三种不同优化方法在局部晚期宫颈癌腔内联合组织间插植近距离治疗计划中的剂量学比较

目的 比较分析局部晚期宫颈癌腔内联合组织间插植近距离治疗计划3种优化方法的剂量学差异。方法 回顾性选取局部晚期宫颈癌患者20例,对每例患者根据不同优化方法,分别制定3种计划,分别为手动计划组,基于图形优化;逆向1计划组,基于模拟退火优化算法;逆向2计划组,在逆向1组基础上增加了靶区（CTV）最大剂量限定。比较计划中CTV的体积剂量参数V₂₀₀、V₁₅₀、V₁₀₀、D₁₀₀、D₉₀、均匀性指数（HI）,以及直肠、膀胱、乙状结肠的剂量参数D_{0.1 cm³}、D_{1 cm³}、D_{2 cm³}。结果 CTV方面,手动组和2个逆向组的D₁₀₀参数差异无统计学意义（P>0.05）,但2个逆向组的V₂₀₀、V₁₅₀、V₁₀₀、HI参数明显优于手动组（t=-3.422~9.910,P<0.05）。逆向1组的V₁₀₀和D₁₀₀优于逆向2组（t=7.238、5.032,P<0.05）。危及器官（OARs）方面,与手动组相比,2个逆向组中直肠、膀胱、乙状结肠的D_{0.1 cm3}、D_{1 cm³}和D_{2 cm³}明显降低（t=2.235~5.819,P<0.05）。结论 对于局部晚期宫颈癌腔内联合组织间插植技术,基于3组优化方法的计划均能满足临床需求,且使用逆向优化方法保证了靶区剂量覆盖,同时减少直肠、膀胱、乙状结肠的最大受量。     

宫颈癌腔内联合组织间插植近距离治疗优化算法剂量学分析研究

目的在宫颈癌腔内联合组织间插植近距离治疗(IC/ISBT)中, 基于剂量学及生物学模型的帮助, 进行图形优化(GO)、模拟退火逆向计划优化算法(IPSA)和混合逆向计划优化算法(HIPO)的比较分析, 为宫颈癌IC/ISBT治疗优化方法的选择提供依据。方法选取65例接受影像引导下IC/ISBT的宫颈癌患者。所有患者后装治疗计划分别采用GO、IPSA、HIPO优化的方式制定3次, 处方剂量高危临床靶区体积(HRCTV)D90均为6 Gy。针对3种优化方案的用时、剂量-体积参数及放射生物学差异, 采用非参数Friedman检验以及非参数Wilcoxon秩检验进行比较分析。结果逆向计划优化耗时均较正向计划耗时短, 时间分别是GO 135.03 s、IPSA 46.53 s、HIPO 98.36 s, 肿瘤靶区剂量中高剂量照射的V150%(53.66%)在HIPO计划中略高, 而高剂量照射的V200%(30.29%)在GO计划中更高。GO的适形度指数(CI)(0.91)较其他计划更好, 差异具有统计学意义(χ2=69.98, P<0.001)。HIPO计划的膀胱与直肠的D1 cm3、D2...     

宫颈癌腔内联合组织间插植近距离后装治疗中IPSA和HIPO逆向优化算法的比较分析

目的 比较宫颈癌腔内联合组织间插植三维后装计划中模拟退火逆向优化（IPSA）和混合逆向优化（HIPO）剂量分布的差异,为宫颈癌腔内联合组织间插植后装治疗逆向计划优化方法的选择提供依据。方法 选取2016年12月至2017年5月于河北省沧州中西医结合医院43例宫颈癌患者资料,所有患者原后装治疗计划采用IPSA优化,基于原图像信息,给定同样的初始约束条件,不进行手动优化,直接计算IPSA和HIPO计划,对高危靶区（HR-CTV）剂量体积参数D₉₀、D₁₀₀、V_100%,以及均匀性指数（HI）、适形指数（CI）、危及器官（OAR）（膀胱、直肠和乙状结肠）D_{2 cm³}的数据进行评价。结果 两组间HR-CTV的D₉₀、D₁₀₀以及CI剂量差异无统计学意义（P>0.05）,但HIPO组HR-CTV的V_100%为（87.72±0.49）%;HI为（0.51±0.08）,明显高于IPSA组的（85.01±0.55）%,HI（0.42±0.06）,差异具有统计学意义（t=2.54、3.02,P<0.05）。对于OAR,与IPSA计划相比,HIPO计划中膀胱的D_{2 cm³}（3.42±0.17）Gy,直肠的D_{2 cm³}（3.04±0.37）Gy,明显低于IPSA计划膀胱的D_{2 cm³}（3.57±0.28）Gy,直肠的D_{2 cm³}（3.21±0.48）Gy,差异具有统计学意义（t=0.27、0.19,P<0.05）。乙状结肠D_{2 cm³}剂量两者差异无统计学意义。结论 在宫颈癌腔内联合组织间插植后装治疗中,采用HIPO优化比IPSA优化可以获得更好的靶区HI以及减少膀胱和直肠的受照剂量。     

