Image-guided Adaptive Brachytherapy Research Articles

Impact of radiation dose and standardized uptake value of (18)FDG PET on nodal control in locally advanced cervical cancer

ABSTRACTBackground. Despite local control now exceeding 90% with image-guided adaptive brachytherapy (IGABT), regional and distant metastases continue to curb survival in locally advanced cervical cancer. As regional lymph nodes often represent first site of metastatic spread, improved nodal control could improve survival. The aim of this study was to examine optimal volume and dose of external beam radiotherapy (EBRT) to maximize regional control including dose contribution from IGABT.Material and methods. In total 139 patients from the EMBRACE study were analyzed. Individual nodal dose was determined by dose-maps from EBRT and IGABT. All PET/CT scans were re-evaluated and nodal maximal standard uptake value (SUVmax) was determined. Nodal failures were registered to planning scans and related to boosted nodes and treated volume. Relation between SUVmax and nodal control as well as the pattern of regional nodal failure were analyzed.Results. Eighty-four patients were node positive. Nine patients had all metastatic nodes surgically removed. Seventy-five patients had 209 nodes boosted with EBRT. Median nodal boost dose was 62 Gy EQD2 (53–69 Gy EQD2). Median SUVmax was 6 (2–22). No patients had persistent nodal disease, but six patients recurred in a boosted node. SUVmax was significantly higher in nodes that recurred (p = 0.02). However, there was no correlation to nodal dose or volume. Twenty-one patients had a nodal failure including para-aortic nodal (PAN) metastases above the irradiated volume. Nine patients had a PAN-only failure. Patients receiving ≤ 4 cycles of weekly cisplatin had higher risk of nodal failure (p < 0.01).Conclusion. Current RT practice provides a high level of control in both boosted nodes and the elective irradiated regional target. However, a high nodal SUVmax is a negative prognostic predictor for nodal control. Attention should be raised to administration of a complete schedule of concurrent chemotherapy as well as treatment of para-aortic nodes.

Assessment of Parametrial Response by Growth Pattern in Patients With International Federation of Gynecology and Obstetrics Stage IIB and IIIB Cervical Cancer: Analysis of Patients From a Prospective, Multicenter Trial (EMBRACE)

To assess disease response along the parametrial space according to tumor morphology in patients with International Federation of Gynecology and Obstetrics (FIGO) stage IIB and IIIB cervical cancer at the time of image-guided adaptive brachytherapy. Patients with FIGO stage IIB and IIIB cervical cancer registered as of November 2013 in the EMBRACE study were evaluated. Tumors were stratified according to morphologic subtype on magnetic resonance imaging (expansive and infiltrative), and the characteristics of those subtypes were analyzed. Parametrial involvement at diagnosis and at brachytherapy was evaluated, and the response to chemo-radiotherapy was classified as good, moderate, or poor. The response grade was compared between the 2 groups and analyzed with regard to tumor volumes, and dosimetric parameters. A total of 452 patients were evaluated, of whom 186 had expansive growth type and 266 had infiltrative morphology. Patients with infiltrative tumors had more extensive disease, as indicated by a higher rate of FIGO stage IIIB disease, as well as radiologic evidence of extension into the distal parametrial space and to the pelvic side wall on magnetic resonance imaging. Cervical necrosis was more common in the infiltrative group. Good response was more common in the expansive group (34% vs 24%; P=.02), and poor response was more common in the infiltrative group (11% and 19%; P=.02). Mean gross tumor volume at diagnosis was equal in both groups (51.7 cm(3)). The high-risk clinical target volume was larger in infiltrative tumors (37.9 cm(3) vs 33.3 cm(3), P=.005). The mean high-risk clinical target volume D90 was slightly higher in expansive tumors (92.7 Gy and 89.4 Gy, P<.001). Infiltrative tumors are more advanced at presentation and respond less favorably to chemo-radiotherapy when compared with expansive tumors that are more or less equivalent in size. The use of image-guided adaptive brachytherapy allows achieving reasonably high doses in both groups.

