Late rectal toxicity after image-based high-dose-rate interstitial brachytherapy for postoperative recurrent and/or residual cervical cancers: EQD2 predictors for Grade ≥II toxicity

Dosimetric predictors of local control and complications in gynecologic transperineal implant patients: The medical college of wisconsin experience

PURPOSE

Investigate the relationship between dosimetric parameters with local control (LC) and complications following transperineal high-dose rate (HDR) interstitial brachytherapy (ISBT) for gynecologic (GYN) malignancies.

METHODS AND MATERIALS

Between 2001 and 2016, 59 patients were treated for primary or recurrent GYN malignancies. Most patients received external beam irradiation, followed by transperineal ISBT via the Syed-Neblett applicator set with CT-based planning. Treatment plans were retrospectively reviewed to evaluate for an association among LC or toxicity with the equivalent dose at 2 Gy per fraction (EQD2) for the clinical target volume (CTV), 0.1 cc (D0.1cc), and 2 cc (D2cc) volumes of the organs at risk (OAR), low/high dose volumes for the OAR and CTV, and ratio of dose at the core vs. the implant periphery.

RESULTS

The median follow-up among survivors was 24 months. 34% of patients had a component of local failure and in 12%, this was isolated. Late grade 3 (G3) toxicity occurred in 15% of patients. There were no G4-5 toxicities. Rectal D0.1cc > 75 Gy trended toward significance in predicting the development of non-fistula late G2-3 rectal complications. Bladder D0.1cc > 94 Gy significantly predicted for the development of late G2-3 vesicovaginal fistula formation. The ratio of the total dose at the vaginal surface to the needle periphery above 121% trended in predicting for any complication or fistula formation.

CONCLUSIONS

HDR ISBT combined with EBRT achieved LC in 66% of patients with advanced or recurrent GYN cancers. Rectal and bladder D0.1cc doses may be predictive of complications as may the ratio of the implant dose at the core vs. periphery.

Morbidity following image-guided brachytherapy for cervical cancer: Patient and treatment related factors

PURPOSE

This retrospective study aims to assess factors associated with the occurrence of toxicity after brachytherapy (BT), as boost after external beam radiotherapy (EBRT) for treatment of invasive cervix carcinoma.

METHODS AND MATERIALS

All consecutive patients diagnosed with cervical carcinoma, and treated with concurrent radiochemotherapy from August 2017 to January 2020 were retrospectively included. An isodose conformation index (ICI) was developed to assess the percentage of the prescription isodose contained within the intermediate risk clinical target volume (IR-CTV).

RESULTS

Eighty-one patients with invasive cervix carcinoma from stage IB to stage IVa were included. Thirty-two (40%) and 49 (60%) patients were treated with Pulsed Dose Rate (PDR) and High Dose Rate (HDR) BT, respectively. Median follow-up was 19.6 months (5.6-41.2). The main factors associated with development of gastrointestinal toxicity were: the median volume of the prescription isodose (67.9cm[3] [37.6-92.9] vs. 49.1cm[3] [34.5-53.5], p = 0.05), the value of ICI (59% [51%-83%] vs. 86% [65%-96%], p = 0.01), the median equivalent dose delivered to the sigmoid (D2cc= 58.4 GyEQD2 [53.9-61.1] vs. 55.2 GyEQD2 [52.8-57.5], p = 0.06) and the median equivalent dose delivered to the IR-CTV (D90= 63.9 GyEQD2 [60.6-66.4] vs. 61.2 GyEQD2 [59.4-64.5], p = 0.03). The proportion of patients who received EBRT lymph node boost was higher in patients who developed urinary toxicity than in patients who did not (57.1% vs. 28.6%, p = 0.08). Anticoagulant (p = 0.02) and antiaggregant therapy (p = 0.01) were associated with occurrence of both urinary and gastrointestinal toxicity.

CONCLUSIONS

Our study confirms the predictive value of irradiated volume in the occurrence of gastrointestinal toxicity, as well as the need for a better conformation to the target volume. Precautions should be considered in patients with vascular comorbidities.

The Relationship Between Late Morbidity and Dose-Volume Parameter of Rectum in Combined Intracavitary/Interstitial Cervix Cancer Brachytherapy: A Mono-Institutional Experience

Purpose

To establish a dose volume–effect relationship for predicting late rectal complication (LRC) in locally advanced cervical cancer patients treated with external beam radiotherapy (EBRT) followed by combined intracavitary/interstitial brachytherapy (IC/IS-BT).

