for patients with >26 cm posterior separation, >500 cm3 of breast tissue removed, or irradiated breast volume >1,000 cm3. ConclusionRadiation dosimetry plans for patients undergoing oncoplastic surgery were acceptable and no significant radiation or surgical advantage was gained in patients with more tissue removed. Our study stresses the importance of clear communication between surgeons and radiation oncologists about sufficient marking of the lumpectomy cavity, utilizing practices that minimize the need for re-excisions, and minimizing lumpectomy cavity disruption during rearrangement.

An Analytical Study to Determine Dose-Volume Threshold for Radiation Induced Hypothyroidism.

Objective: To determine radiation dose volume threshold in predicting the development of hypothyroidism in cancer patients following neck irradiation. Methods: This is a cross sectional follow up study for patients who had been previously irradiated, prior to enrolment in the study. We have done thyroid dose-volumetric analysis on 120 histologically proven cancer patients in the age group of 18-75 years who received neck irradiation as a part of their definitive or adjuvant radiotherapy with three-dimensional conformal or intensity-modulated radiotherapy technique (3D -CRT or IMRT) and completed at least six months post-radiotherapy. Primary tumor sites included carcinoma or lymphoma of the head and neck, breast, cervical, and upper thoracic esophagus, requiring neck irradiation. Results: The proportion of patients who tested positive for Radiation induced hypothyroidism (RIHT) was found to be 40%, with clinical hypothyroidism and subclinical hypothyroidism being 25.8% and 14.2%, respectively. Time to develop hypothyroidism peaks around two years. Mean thyroid gland dose (Dmean) >28 Gy, thyroid gland volume receiving 40 Gy dose (i.e. V40) >49% and age <50 years were found to be significant risk factors for the development of RIHT on binary logistic regression. RT dose >50 Gy and thyroid gland volume spared from 40 Gy (i.e. VS40) < 2.12cm3 were statistically significant predictors for RIHT on chi-square and (Receiver operating characteristic) ROC curve analysis respectively but not on regression analysis. Conclusion: Dose-volume threshold for the thyroid gland as Dmean <28 Gy and V40 <49% may prevent the development of RIHT.

Polymer gel dosimetry for experimental verification of conformal small animal irradiation at a preclinical research platform

In translational research, there is a need for preclinical studies of high quality that corresponds to the conformal dose distributions conventionally delivered to humans in the modern radiotherapy clinic. To facilitate this need, novel preclinical systems consist of preclinical radiation platforms and small animal treatment planning systems. However, small-field dosimetry is challenging and requires dosimeters with high spatial resolution. In this study we demonstrate the feasibility of experimentally validating the dose distribution in small fields at a preclinical X-ray research platform using a polymer gel dosimeter and MRI-readout.

A Retrospective Comparison of Toxicity, Response and Survival of Intensity-Modulated Radiotherapy Versus Three-Dimensional Conformal Radiation Therapy in the Treatment of Rectal Carcinoma

A Retrospective Comparison of Toxicity, Response and Survival of Intensity-Modulated Radiotherapy Versus Three-Dimensional Conformal Radiation Therapy in the Treatment of Rectal Carcinoma