Evaluation of planning aims and dose prescription in image-guided adaptive brachytherapy and radiochemotherapy for cervical cancer: Vienna clinical experience in 225 patients from 1998 to 2008

ABSTRACTBackground. To assess planning aims (PAs) and dose prescription in image-guided adaptive brachytherapy (IGABT) of cervical cancer and investigate potential impact on clinical outcome.Material and methods. Our study population consists of 225 consecutive cervical cancer patients (FIGO stages IB–IVA) treated between 1998 and 2008 at the Medical University of Vienna by external beam radiotherapy (EBRT) ± chemotherapy and IGABT. For this retrospective study, patients were stratified into two treatment groups: PA+ group, all dose constraints fulfilled for prescription; PA-, one or more dose constraints not fulfilled for prescription. The following dose constraints (EBRT+ IGABT) were applied: clinical target volume (CTV)HR D90 ≥ 85 Gy, D2cm3 Rectum < 70 Gy, D2cm3 Bladder < 90 Gy. Differences in patient, tumor and treatment characteristics and clinical outcome (event: local failure or grade 3 + 4 toxicity) were compared between Group 1 and 2. Further, the impact of learning period (1998–2000) and protocol period (2001–2008) on the fulfillment of PAs for dose prescription and clinical outcome was analyzed.Results. In the PA+ group there were 77 (34%) and in the PA- group 148 (66%) patients. In the PA- group, CTVHR D90 < 85 Gy was prescribed in 82 patients, D2cm3 bladder > 90 Gy was prescribed in 80 patients and D2cm3 Rectum > 70 Gy in 60 patients. Fulfillment of the PA for dose prescription improved from 4% in the learning period to 48% in the protocol period. The five-year event-free interval was 64% in the learning period and 84% in the protocol period (p = 0.008).Conclusion. Fulfillment of all PAs for dose prescription is challenging – especially in patients with more advanced tumors. However, with growing experience fulfillment of PA for dose prescription can be significantly increased (learning and protocol period). Such increase in fulfilling PA for dose prescription is followed by a significant improvement in clinical outcome.

Pulsed-dose rate image-guided adaptive brachytherapy in cervical cancer: Dose–volume effect relationships for the rectum and bladder

PurposeTo establish dose–volume effect correlations for late bladder and rectum side effects in patients treated for locally advanced cervical cancer with concomitant chemoradiation followed by pulsed-dose rate image-guided adaptive brachytherapy. Material and methodsThe dosimetric data, converted in 2Gy equivalent, from 217 patients were confronted to late morbidity defined as any event lasting or occurring 90days after treatment initiation. Toxicity was assessed using the CTC-AE 3.0. Probit analyses and Log rank tests were performed to assess relationships. ResultsOne hundred and sixty-one urinary and 58 rectal events were reported, affecting 98 (45.1%) and 51 (23.5%) patients, respectively. Cumulative incidences for grade 2–4 bladder and rectal morbidity were 24.3% and 9.6% at 3years, respectively. Significant relationships were observed between grade 2–4 and 3–4 events and D0.1cm3 and D2cm3 for the bladder and between grade 1–4 and 2–4 event probability and rectal D2cm3. The effective doses for 10% grade 2–4 morbidity were 65.3Gy (59.8–81.3), and 55.4Gy (15.7–63.6), respectively, for the rectum and bladder. Without considering urinary and rectal incontinence, for which the pertinence of correlating them with D2cm3 is questionable, ED10 were 68.5Gy (62.9–110.6) and 65.5Gy (51.4–71.6Gy). When sorting patients according to D2cm3 levels, patients with high D2cm3 had significantly lower morbidity free survival rates for grade 1–4 and 2–4 urinary and rectal morbidity. ConclusionSignificant dose–volume effect relationships were demonstrated between the modern dosimetric parameters and the occurrence of late rectal and urinary morbidity in patients treated with pulsed-dose-rate brachytherapy. Further studies are required to refine these relationships according to clinical cofactors, such as comorbidities.