Materials and Methods

A retrospective analysis was performed in 110 patients with locally advanced cervical cancer who underwent definitive radiotherapy combined with IC/IS-BT from July 2010 to September 2018. We report the 90% of the target volume receiving the minimum dose for high risk clinical target volume (HR-CTV D₉₀) and intermediate risk clinical target volume (IR-CTV D₉₀), and the minimum doses to the most exposed 0.1, 1, and 2 cm³ D0.1cm3,D1cm3,D2cm3 doses at the International Commission on Radiation Units and Measurements (D_ICRU) for organs at risk (OARs). The total dose of EBRT plus brachytherapy was transformed to the biologically equivalent dose in 2 Gy fractions (EQD2) with α/β value of 10 Gy for target, 3 Gy for organs at risk using the linear quadratic model. The morbidity was scored according to the Radiation Therapy Oncology Group (RTOG) criteria. The Probit model was used to establish a prediction model on rectum between the organs at risk for dose and LRC. The receiver operating characteristic (ROC) curve was used to evaluate the predictive value of dose volume parameters for LRC.

Results

The median follow-up time was 72.3 months. The mean ( ± standard deviation) D2cm3,D1cm3,D0.1cm3, and D_ICRU values of rectum were 64.72 ± 7.47 Gy_EQD2, 70.18 ± 5.92 Gy_EQD2, 79.32 ± 7.86 Gy_EQD2, and 67.22 ± 7.87 Gy_EQD2, respectively. The Probit model showed significant relationships between D1cm3 or D0.1cm3, and the probability of grade1–4, grade 2–4 rectal events at 1 year, and between D1cm3and the probability of grade2–4 rectal events at 3 and 5 years. The dose values for 10% complication rates (ED10) of D1cm3were 74.18 (70.42–76.71) Gy_EQD2, 67.80 (59.91, 71.08) Gy_EQD2, 66.37 (52.00, 70.27) Gy_EQD2 for grade 2–4 with rectal morbidity at 1, 3, and 5 years, respectively.

Conclusion

Our study proved that D1cm3 andD0.1cm3were considered as useful dosimetric parameters for predicting the risk of grade1–4 and grade2–4 LRC at 1-year, and D1cm3might be an indicator for predicting grade2-4 LRC at 3/5years. The patients with rectal D1cm3>66.37–74.18 Gy_EQD2 should be closely observed for grade2–4 LRC.

Interstitial brachytherapy for gynecologic malignancies: Complications, toxicities, and management

From both a disease and management perspective, locally advanced gynecologic cancers present a significant challenge. Dose escalation with brachytherapy serves as a key treatment, providing conformal radiation while sparing at-risk organs. Intracavitary brachytherapy techniques have been shown to be effective, with improving tumor control and toxicity profiles with the advent of three-dimensional image planning. Despite this, the variations in tumor size, location, and pelvic anatomy may lead to suboptimal dosimetry with standard intracavitary applicators in some clinical scenarios. The addition of interstitial needles (interstitial brachytherapy (ISBT)) can improve the conformality of brachytherapy treatments by adding needles to peripheral (and central) regions of the target volume, improving the ability to escalate doses in these undercovered regions while sparing organs at risk. Interstitial brachytherapy can be delivered by intracavitary and interstitial hybrid applicators (ICBT/ISBT), perineal template (P-ISBT), or by free-hand technique. ISBT has however yet to be widely available because of concerns of complications and toxicities from this specialized treatment. However, with the increasing use of three-dimensional image-guided brachytherapy, there is an opportunity to increase the level of expertise in the gynecologic radiation oncology community with an improved understanding of the potential complications and morbidity. In this article, we review the acute and long-term toxicity in both ICBT/ISBT and P-ISBT using image-guided brachytherapy.

Analysis of Radiation Dose/Volume Effect Relationship for Anorectal Morbidity in Children Treated for Pelvic Malignancies

PURPOSE

To examine dose-volume effect relationships for anorectal morbidity in children treated with image-guided brachytherapy for pelvic tumors.