Dosimetric comparison of multichannel with one single-channel vaginal cylinder for vaginal cancer treatments with high-dose-rate brachytherapy

PurposeTo compare the three-dimensional (3D) image (CT/MR)-based planning with a multichannel vaginal cylinder (MVC) to a single-channel vaginal cylinder (SVC) for the treatment of vaginal cancer.Methods and MaterialsA total of 20 consecutive patients were treated with 3D CT/MR image-based high-dose-rate (HDR) brachytherapy using an MVC. All patients received external beam radiation therapy before HDR brachytherapy. A brachytherapy dose of 20–25 Gy of more than five fractions was delivered to clinical target volume (CTV). Retrospectively, treatment plans for all patients were generated using the central channel only to mimic an SVC applicator. The SVC plans were optimized to match CTV coverage with MVC plans. Dose homogeneity index as well as bladder, rectum, sigmoid, and urethral doses were compared.ResultsThe mean D₉₀ for CTV was 74.2 Gy (range: 48.8–84.1 Gy). The mean (±standard deviation) of dose homogeneity index for MVC vs. SVC was 0.49 (±0.19) and 0.52 (±0.23), respectively (p = 0.09). Mean bladder 0.1, 1, and 2 cc doses for MVC vs. SVC were 69 vs. 71.2 Gy (p = 0.35), 61.4 vs. 63.8 Gy (p = 0.1), and 59.5 vs. 60.9 Gy (p = 0.31), respectively. Similarly, mean rectum 0.1, 1, and 2 cc doses for MVC vs. SVC were 67.2 vs. 75.4 Gy (p = 0.005), 60.0 vs. 65.6 Gy (p = 0.008), and 57.3 vs. 62.0 Gy (p = 0.015), respectively, and mean sigmoid doses were 56.3 vs. 60.5 Gy (p = 0.10), 50.9 vs. 53.1 Gy (p = 0.09), and 49.1 vs. 50.7 Gy (p = 0.10), respectively.ConclusionThe 3D CT-/MR-based plan with MVC may provide better dose distribution in the management of certain clinical situations of vaginal cancer requiring intracavitary brachytherapy, especially in minimizing potential late rectal complications.     

局部晚期宫颈癌腔内放疗联合组织间插植的剂量学研究

目的 比较局部晚期宫颈癌单纯腔内放疗与腔内联合组织间插植放疗的剂量学差异。方法 2016年5月—2017年3月局部晚期宫颈癌患者共35例,均行根治性放疗,治疗方法为外照射+腔内联合组织间插植放疗。调强放射治疗处方剂量为46.8~50.4 Gy/26~28次,1.8 Gy/次。腔内联合组织间插植放疗剂量为7 Gy/次,1次/周,共4次。同一患者首先置入三管式后装放疗施源器,采集CT图像制定治疗计划,取出三管式施源器后,置入宫腔管并植入插植针,再次采集图像制定放疗计划。分别评价比较两组计划中靶区及危及器官的受照剂量差别。结果 共制定212次后装放疗计划,其中单纯腔内治疗计划106例,腔内联合组织间插植治疗计划106例。腔内联合组织间插植放疗组计划较单纯腔内放疗组的靶区剂量明显升高,高危临床靶区（CTV）的D₉₀、中危CTV的D₉₀均显著增高（t=-6.01、-2.73,P<0.05）,膀胱、直肠、乙状结肠的D_{2 cm³}显著降低（t=3.07、4.52、2.91,P<0.05）。结论 局部晚期宫颈癌应用腔内联合插植放疗可以明显提高靶区剂量,并降低危及器官膀胱、直肠和乙状结肠的受照剂量。     