OC-0129: Image-guided adaptive brachytherapy in cervical cancer: towards a personalization of planning aims

OC-0129: Image-guided adaptive brachytherapy in cervical cancer: towards a personalization of planning aims

EP-1601: Impact of dose constraints on local control and G4 toxicity in image-guided adaptive brachytherapy for cervix cancer

EP-1601: Impact of dose constraints on local control and G4 toxicity in image-guided adaptive brachytherapy for cervix cancer

PD-0181: Image-guided adaptive brachytherapy for cervix cancer: higher target dose by increasing planning aim

PD-0181: Image-guided adaptive brachytherapy for cervix cancer: higher target dose by increasing planning aim

OC-0276: Comparison of MRI, TRUS and CT for target definition in image-guided adaptive brachytherapy of cervical cancer

OC-0276: Comparison of MRI, TRUS and CT for target definition in image-guided adaptive brachytherapy of cervical cancer

Impact of treatment time and dose escalation on local control in locally advanced cervical cancer treated by chemoradiation and image-guided pulsed-dose rate adaptive brachytherapy

PurposeTo report the prognostic factors for local control in patients treated for locally advanced cervical cancer with image guided pulsed-dose rate brachytherapy. Materials/methodsPatients treated with curative intent by a combination of external beam radiotherapy and pulsed-dose rate brachytherapy were selected. Local failure was defined as any relapse in the cervix, vagina, parametria, or uterus during follow-up. Prognostic factors were selected based on log rank tests and then analyzed with a Cox model. Dose/effect correlations were performed using the probit model. ResultsTwo hundred and twenty-five patients treated from 2006 to 2011 were included. According to the FIGO classification, 29% were stage IB, 58% stage II, 10% stage III, and 3% stage IVA; 95% received concomitant chemotherapy. Thirty patients were considered having incomplete response or local failure. Among the selected parameters, D90 for HR-CTV, D90 for IR-CTV, the overall treatment time, the TRAK, and the HR-CTV volume appeared significantly correlated with local control in univariate analysis. In multivariate analysis, overall treatment time >55days and HR-CTV volume >30cm3 appeared as independent. The probit analysis showed significant correlations between the D90 for both CTVs, and the probability of achieving local control (p=0.008 and 0.024). The thresholds to reach to warrant a probability of 90% of local control were 85Gy to the D90 of the HR-CTV and 75Gy to 90% of the IR-CTV (in 2Gy equivalent, α/β=10). To warrant the same local control rate, the D90 HR-CTV should be significantly increased in stage III–IV tumors, in case of HR-CTV >30cm3, excessive treatment time, or tumor width at diagnosis >5cm (97, 92, 105, and 92Gy respectively). ConclusionsOverall treatment time and HR-CTV volume were independent prognostic factors for local control. The D90 for HR and IR CTV were significantly correlated with local control, and D90 HR-CTV should be adapted to clinical criteria.

D2cm³/DICRU ratio as a surrogate of bladder hotspots localizations during image-guided adaptive brachytherapy for cervical cancer: assessment and implications in late urinary morbidity analysis.

To evaluate the efficiency and potential implications of the lowest dose evaluated in the maximally exposed 2cm(3) of the bladder/dose evaluated at the International Commission for Radiation Units and Measurements (ICRU) bladder point (D2cm(3)/DICRU) ratio as surrogate to locate the D2cm(3) in patients treated with MRI-guided adaptive brachytherapy for cervical cancer. The D2cm(3) area of the bladder was located in 69 patients, using the Digital Imaging and Communications in Medicine coordinates of its barycenter, with respect to the ICRU bladder point. The D2cm(3)/DICRU ratio was correlated with the longitudinal coordinate of the D2cm(3). Afterward, the ratio was used in a retrospective cohort of 216 patients to evaluate its impact in dose-effect analyses for late urinary incontinence. The mean position of the D2cm(3) was 1.73±0.98 cm cranially, 0.59±0.65 cm backwardly, and 0.02±0.89 cm to the right of the ICRU point. It was located above the ICRU point in 95.7% of the patients. Its position was lower in patients with vaginal involvement at diagnosis (p=0.03). The D2cm(3)/DICRU ratio was correlated with the position of the D2cm(3) (R²=0.716, p<10(-6)). In speculating that a ratio greater than one would predict a D2cm(3) located above the ICRU point, the sensibility, specificity, positive, and negative predictive values were 95.2%, 100%, 100%, and 66.8%, respectively. Among the retrospective cohort, 85 patients had a ratio lower than 1.1, reflecting a D2cm(3) located in the lower bladder. In these patients, analyses showed significant dose relationship with Grade 2-4 incontinence (p=0.017), whereas no correlation was demonstrated in the remaining patients. The D2cm(3)/DICRU ratio is a relevant surrogate to estimate the localization of the D2cm(3). Significant dose-effect correlations for incontinence were established in patients with low values for this ratio.