METHODS AND MATERIALS

Medical records of all consecutive children with pelvic tumors treated in our center and receiving image-guided pulsed-dose-rate brachytherapy with or without external beam radiation therapy (EBRT) between 2005 and 2019 were reviewed. The effect of the minimal doses to the most exposed 0.5 cm³, 1 cm³, and 2 cm³ of the anorectum (respectively: D_0.5cm³, D_1cm³, and D_2cm³), total reference air kerma (TRAK), and volume of 100% isodose was examined for anorectal toxicities.

RESULTS

Seventy-eight consecutive children were included. Median age was 2.9 years (range, 0.8-14.9 years). Most of the tumors were bladder or prostate (67%) or vaginal (22%) rhabdomyosarcoma. Six patients received EBRT in addition to brachytherapy. Median follow-up was 21.3 months. At last follow-up, 30 children (38%) had experienced Common Terminology Criteria for Adverse Events version 5 grade ≥1 acute or late anorectal events: 24% had grade 1 events, 7.7% had grade 2 events, and 6.4% had grade 3 events. No toxicity greater than grade 3 was observed (eg, fistula or stricture). In univariate analysis, the D_0.5cm³ and D_1cm³ were significant for probability of grade 1 to 3 (P = .009 and P = .017, respectively) and grade 2 to 3 anorectal morbidity (P = .007 and P = .049, respectively). There was no significant correlation for D_2cm³ (P = .057 for grade 1-3; P = .407 for grade 2-3). A 10% probability (95% confidence interval, 4%-20%) for anorectal toxicity of grade 2 or greater was reached for a D_0.5cm³ = 52 Gy. The age, EBRT use, TRAK, and treated volume values were not significant.

CONCLUSIONS

To our knowledge, this study is the first to show a significant dose-volume effect relationships for anorectal morbidity in children undergoing treatment with brachytherapy. Integrating these data into brachytherapy treatment planning could help to optimize the therapeutic index in these young patients.

Brachytherapy in India: Learning from the past and looking into the future

India has a longstanding tradition in the practice of brachytherapy and has actively contributed to the scientific literature by conducting prospective studies, clinical audits, developing innovative techniques, and performing randomized studies. Indian investigators have also contributed to international collaborative research, education, training programs along with guideline development for brachytherapy in cervix and head and neck cancers. The present article summarizes the key contributions to scientific literature, current infrastructure, skill set for brachytherapy, existing challenges, and strategy to further strengthen brachytherapy practice in the next decade.

Analysis of clinical utilization of ring applicator for combined intracavitary/interstitial image-guided brachytherapy treatment in Chinese patients with locally advanced cervical cancer

Purpose

To analyze the results of clinical utilization of ring applicator for combined intracavitary (IC)/interstitial (IS) image-guided brachytherapy (BT) technique in locally advanced cervical cancer (LACC), and to explore the application conditions of IC/IS BT approach with this applicator for Chinese patients.

Material and methods

IC/IS BT was performed in total of 95 LACC patients, who already received external beam radiotherapy. In forty-three of these patients, utilization of ring applicator in brachytherapy was done, including IC/IS BT approach with ring applicator for 65 fractions. Clinically optimized IC/IS BT plan with ring applicator (IC/IS treatment) and additionally generated optimized plan without needle use (IC research) were designed, respectively. Dosage differences in target regions and organs at risk (OARs) were analyzed between both the plans. Four planes were selected in the longitudinal direction of uterine cervix and divided the 360° area around the tandem into eight equal sectors. Tumor target features and prescription dose distributions on different planes were described.

Results

The usage rate of ring applicator with most suitable ring diameter of 26 mm was 45.3% in Chinese cervical cancer patients. The high-risk clinical target volume (HR-CTV) D₉₀/D₉₈ and intermediate-risk CTV (IR-CTV) D₉₀/D₉₈ in IC/IS treatment were significantly higher than IC research. As compared with IC research plan, the D_{2.0 cm³} of bladder and rectum in IC/IS treatment were significantly lower (p < 0.05). There was no significant difference in D_{2.0 cm³} of sigmoid and small bowel between two plans. When the target volume was larger than 36 cm³, IC alone had an inadequate coverage of target.

Conclusions

Nearly half of Chinese patients with LACC could be treated with the ring applicator. The application conditions of IC/IS BT approach with ring applicator for Chinese patients were achieved. Combined IC/IS image-guided BT based on magnetic resonance imaging (MRI) planning is clinically feasible in Chinese patients.

