Dosimetric evaluation of right coronary artery in radiotherapy for breast cancer

Comparison with control groups of untreated patients suggests that right-breast-cancer patients who receive radiotherapy have a higher rate of heart disease. Dose constraint for heart has been established to minimize radiotherapy-induced cardiotoxicity during left breast cancer treatment. Additionally, it is suggested to minimize the dosage on left anterior descending (LAD) artery. Right coronary artery (RCA), is the second largest artery, after left main coronary artery, supplying the heart. A dose evaluation study is not present for RCA; the proximal part of which is included in the irradiation field during breast cancer treatment of right breast. To investigate the presence of a correlation, doses resulting from right and left breast radiotherapy on proximal RCA (pRCA), LAD, and heart are evaluated in this study. Forty breast cancer patients who went under breast-conserving surgery are the subject of this study. Four groups were established; right breast, right breast and internal mammary (IM), left breast and left breast, and IM. pRCA, LAD, and heart volumes were contoured for each group on the planning tomographies. Resultant doses of tangential fields planning on these volumes were compared using dose-volume histograms. Mean and maximum doses of pRCA were statistically compared between groups. The highest mean and maximum point doses (192 to 284 cGy) were found in the right breast + IM group (p < 0.05). The mean and maximum doses only in the right breast and left breast + IM group did not differ statistically. However, the mean and maximum pRCA doses in these 2 groups were higher than only the left breast group (p < 0.05). pRCA receives high doses during radiotherapy of right and left breast especially if IM is included. This may predispose to coronary artery disease.     

Use of Specific Duodenal Dose Constraints During Treatment Planning Reduces Toxicity After Definitive Paraaortic Radiation Therapy for Cervical Cancer

PurposeThis study aimed to validate the safety of paraaortic nodal (PAN) radiation therapy (RT) for patients with cervical cancer when the duodenal dose is limited to V₅₅ < 15 cm³ and V₆₀ < 2 cm³.Methods and MaterialsA total of 97 patients who were treated with RT for cervical cancer between 2010 and 2018 received at least 56 Gy to grossly involved PANs. Patients were treated with concurrent chemoradiation (n = 88; 91%), with 93% of patients (n = 90) receiving intensity modulated RT to the initial PAN field and 98% (n = 95) receiving intensity modulated RT to a sequential PAN boost. The V₅₅ < 15 cm³ and V₆₀ <2 cm³ criteria were implemented in 2014. Normal tissues were contoured on computed tomography (CT) simulation data sets, and the duodenum was contoured from the gastric outlet to the duodenojejunal flexure. Sixty-six patients (68%) had a resimulation scan after approximately 20 fractions. Composite duodenal doses were calculated using the initial CT scan for 50 patients (52%) and the resimulation CT scan for 47 patients (48%) depending on the anatomic changes throughout treatment.ResultsThe median duodenal V₅₅ was 3.5 cm³ (interquartile range [IQR], 0.2-8.1 cm³) and the median V₆₀ was 0.3 cm³ (IQR, 0.0-1.8). Constraints were exceeded in 18 patients, of whom 16 patients (89%) had been treated before 2014. Treatment for the 2 patients treated after 2014 was complicated by significant weight loss and reduced anterior-posterior diameter, which likely overestimated the true dose on the composite plan. Only 1 patient experienced grade 3 duodenal toxicity (stricture requiring endoscopic balloon dilation 3 months after treatment); however, the stricture was outside of the high-dose boost volume, and the patient had a history of gastritis. Six patients (6%) had a first recurrence within the PAN region.ConclusionsLimiting the duodenal dose to V₅₅ < 15 cm³ and V₆₀ < 2 cm³ for patients with cervical cancer and PAN involvement is feasible, and minimizes duodenal toxicity while maintaining acceptable local control rates.     

Quality and Safety Considerations in Stereotactic Radiosurgery and Stereotactic Body Radiation Therapy: An ASTRO Safety White Paper Update

PurposeThis updated report on stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT) is part of a series of consensus-based white papers previously published addressing patient safety. Since the first white papers were published, SRS and SBRT technology and procedures have progressed significantly such that these procedures are now more commonly used. The complexity and submillimeter accuracy, and delivery of a higher dose per fraction requires an emphasis on best practices for technical, dosimetric, and quality assurance. Therefore, quality and patient safety considerations for these techniques remain an important area of focus.MethodThe American Society for Radiation Oncology convened a task force to assess the original SRS/SBRT white paper and update content where appropriate. Recommendations were created using a consensus-building methodology and task force members indicated their level of agreement based on a 5-point Likert scale, from “strongly agree” to “strongly disagree.” A prespecified threshold of ≥75% of raters who select “strongly agree” or “agree” indicated consensus.SummaryThis white paper builds on the previous version and uses of other guidance documents to broadly address SRS and SBRT delivery, primarily focusing on processes related to quality and safety. SRS and SBRT require a team-based approach, staffed by appropriately trained and credentialed specialists as well as significant personnel resources, specialized technology, and implementation time. A thorough feasibility analysis of resources is required to achieve the clinical and technical goals and thoroughly discussed with all personnel before undertaking new disease sites. A comprehensive quality assurance program must be developed, using established treatment guidelines, to ensure SRS and SBRT are performed in a safe and effective manner. Patient safety in SRS/SBRT is everyone's responsibility and professional organizations, regulators, vendors, and end-users must demonstrate a clear commitment to working together to ensure the highest levels of safety.     