Health related quality of life and patient reported symptoms before and during definitive radio(chemo)therapy using image-guided adaptive brachytherapy for locally advanced cervical cancer and early recovery — A mono-institutional prospective study

ObjectiveTo evaluate health-related quality of life (HR-QoL) and patient reported symptoms (PRS) before, during and early after treatment with external-beam radiotherapy (EBRT), chemotherapy and image-guided adaptive brachytherapy (IGABT) for locally advanced cervical cancer. MethodsIn fifty consecutive patients, HR-QoL and PRS were prospectively assessed with the EORTC-QLQ-C30+CX24 questionnaire prior to and during treatment, one week after IGABT and three months thereafter. HR-QoL was compared to an age-matched, female normative reference population. Prevalence rates of individual PRS are presented and defined as “substantial”, if reported as “quite a bit” or “very much”. ResultsGlobal health status and physical and role functioning show a highly significant decline during treatment (p≤0.001), before returning to near the baseline levels three months after end of treatment. Compared to the reference population, the global health status and emotional and role functioning remain impaired. The most frequently reported substantial PRS during active treatment are: fatigue (78%), diarrhea (68%), urinary frequency (60%) and nausea (54%); these recover to some degree three months after end of treatment. However, fatigue remains increased (50%) and an onset of hot flashes (44%), sexual worries (38%) and limb edema (22%) is observed. ConclusionsSeveral impairments in HR-QoL and PRS were found during definitive radio(chemo)therapy with IGABT, with different patterns of progress over time and signs of recovery three months thereafter, although some aspects of functional HR-QoL remain impaired. These findings support a comprehensive patients' counseling on what to expect and how to organize professional, social and family life and plan additional support during this period.

Dose and Volume Response for Local Control in Locally Advanced Cervical Cancer Treated With EBRT Combined With MRI-Guided Adaptive Brachytherapy

Currently there is no broad consensus on dose planning aims and dose prescription in image guided adaptive brachytherapy (IGABT) in locally advanced cervical cancer. Planning aims vary from 75 Gy and up to > 85 Gy total EQD2 to high risk clinical target volume (HR CTV) according to institutional practice. This study analyzes dose and volume response for local control in cervix cancer with the purpose to provide evidence for dose planning aims for HR CTV, GTV and intermediate (IR) CTV.

Improved survival of patients with cervical cancer treated with image-guided brachytherapy compared with conventional brachytherapy

ObjectiveSince the Group Européen de Curiethérapie and the European Society for Radiotherapy and Oncology (GEC–ESTRO) published recommendations for 3D MRI-based image-guided adaptive brachytherapy (IGBT) in the treatment of cervical cancer, many institutions have implemented this technique and favourable results were documented. We investigated if introduction of IGBT in our centre indeed improved treatment outcomes and reduced toxicity compared to conventional brachytherapy (CBT). MethodsA retrospective analysis was done of outcomes of patients with stage IB-IVA cervical cancer treated with primary radiation therapy with curative intent between 2000 and 2012. Outcome measures were overall and disease-free survival, pelvic control, distant metastasis and treatment related adverse events (AE). Results126 patients were analysed; 43 had been treated with CBT between 2000–2007, and 83 with IGBT between 2007–2012. External beam radiation (mean; 46.6Gy) was combined with concurrent weekly cisplatin (51.6%), or hyperthermia (24.6%); radiation alone was used in 23.8%. Median follow-up was 121.8months for CBT patients, vs. 42.3months for IGBT. Complete remission was achieved in 83.7% of patients in the CBT group and in 98.8% of IGBT patients (p<0.01). Overall survival at 3years was 51% and 86%, respectively (p=0.001). Pelvic recurrence was found in 32% vs. 7% (p<0.001). Most patients had low grade adverse events. High grade (3–4) AE occurred in 15.4% vs. 8.4% at 3years (p=0.06). ConclusionIntroduction of IGBT for cervical cancer has led to significantly increased 3-year locoregional control and survival rates, whilst reducing late morbidity.