Hyaluronic acid gel injection in rectovaginal septum reduced incidence of rectal bleeding in brachytherapy for gynecological malignancies

PURPOSE

The purpose of this study was to report our initial clinical results of hyaluronic acid gel injection (HGI) in the rectovaginal septum (RVS) to reduce the incidence of rectal bleeding in vaginal brachytherapy for gynecologic malignancies.

METHODS AND MATERIALS

Since 2008, CT based image-guided adaptive brachytherapy (IGABT) was initiated, and since 2015, HGI in the RVS was introduced in our institution. Vaginal cylinder with or without tandem or additional interstitial needles were applied for patients with gynecologic malignancies. Rectum dosimetric parameters and incidence of late rectum bleeding were compared between patients with and without HGI in the RVS.

RESULTS

Between May 2008 and October 2017, 83 patients with gynecologic malignancies were treated with IGABT involving vaginal cylinder. Eleven patients who were treated for palliative intention were excluded, and 72 patients were subjected to the analysis. Of the total 72 patients 46 were with uterine cervical cancer, 19 uterine corpus cancer, five vaginal cancer, one vulvar cancer, and one ovarian cancer. Fifteen and 57 patients were irradiated with and without HGI in the RVS, respectively. With a median follow-up period of 57.7 (4.7-123.1) months, 30 (41.7%) patients suffered from radiation-related rectal bleeding. Patients with HGI in the RVS had a statistically significant lower incidence of rectal bleeding compared with those without it (13.3% vs. 49.1%, p = 0.01).

CONCLUSIONS

HGI in the RVS reduced the incidence of late rectal bleeding for patients with gynecologic malignancies treated by vaginal cylinder and was not associated with HGI-procedure-related adverse events.

Increased risk for second primary rectal cancer after pelvic radiation therapy

BACKGROUND

The aim of this study was to analyse the association between pelvic radiation therapy (RT) and the development of rectal cancer as a second primary cancer.

METHODS

Data on patients treated for a primary pelvic cancer between 1989 and 2007 were retrieved from the population-based Netherlands Cancer Registry. Patients treated for more than one pelvic cancer were excluded. To estimate the cumulative incidence of rectal cancer, Fine and Gray's competing risk model was used with death as a competing event. Survival was calculated using multivariable Cox regression.

RESULTS

A total of 192,658 patients were included, of which 62,630 patients were treated with RT for their pelvic cancer. Primary tumours were located in the prostate (50.1%), bladder (19.2%), endometrium (13.9%), ovaries (10.0%), cervix (6.4%) and vagina (0.4%). At a median interval of 6 years (range 0-24), 1369 patients developed a rectal cancer. Overall, the risk for rectal cancer was increased in patients who underwent RT for the previous pelvic cancer (subhazard ratio [SHR]: 1.72, 95% confidence interval [CI]: 1.55-1.91). Analysis for each tumour location specifically showed an increased risk in patients who received RT for prostate (SHR: 1.89, 95% CI: 1.66-2.16) or endometrial cancer (SHR: 1.50, 95% CI: 1.13-2.00). A protective effect of RT was observed for patients with bladder cancer (SHR 0.67, 95% CI: 0.47-0.94). There was no survival difference between patients with rectal cancer with or without previous RT (hazard ratio: 0.94, 95% CI: 0.79-1.11).

CONCLUSIONS

Patients who received RT for a previous pelvic cancer were at increased risk for rectal cancer. The risk was modest and pronounced in patients receiving RT for prostate and endometrial cancer.

MRI- and PET-Guided Interstitial Brachytherapy for Postsurgical Vaginal Recurrences of Cervical Cancer: Results of Phase II Study

PURPOSE

This phase II study evaluated the utility of magnetic resonance imaging (MRI) and positron emission tomography for planning radiation and brachytherapy in patients with postsurgical recurrence of cervical cancer.