MRI-based interstitial brachytherapy for vaginal tumors: A multi-institutional study on practice patterns,contouring, and consensus definitions of target volumes

PurposeInterstitial brachytherapy (ISBT) can be effective for vaginal tumors due to its ability to deliver conformal treatment with 3D planning. As there is no consensus for 3D vaginal brachytherapy (BT) contouring, the goals of this study are to evaluate the variability in practices and contouring, and to develop consensus concepts on target definitions.MethodsA survey/contouring study was conducted with 16 radiation oncologists from 10 Canadian academic centers. The study included three vaginal ISBT cases. Participants were provided staging, prebrachytherapy (pre-BT), and BT MRIs. Participants responded to a questionnaire and contoured on the provided images. Agreement between contours was analyzed. A meeting was held to develop consensus definitions of targets.ResultsMedian ISBT experience was 3.5 years. All 16 participants regularly contour with MRI, whereas three also plan on MRI. For the three cases, there was variation into how CTV_HR and CTV_IR was defined. Kappa statistics showed higher agreement with bulky tumors (mean 0.59) as compared with small residual tumors (mean 0.29). For all cases, kappa was highest in pre-BT GTV_res as compared with BT GTV_res (mean 0.58, 0.46). Consensus concepts to define targets were developed.ConclusionsVariations exist in how ISBT targets are defined for vaginal tumors. Highest contouring variability was seen with small residual at BT. Contouring is more consistent on pre-BT MRI as compared with BT MRI suggesting a needle distortion effect. Consensus CTV_HR and CTV_IR definitions have been developed and further work is warranted to establish international standards.     

Dosimetric study of CO-60 source step size in uterine cervix intracavitary HDR brachytherapy

Purpose

The present work reports effects of source step sizes on dose distribution in patients treated with cobalt-60 (Co-60) high-dose-rate afterloading brachytherapy in carcinoma cervix (Ca-cx).

Development of an indigenous low-cost multichannel cylinder applicator for vaginal tumors

PurposeThe purpose of this study was to report our experience regarding the development of a low-cost multichannel vaginal cylinder applicator for superficial and recurrent vaginal tumors.Methods and MaterialsThe applicator mold was created by applying heated wax sheets in layers around a plastic tube. Interstitial stainless-steel needles were placed at equal distance around the mold surface to create multiple channels for treatment. Two plans were created using CT images for a patient with a recurrent tumor over the posterior vaginal wall for comparing single-channel and multichannel cylinder dosimetry. The doses received by the target (high risk clinical target volume) and organs at risk (OARs) were computed using dose–volume histograms.ResultsThere was no significant difference in terms of the prescribed dose delivered to high risk clinical target volume between the two plans. The volume of the target receiving 150 and 200 percent (V₁₅₀ and V₂₀₀) dose was higher in the multichannel cylinder plan than the single-channel cylinder plan. In terms of doses to the OARs, there was no significant difference between the rectum doses (D2cc rectum). There was a significant reduction in the dose to the bladder (D2cc bladder), urethra (D0.1cc urethra), and uninvolved vagina (D2cc uninvolved vagina).ConclusionsMultichannel vaginal cylinders reduce doses to the OARs as compared with the single-channel vaginal cylinder in superficial vaginal lesions limited to the wall of the vagina. Their use is limited by the cost of the applicator. Our low-cost multichannel vaginal cylinder can be used as a reliable alternative in such situations.     