Toward four-dimensional image-guided adaptive brachytherapy in locally recurrent endometrial cancer.

To evaluate clinical outcome and feasibility of a four-dimensional image-guided adaptive brachytherapy concept in patients with locally recurrent endometrial cancer. Forty-three patients with locally recurrent endometrial cancer were included. Treatment consisted of conformal external beam radiotherapy followed by a boost using pulsed-dose-rate brachytherapy (BT). Large tumors were treated with MRI-guided interstitial BT. Small tumors were treated with CT-guided intracavitary BT. The planning aim (total external beam radiotherapy and BT) for high-risk clinical target volume was D90>80Gy, whereas constraints for organs at risk were D2cc≤90Gy for bladder and D2cc≤70Gy for rectum, sigmoid, and bowel in terms of equivalent dose in 2Gy fractions. Median high-risk clinical target volume was 18cm(3) (range, 0-91). D90 was 82Gy (range, 77-88). D2cc to bladder, rectum, and sigmoid were 67Gy (range, 50-81), 67Gy (range, 51-77), and 55Gy (range, 44-68), respectively. Median followup was 30months (6-88). Two-year local control rate was 92% (standard error [SE], 5). Disease-free survival rate and overall survival rate was 59% (SE, 8) and 78% (SE, 7), respectively. Patients with low- to intermediate-risk for recurrence had a 2-year disease-free survival rate of 72% (SE, 9) compared with 42% (SE, 12) in patients with high risk for recurrence (p=0.04). Late morbidity Grade 3 was recorded in 5 (12%) patients. Four-dimensional image-guided adaptive brachytherapy is feasible in locally recurrent endometrial cancer. Local control rate is good. Systemic control remains a problem in patients with high risk for recurrence.

WE-F-BRD-01: HDR Brachytherapy II: Integrating Imaging with HDR

In recent years, with the advent of high/pulsed dose rate afterloading technology, advanced treatment planning systems, CT/MRI compatible applicators, and advanced imaging platforms, image-guided adaptive brachytherapy treatments (IGABT) have started to play an ever increasing role in modern radiation therapy. The most accurate way to approach IGABT treatment is to provide the infrastructure that combines in a single setting an appropriate imaging device, a treatment planning system, and a treatment unit. The Brachytherapy Suite is not a new concept, yet the modern suites are incorporating state-of-the-art imaging (MRI, CBCT equipped simulators, CT, and /or US) that require correct integration with each other and with the treatment planning and delivery systems. Arguably, an MRI-equipped Brachytherapy Suite is the ideal setup for real-time adaptive brachytherapy treatments. The main impediment to MRI-IGABT adoption is access to MRI scanners. Very few radiation oncology departments currently house MRI scanners, and even fewer in a dedicated Brachytherapy Suite. CBCT equipped simulators are increasingly offered by manufacturers as part of a Brachytherapy Suite installation. If optimized, images acquired can be used for treatment planning, or can be registered with other imaging modalities. This infrastructure is relevant for all forms of brachytherapy, especially those utilizing multi-fractionated courses ofmore » treatment such as prostate and cervix. Moreover, for prostate brachytherapy, US imaging systems can be part of the suite to allow for real-time HDR/LDR treatments. Learning Objectives: Understand the adaptive workflow of MR-based IGBT for cervical cancer. Familiarize with commissioning aspects of a CBCT equipped simulator with emphasis on brachytherapy applications Learn about the current status and future developments in US-based prostate brachytherapy.« less

Manifestation Pattern of Early-Late Vaginal Morbidity After Definitive Radiation (Chemo)Therapy and Image-Guided Adaptive Brachytherapy for Locally Advanced Cervical Cancer: An Analysis From the EMBRACE Study