Indications for Adjuvant Radiation Therapy in Patients With pN0(i +) Adenocarcinoma of the Endometrium

Sentinel lymph node biopsy has led to an increase in the detection of isolated tumor cells (ITCs) in up to 10% of early stage endometrioid endometrial cancer patients. In addition, the risk of nonsentinel lymph node involvement is approximately 10% or lower in patients with ITCs. In most studies, approximately 60% to 70% of patients with ITCs either underwent completion lymphadenectomy or received adjuvant therapy. Therefore, although multiple studies have shown that the effect of ITCs on disease outcomes is favorable, the true effect of ITCs without additional treatment is not known. In this report we describe our philosophy of relying on extent of surgical nodal staging and presence or absence of adverse intrauterine pathologic factors at the time of adjuvant therapy decision making for endometrioid endometrial carcinoma patients with ITCs.     

应用自行研制的运动模体研究呼吸状态改变对立体定向门控放疗的影响

目的 评价患者呼吸状态的改变对实时位置监测系统(RPM)引导下自由呼吸立体定向门控放疗影响。方法 通过自行研制运动模体模拟患者治疗过程中出现基线偏移,呼吸频率改变,呼气末延时、吸气末延时,以及不规则呼吸情况,并分析三维适形、固定野动态调强、单弧旋转调强3组计划各状态变化与模体中心小球位置(L)及电离室受照剂量的相关性。结果 自研模体的摆位重复性和测量稳定性良好。L与基线偏移呈现正相关(r=0.99,P＜0.01)。基线偏移小于摆位误差时,剂量变化在4%以内,相对较小,超出后受照剂量快速下降并呈现负相关(r= -0.95,P＜0.01),偏移超出与不超出摆位误差时所测得的受照剂量,差异具有统计学意义(Z= -3.06,P<0.01)。3组计划受基线偏移的影响率差异无统计学意义(P>0.05)。呼吸频率改变对 L 和剂量影响较小。吸气末延迟和呼气末延迟都导致3组计划剂量下降,最大达-1.74%,同时吸气末延迟相对呼气末延迟影响更大,差异具有统计学意义(Z= -2.67,P<0.01),但延迟时间长短对剂量的影响率没有明显相关性(P＞0.05),3组计划受波形改变的影响率差异无统计学意义(P＞0.05)。不规则呼吸对剂量影响较大,3组计划重复测量6次受照剂量分别为三维适形(709.68±180.00)cGy;固定野动态调强(751.40±127.16)cGy;单弧旋转调强(750.00±185.60)cGy,均小于处方剂量,一致性欠佳。结论 患者呼吸状态改变会导致剂量下降,基线偏移超出摆位误差阈值或者波形变异较大出现不规则呼吸时更甚,且与放疗技术不相关。     

TrueBeam加速器射野准直器跟随功能在鼻咽癌固定野调强放疗和容积旋转调强放疗中的应用’

目的：研究TrueBeam加速器的射野跟随功能在鼻咽癌固定野调强放疗和容积旋转调强放疗中的作用;方法：随机选取10例鼻咽癌患者．分别对每位患者设计四个计划．分别为固定野调强组的dIMRT-JT和dlMRT计划,容积旋转调强组的RapidArc—JT和RapidArc计划。dIMRT-JT和RapidAre-JT为使用射野跟随功能的计划,dIMRT和RapidArc为不使用射野跟随功能的计划。分别比较使用和不使用射野跟随功能的治疗计划．患者靶区和危及器官的剂量学差异;结果：固定野调强计划,在使用和不使用射野准直器跟随功能,其靶区的剂量学参数差别不大,但是脑干、脊髓、晶状体、腮腺等危及器官都有较大改善,脑干和脊髓的D,。剂量分别降低了3．3％和4．2％,左、右两侧晶状体的D。剂量分别降低了38．7％和40．6％,左、右两侧腮腺的平均剂量D一分别降低了6．3％和6．4％;P〈0．05,有统计学意义。容积旋转调强计划,在使用和不适用射野准直器跟随功能时,靶区和脑干、脊髓及腮腺等危及器官的剂量学差异很小,没有统计学意义;而左、右两侧晶状体的D。剂量分别降低了6．9％和7．2％;结论：鼻咽癌固定野调强放疗和容积旋转调强放疗中,使用TrueBeam加速器的射野准直器跟随功能,可以在保证靶区剂量分布不变的前提下,降低危及器官的受照剂量。尤其在固定野调强放疗中,使用射野准直器跟随功能的计划其剂量学优势非常明显。     

kV-Cone Beam CT as an IGRT Tool in the Treatment of Early Stage Prostate Cancer: A Literature Review

Image-guided radiation therapy (IGRT) is an important quality assurance measure that can be used in tandem with conformal radiation therapy treatment. Cone beam computed tomography (CBCT) is a sophisticated IGRT technology that has recently been introduced to the clinical setting. Cone beam equipment includes kilovoltage (kV) CBCT that produces online, high-quality, three-dimensional images of the prostate gland. Interfractional displacements of the prostate can be quantified and adjustments made using kV-CBCT so that daily RT can be accurately delivered. In addition, the volumetric nature of CBCT allows deformations of the prostate gland and surrounding anatomy to be accounted for using adaptive radiation therapy strategies.This article provides an introduction to the main IGRT tools that can be used in parallel with conformal radiation therapy of prostate cancer. A literature review is performed to describe the major IGRT approaches; however, the focus will remain primarily on the technical and clinical applications of kV-CBCT. Important considerations including patient dose, resource implications, and possible changes to the radiation therapist's scope of practice are also discussed.