Dosimetric consequences of seed placement accuracy in permanent breast seed implant brachytherapy

PurposeThis study quantifies the dosimetric impact of implant accuracy and derives a quantitative relationship relating implant accuracy to target dosimetry.Methods and MaterialsA framework was developed to simulate multiple implants for error combinations. Spherical clinical target volumes (CTVs) were modeled with volumes 1.4 cm³, 9.2 cm³, and 20.6 cm³, representing the range seen clinically. Each CTV was expanded 10 mm isotropically to create a planning target volume (PTV).. Random and systematic seed placement errors were simulated by shifting needles from their planned positions. Implant errors were simulated over the range of clinically practical errors in permanent breast seed implant. The relative effect on target coverage was evaluated. Regression analysis was performed to derive relationships between CTV dosimetry and the magnitude of implant accuracy. The validity of the clinically used 10 mm PTV margin for each of the CTVs was assessed.ResultsIntroducing practical implant errors resulted in CTV V_90% median (10th and 90th percentile) of 97.7% (85.9% and 100%), 96.2% (86.8% and 99.7%), and 100% (77.8% and 100%) for the typical, large, and small CTV, respectively. All CTVs show similar trends in target coverage. Polynomials were derived relating seed placement accuracy to median (R² = 0.82) and 10th percentile (R² = 0.78) CTV V_90%._.ConclusionsThis work quantitatively describes the relationship between implant accuracy and CTV coverage. Based on simulations, the 10 mm PTV margin is adequate to maintain target coverage. These equations can be used with institutional seed placement accuracy to estimate coverage.     

Evaluating adjacent organ radiation doses from postoperative intracavitary vaginal vault brachytherapy for endometrial cancer

PurposeTo document doses received by critical organs during adjuvant high-dose-rate (HDR) vaginal vault brachytherapy.Methods and MaterialsPatients treated with HDR vaginal vault radiation between January 1, 2009, and January 31, 2012, who had a CT simulation with the treatment cylinder in situ were included. The CT scans were retrospectively reviewed and the rectum, sigmoid, small bowel, and bladder were contoured. Standardized plans treating the upper 4 cm of the vaginal vault were used to deliver a total of 21 Gy (Gy) at 0.5 cm from the apex of the vaginal vault in three fractions.ResultsThere were 41 patients. Median age was 62 years. The median vaginal cylinder diameter was 3 cm. The mean 2cc dose to the rectum, sigmoid, small bowel, and bladder were 5.7, 4.7, 4.0, and 5.6 Gy, respectively. Bladder volume ranged from 67–797 cc. Assuming minimal interfraction organ variation, the equivalent dose in 2 Gy/fraction was extrapolated from data and may be near or beyond organ tolerance for rectum, sigmoid, and small bowel in some cases. Spearman correlation found that increased bladder volume was not associated with adjacent organs at risk dose but may be associated with a trend (p = 0.06) toward increased bladder dose (R = 0.30).ConclusionsThis study describes the dose received by adjacent critical structures during vaginal vault HDR brachytherapy. This is important information for documentation in the rare setting of treatment-related toxicity or recurrence. Bladder volume was not associated with dose to adjacent organs.     

Resident experience in brachytherapy: An analysis of Accreditation Council for Graduate Medical Education case logs for intracavitary and interstitial brachytherapy from 2007 to 2018

PurposeWe sought to characterize temporal trends of radiation oncology resident–reported case experience with intracavitary brachytherapy (ICBT) and interstitial brachytherapy (ISBT).Methods and MaterialsSummarized, deidentified case logs for graduating radiation oncology residents (GRORs) between 2007 and 2018 were obtained from the Accreditation Council for Graduate Medical Education national summary data report. Cases were subdivided based on the site of treatment. Analysis of variance was used to determine differences, and strength of association was evaluated using the Pearson correlation.ResultsThe number of GRORs increased by 66% from 114 in 2007 to 189 in 2018 (p < 0.001). Average number of gynecologic ICBT cases per GROR increased, from 39.6 in 2007 to 48.7 in 2018 (p < 0.005). Average number of ISBT cases per GROR decreased, from 34.5 to 20.6 (p < 0.001), due to decreasing prostate volume, from 21.5 to 12 (p < 0.001). Experience with gynecologic ISBT cases remained low at an average of 4.5 cases per year.ConclusionsThe average number of ICBT cases per GROR has increased, although this does not differentiate between cylinder and tandem-based insertions currently. There has been a steady decline in ISBT experience. These findings may have implications for the development of Accreditation Council for Graduate Medical Education case minimums for residency programs.     