METHODS AND MATERIALS

The study (NCT01391065) recruited patients with residual or recurrent disease after hysterectomy. Patients underwent baseline T2 weighted (T2W) MRI, ¹⁸F-flouro-deoxyglucose (¹⁸F-FDG), ¹⁸F-flouro thymidine (¹⁸F-FLT) and ¹⁸F-flouromisonidazole (¹⁸F-F Miso) positron emission tomography (PET) and received external radiation (50 Gy/25 fractions for 5 weeks) and weekly cisplatin (40 mg/m²). MRI was performed at brachytherapy and used for delineation of clinical target volume (CTV). Patients with parametrial disease at baseline received interstitial brachytherapy (16-20 Gy/4-5 fractions) and those with vaginal disease received intracavitary brachytherapy (12-14 Gy/2-4 fractions). Kaplan-Meier analysis was performed to evaluate locoregional relapse, disease free survival, and overall survival. Common Toxicity Criteria for adverse event reporting (CTCAE) v4.1 was used for toxicity scoring and European Organization for Research and Treatment of Cancer (EORTC) Quality of Life Questtionaire Core 30 (QLQC-30) and Cx 24 for quality-of-life reporting.

RESULTS

Between January 2011 and February 2016, 60 patients were included, of which 50 received study treatment. The mean gross tumor volume on T2 W MR was 20 (IQR 3.6-90) cc. The metabolic tumor volume was 15 (interquartile range [IQR] 2.1-56.1) cc. The median FLT volume was 10 (IQR 0-48) cc. A total of 8 patients had ^18-F F Miso uptake. The median CTV at brachytherapy was 38 (12-85) cc. The median CTVD90 and D 98 was 71 (53-74) and 74 (53-74) Gy. At a median follow-up of 60 (5-93) months, the 5-year local control, disease free survival, and overall survival were 84%, 73%, and 74.5%, respectively. Grade III and IV proctitis and cystitis were observed in 4% and 2% of patients. On multivariate analysis baseline tumor volume, on T2 W MR impacted disease free (91% vs 65%, P = .03) and overall survival (96% vs 77%, P = .06).

CONCLUSIONS

Image-guided assisted radiation and brachytherapy are associated with good to excellent local control and survival in patients with vaginal recurrences of cervical cancer.

Initial experience using superflab as intravaginal packing during interstitial brachytherapy for advanced gynecologic cancer

Purpose

Interstitial brachytherapy implemented for locally advanced gynecologic cancer can result in toxicity due to the proximity of organs at risk (OAR). We report our experience using superflab bolus as vaginal packing to displace OAR during interstitial brachytherapy.

Material and methods

Twelve patients with stage IB-IVA gynecologic cancer were treated with definitive chemoradiation including interstitial brachytherapy. A Syed template was used for a computed tomography (CT)-based pre-plan with magnetic resonance imaging (MRI) fusion. A 1-2 cm superflab bolus was cut and sterilized. The tandem and obturator were placed, and superflab was then inserted into the vagina. Interstitial needles were then placed through the template and superflab as per the pre-plan under transabdominal ultrasound guidance. Prescription doses ranged from 85-90 Gy EQD₂ including external beam radiation therapy (EBRT). 5-6 Gy per fraction was delivered biologically effective dose (BID) over 2-3 days in 1-2 implants. Toxicities were evaluated post-treatment, 1 month, and 3 months.

Results

The rectum, bladder, and sigmoid had significant average displacement from the prescription isodose line. The average reduction in D_2cc between pre- and post-implant was 5.19 Gy per fraction (p < 0.0001), 7.19 Gy (p < 0.0004), and 1.78 Gy (p < 0.003) for the rectum, bladder, and sigmoid, respectively. The high-risk target volume (HR-TV) received a median D₉₀ of 104% (range, 58-122%) of the prescription dose, and 92% (range, 71-131%) in the pre-/post-implant plans, respectively (p = 0.4).

Conclusions

Our initial experience with superflab as vaginal packing demonstrates technical feasibility and dosimetric improvement for OAR.

The EMBRACE II study: The outcome and prospect of two decades of evolution within the GEC-ESTRO GYN working group and the EMBRACE studies