Three-dimensional treatment planning for vaginal cuff brachytherapy: Dosimetric effects on organs at risk according to patients position

PurposeAim of this study was to evaluate dose distribution within organs at risk (OARs) and planning target volume (PTV) based on three-dimensional treatment planning according to two different setup positions in endometrial carcinoma patients submitted to postoperative brachy-radiotherapy on vaginal vault.Methods and MaterialsPatients with endometrial cancer necessitating of adjuvant brachytherapy on vaginal vault were enrolled. Pelvic computed tomography studies were prospectively obtained in two different setup positions: extend legs (A position) and gynecological (B position). Contoured OARs were bladder, rectum, and small bowel. The PTV was identified as applicator's surface with an isotropic 5-mm margin expansion. Radiation dose delivered in 1 cc (D_1cc) and 2 cc (D_2cc) of OAR were calculated.ResultsCoverage of PTV and values of D_1cc and D_2cc obtained for bladder and small bowel were similar in the two positions. For rectum, both D_1cc and D_2cc had statistically significant lower values in A with respect to B position.ConclusionsBoth in A and B positions, radiation doses delivered do not exceed the dose constraints. However, A setup seems to significantly reduce doses to rectum while obtaining the same PTV coverage. The findings from our study provide evidence supporting the use of A position setup for delivering vaginal vault brachytherapy.     

A modified technique for high-dose-rate intracavitary brachytherapy in advanced cancer of the cervix

PURPOSE: To develop a modified technique for high-dose-rate intracavitary brachytherapy in cervical cancer stage IIIb. METHODS AND MATERIALS: Cervical carcinoma FIGO Stage III accounts for > 60% of all cervical cancers with radiation being the mainstay of treatment for most patients. After external beam radiation therapy (EBRT), the cervix is often flush with the vagina and the shape of the vagina may be conical with its apex at the external os level. All patients receive 2 applications with HDR brachytherapy. At the first application after the placement of the central tandem, only one ovoid is inserted and the other ovoid is replaced by a rubber tube, and the applicator assembly is fixed as usual. The contralateral ovoid is inserted at the subsequent application. RESULTS: To date, 21 locally advanced cervical cancer patients have been treated using this technique. In these patients, the mean dose to right and left Point A was 93% (range, 86-100%; median, 93%) and 95% (range, 90-100%; median, 95%), respectively. The variation of doses to the contralateral Point A was 1-14%. The mean dose to the rectal and bladder mucosa was 62% (range, 43-80%; median, 64%) and 80% (range, 50-110%; median, 71%), respectively. CONCLUSION: This modified HDR intracavitary technique may prove an alternative for centers where interstitial brachytherapy for cancer of the cervix is not available.     

Individual fraction optimization vs. first fraction optimization for multichannel applicator vaginal cuff high-dose-rate brachytherapy

PURPOSE: To challenge the assumption of unchanged interfractional geometry changes in the course of fractionated multichannel vaginal cuff high-dose-rate brachytherapy. METHODS AND MATERIALS: Two methods of treatment planning for delivery of vaginal cuff brachytherapy were compared in 44 applications. Individual fraction optimization (IFO)-performed for the specific geometry of each individual fraction-was compared to first fraction optimization (FFO)-an optimized first fraction, applied unaltered for geometry of subsequent fractions in the same patient. Dose difference to critical organs was expressed as the percentage of the prescribed dose. RESULTS: In the paired analysis for IFO vs. FFO, mean and maximum rectal and bladder doses were similar. However for FFO, an excess of greater than 20% mean dose to either bladder or rectum was observed in 41% of cases. Maximum organ doses were exceeded by 20% in 54.5% of applications. CONCLUSIONS: On the basis of these findings, it can be concluded that IFO may be important to minimize doses to critical structures.     

Dose distribution of brachytherapy for locally advanced (stage IIB) cervical cancer

PurposeThe aim of the study was to compare the dose distributions of combined intracavitary and interstitial (IC/IS) brachytherapy with 3-catheter IC brachytherapy in treating locally advanced (stage IIB) cervical cancer.Methods and MaterialsIn total, 46 patients were included, each with stage IIB cervical cancer, local lesion sizes ≥5 cm, and tumors that had not regressed after 45 Gy/25 F external intensity-modulated radiotherapy. To identify the dosimetric advantage of delivering a local boost to high-risk (HR)-cervix in IC/IS, patients were divided into two groups: IC/IS and IC/IS + HR-cervix. The differences in dosimetric parameters were compared between the two groups. Comparisons were then made between the parameters of the four planning methods: IC (Point A), IC (three dimensional [3D]), IC/IS, and IC/IS + HR-cervix.ResultsIn patients with IC/IS implants, the relative uterine tandem dwell time was significantly extended in the IC/IS + HR-cervix group, and the V150 and V200 volumes of HR-cervix were increased (all p < 0.001), whereas the D90 and D100 values of the IC/IS + HR-cervix group were lower than those in the IC/IS group. In pairwise comparisons, HR-cervix V150 and V200 values were lowest in the IC/IS group, followed by the IC (3D), IC/IS + HR-cervix, and IC (Point A) groups. All differences were statistically significant (p < 0.05), with the exception of IC/IS vs. IC (3D).ConclusionsWhen treating locally advanced cervical cancer (stage IIB, local residual volume ≥5 cm after external radiotherapy), the IC/IS + HR-cervix optimization method can meet the HR clinical target volume D90 dose requirement, normal tissue dose limits, and can escalate doses to local areas of the cervix.     

介入化疗加后装放射治疗复发性鼻咽癌的近期疗效观察

目的 探讨介入化疗辅加后装放射治疗复发性鼻咽癌的临床疗效。方法 32例复发性鼻咽癌分为：16例介入化疗辅加后装放射治疗组，介入化疗术后第3天作首次后装放射治疗，4d后行第2次后装放射治疗。16例单纯行后装放射治疗。剂量及2次间隔时间2组相同，每次5GY。复查时间统一在后装放疗后2周。结果 介入化疗辅加后装放射治疗组，临床症状改善明显，局部肿大淋巴结明显缩小，鼻咽部肿瘤表面分泌滞留极少或消失，肿瘤明显缩小，并呈干枯或萎缩样变；单纯后装放射治疗组，临床症状改善不明显，除鼻咽部肿瘤表面分泌物较治疗前有所减少外，局部肿大淋巴，鼻咽部肿瘤红肿充血与放疗前无明显改变。介入组未见有肝肾功能损害及明显术后消化道反应。结论 介入化疗辅加后装内照射治疗复发性鼻咽癌具有双重直接局部杀伤杀死肿瘤细胞作用，是治疗复发性鼻咽癌的一种新的治疗途径。     

乌德勒支施源器用于局部晚期宫颈癌三维近距离放疗的剂量学研究

目的 探讨在使用乌德勒支施源器治疗局部晚期宫颈癌时,不同的管道组合设计与靶区、危及器官（OAR）的剂量关系。方法 调取2017—2018年于河北省沧州中西医结合医院放疗科接受乌德勒支施源器进行近距离治疗的17例局部晚期宫颈癌患者数据,原计划为腔内联合组织间插植近距离放疗（IC/IS）,在原勾画轮廓与照射剂量不变的情况下,去除插植针完成腔内近距离放疗（IC）计划设计,对IC/IS计划和IC计划的剂量参数进行对比分析,并评价加入IS插植针对剂量的影响。结果 IC/IS和IC计划的高危临床靶区（HR-CTV）总的D₉₀分别（88.68±1.84）和（85.54±0.54）Gy,差异具有统计学意义（t=6.200,P<0.05）。此外,在靶区的CI指数上,IC/IS计划的明显高于IC计划（0.58±0.08,0.43±0.05）,差异具有统计学意义（t=1.010,P<0.05）。在两种计划中危及器官（OAR）的受照剂量差异无统计学意义（P>0.05）。结论 对于局部晚期宫颈癌的近距离治疗,使用乌德勒支施源器可满足其处方剂量覆盖,而加入IS针,提高了计划的优化空间,在满足OAR受照剂量限值的基础上,显著提高HR-CTV的受照剂量,且提升了剂量分布均匀性。