The publication of the GEC-ESTRO recommendations one decade ago was a significant step forward for reaching international consensus on adaptive target definition and dose reporting in image guided adaptive brachytherapy (IGABT) in locally advanced cervical cancer. Since then, IGABT has been spreading, particularly in Europe, North America and Asia, and the guidelines have proved their broad acceptance and applicability in clinical practice. However, a unified approach to volume contouring and reporting does not imply a unified administration of treatment, and currently both external beam radiotherapy (EBRT) and IGABT are delivered using a large variety of techniques and prescription/fractionation schedules. With IGABT, local control is excellent in limited and well-responding tumours. The major challenges are currently loco-regional control in advanced tumours, treatment-related morbidity, and distant metastatic disease. Emerging evidence from the RetroEMBRACE and EMBRACE I studies has demonstrated that clinical outcome is related to dose prescription and technique. The next logical step is to demonstrate excellent clinical outcome with the most advanced EBRT and brachytherapy techniques based on an evidence-based prospective dose and volume prescription protocol. The EMBRACE II study is an interventional and observational multicentre study which aims to benchmark a high level of local, nodal and systemic control while limiting morbidity, using state of the art treatment including an advanced target volume selection and contouring protocol for EBRT and brachytherapy, a multi-parametric brachytherapy dose prescription protocol (clinical validation of dose constraints), and use of advanced EBRT (IMRT and IGRT) and brachytherapy (IC/IS) techniques (clinical validation). The study also incorporates translational research including imaging and tissue biomarkers.

American Brachytherapy Society recurrent carcinoma of the endometrium task force patterns of care and review of the literature

PURPOSE

The purpose of this American Brachytherapy Society task force is to present a literature review and patterns of care by a panel of experts for the management of vaginal recurrence of endometrial cancer.

METHODS AND MATERIALS

In 2016, the American Brachytherapy Society Board selected a panel of experts in gynecologic brachytherapy to update our current state of knowledge for managing vaginal recurrence of endometrial cancer. Practice patterns were evaluated via an online survey and clinical updates occurred through a combination of literature review and clinical experience and/or expertise.

RESULTS

There are various retrospective series of patients treated with radiation for vaginal recurrence of endometrial cancer, which include a varied group of patients, multiple treatment techniques, and a range of total doses and demonstrate a wide scope of local control and overall survival outcomes. In the era of image-guided brachytherapy, high local control rates with low significant late-term morbidities can be achieved. Lower rates of local control and higher late-term toxicity are reported in the retreatment setting. In patients with no previous history of radiation treatment, external beam radiation therapy followed by brachytherapy boost should be used. There are varying practices with regard to the definition and appropriate doses of both the high-risk clinical target volume and the intermediate-risk clinical target volume in the setting of vaginal recurrence of endometrial cancer. There are limited data to provide appropriate dose constraints for some organs at risk with the majority of guidance taken from the definitive cervical cancer literature.

CONCLUSIONS

A summary of literature and expert practice patterns for patient selection, dose recommendations, and constraints are provided as guidance for practitioners.

Intermediate dose-volume parameters and the development of late rectal toxicity after MRI-guided brachytherapy for locally advanced cervix cancer

PURPOSE

The dose delivered to the most exposed 2 cm³ [Formula: see text] of the rectum and bladder is predictive of late rectal and bladder toxicity in cervix cancer patients. We investigated the predictive value of intermediate doses to the rectum and bladder for late rectal/bladder toxicity after MRI-guided brachytherapy for patients with locally advanced cervix cancer.

METHODS AND MATERIALS

Toxicity was prospectively graded using Common Toxicity Criteria for Adverse Events v4.0 and retrospectively verified for women with Stage IB-IVA cervix cancer treated consecutively with MRI-guided brachytherapy between 2008 and 2013. The minimum equivalent dose in 2 Gy fractions delivered to 0.1, 1, 2, 5, and 10 cm³ of the rectum and bladder and the absolute volume of the rectum receiving 55, 60, 65, 70, and 75 Gy₃ (V_55-75) were collected. The association between dose-volume parameters and Grade 2+ rectal/bladder toxicity was examined using logistic regression.

RESULTS

With a median followup of 44 months, cumulative incidences of Grade 2+ rectal and bladder toxicity among the 106 patients were 29% and 15% at 3 years, respectively. All the dose-volume parameters were significantly associated with late Grade 2+ rectal and bladder toxicity (p < 0.05), except for bladder [Formula: see text] . On multivariable logistic regression, both [Formula: see text]  > 70 Gy₃ and V₅₅ > 11 cm³ (p < 0.05) were predictive of late Grade 2+ rectal toxicity, with improved model fitting and higher area under the curve compared with the model with [Formula: see text]  > 70 Gy₃ alone.

CONCLUSIONS

In this study, V₅₅ was predictive of late Grade 2+ rectal toxicity. Adding V₅₅ to  [Formula: see text] improved prediction accuracy.

Effects of vaginal cylinder position on dose distribution in patients with endometrial carcinoma in treatment of vaginal cuff brachytherapy

PURPOSE

To investigate the impact of different cylinder positions on dosimetry of critical structures in patients with endometrial carcinoma undergoing three-dimensional image-based vaginal cuff brachytherapy (VCB).

MATERIAL AND METHODS

We delivered VCB at a dose of 4 Gy to a depth of 5 mm in the vaginal cuff of 15 patients using three different cylinder positions (neutral [N], parallel [P], and angled [A]) according to the longitudinal axis of the patient. We analyzed the dose-volume distribution and volumetric variability of the rectum and bladder. We converted the total doses to equivalent doses in 2 Gy (EQD₂) using a linear-quadratic model (a/b = 3 Gy).

RESULTS

The mean rectum volume for the N, P, and A positions was 68.2 ± 22.7 cc, 79.3 ± 33.7 cc, and 74.2 ± 29.6 cc, respectively. The mean rectum volume for the P position was significantly larger than that for the N position (p = 0.03). Relative to the N position, the A position resulted in a lower total EQD₂ in the highest irradiated 2 cc (D_2cc; p = 0.001), 1 cc (D_1cc; p = 0.004), and 0.1 cc (D_0.1cc; p = 0.047) of the rectum. Similarly, the P position resulted in a lower EQD₂ in the D_2cc (p = 0.018) and D_1cc (p = 0.024) of the rectum relative to the N position. In the bladder, the P position resulted in a higher EQD₂ in the D_2cc relative to the N position (p = 0.02). There was no dosimetric difference between the P and A positions in either the rectum or the bladder.

CONCLUSIONS

Vaginal cuff brachytherapy in the P and A positions is significantly superior to that in the N position in terms of rectum dosimetry. The bladder dose in the N position is considerably lower than that in the other positions.

Dose-volume effect relationships for late rectal morbidity in patients treated with chemoradiation and MRI-guided adaptive brachytherapy for locally advanced cervical cancer: Results from the prospective multicenter EMBRACE study

PURPOSE

To establish dose volume-effect relationships predicting late rectal morbidity in cervix cancer patients treated with concomitant chemoradiation and MRI-guided adaptive brachytherapy (IBABT) within the prospective EMBRACE study.

MATERIAL AND METHOD

All patients were treated with curative intent according to institutional protocols with chemoradiation and IGABT. Reporting followed the GEC-ESTRO recommendations ( [Formula: see text] , [Formula: see text] ), applying bioeffect modeling (linear quadratic model) with equieffective doses (EQD2₃). Morbidity was scored according to the CTC-AE 3.0. Dose-effect relationships were assessed using comparisons of mean doses, the probit model and log rank tests on event-free periods.

RESULTS

960 patients were included. The median follow-up was 25.4months. Twenty point one percent of the patients had grade 1 events, 6.0% grade 2, 1.6% grade 3 and 0.1%, grade 4. The mean D_ICRU, [Formula: see text] , and [Formula: see text] were respectively: 66.2±9.1Gy, 72.9±11.9Gy, and 62.8±7.6Gy. Increase of dose was associated with increase in severity of single endpoints and overall rectal morbidity (grade 1-4) (p<0.001-0.026), except for stenosis (p=0.24-0.31). The probit model showed significant relationships between the [Formula: see text] , [Formula: see text] , and D_ICRU and the probability of grade 1-4, 2-4, and 3-4 rectal events. The equieffective [Formula: see text] for a 10% probability for overall rectal grade⩾2 morbidity was 69.5Gy (p<0.0001). After sorting patients according to 6 [Formula: see text] levels, less favorable outcome was observed in the high dose subgroups, for bleeding, proctitis, fistula, and overall rectal morbidity. A [Formula: see text] ⩾75Gy was associated with a 12.5% risk of fistula at 3years versus 0-2.7% for lower doses (p>0.001). A [Formula: see text] <65Gy was associated with a two times lower risk of proctitis than [Formula: see text] ⩾65Gy.

CONCLUSIONS

Significant correlations were established between late rectal morbidity, overall and single endpoints, and dose-volume ( [Formula: see text] , [Formula: see text] ) and dose-point (D_ICRU) parameters. A [Formula: see text] ⩽65Gy is associated with more minor and less frequent rectal morbidity, whereas a [Formula: see text] ⩾75Gy is associated with more major and more frequent rectal morbidity.