Brachytherapy in the treatment of locally advanced cervical cancer has changed substantially because of the introduction of combined intracavitary/interstitial applicators and an adaptive target concept, which is the focus of the prospective, multi-institutional EMBRACE study (www.embracestudy.dk) on image-guided adaptive brachytherapy (IGABT). So far, little has been reported about the development of early to late vaginal morbidity in the frame of IGABT. Therefore, the aim of the present EMBRACE analysis was to evaluate the manifestation pattern of vaginal morbidity during the first 2 years of follow-up. In total, 588 patients with a median follow-up time of 15 months and information on vaginal morbidity were included. Morbidity was prospectively assessed at baseline, every 3 months during the first year, and every 6 months in the second year according to the Common Terminology Criteria for Adverse Events, version 3, regarding vaginal stenosis, dryness, mucositis, bleeding, fistula, and other symptoms. Crude incidence rates, actuarial probabilities, and prevalence rates were analyzed. At 2 years, the actuarial probability of severe vaginal morbidity (grade ≥3) was 3.6%. However, mild and moderate vaginal symptoms were still pronounced (grade ≥1, 89%; grade ≥2, 29%), of which the majority developed within 6 months. Stenosis was most frequently observed, followed by vaginal dryness. Vaginal bleeding and mucositis were mainly mild and infrequently reported. Severe vaginal morbidity within the first 2 years after definitive radiation (chemo)therapy including IGABT with intracavitary/interstitial techniques for locally advanced cervical cancer is limited and is significantly less than has been reported from earlier studies. Thus, the new adaptive target concept seems to be a safe treatment with regard to the vagina being an organ at risk. However, mild to moderate vaginal morbidity is still pronounced with currently applied IGABT, and it needs further attention.

Generalized Equivalent Uniform Dose to Evaluate Overall OAR Doses of EBRT and 3D Image-Guided Adaptive HDR Brachytherapy for Cervical Cancer

As IMRT and different intracavitary applicators are being widely used, the assumption that a maximal dose (D2cc) represents whole DVH of integrated EBRT and brachytherapy plans' dose map, begins to lose its rationale. When EBRT and HDR brachytherapy are integrated, we hypothesize a generalized equivalent uniform dose (gEUD) that is a single value, accounting for an organ's volume effect and DVH can have a higher statistical correlation with predicted normal tissue complication probability (NTCP) than current overall D2cc values.

Distant metastasis in patients with cervical cancer after primary radiotherapy with or without chemotherapy and image guided adaptive brachytherapy

ObjectiveThe aim of this study is to investigate patterns of distant relapse after primary radiochemotherapy in cervical cancer patients. MethodsAll patients with cervical cancer treated in curative intent with external beam radiotherapy +/− chemotherapy and image-guided adaptive brachytherapy between January 1998 and June 2009 at the Medical University of Vienna were included in this retrospective analysis. Patients with locoregional recurrences were excluded from this study. Presence, site of and time to distant metastases were recorded. For identifying prognostic factors, uni- and multivariate analyses using Cox regression analysis were performed. Based on the result from the multivariate analysis, patients were stratified into a high and a low risk group. The Kaplan–Meier method was used to estimate distant-metastasis-free-survival in the overall cohort, in the risk groups and for analysing the impact of chemotherapy within the risk groups. ResultsA total number of 189 patients were included in this study. After a median follow-up of 54months, 49 patients developed distant metastases. Overall, distant-metastasis-free-survival 5years after treatment was 73%. FIGO stage, lymph node status and the extent of tumour regression during treatment were significant predictors for distant metastasis. Distant-metastasis-free-survival 5years after treatment was 91% and 60% in the low and high risk groups, respectively. The number of the cycles of chemotherapy had a significant impact on the occurrence of distant metastasis in high risk patients, but not in low risk patients. ConclusionPatients with high risk factors have a 40% probability of developing distant metastasis within 5years. In these patients, decreasing the number of cycles of cisplatin may increase their probability of developing distant metastasis.

MRI findings at image guided adaptive cervix cancer brachytherapy: radiation oncologist's perspective.

Magnetic resonance imaging (MRI) represents the reference imaging modality for image guided adaptive brachytherapy (IGABT) of cervix cancer. Accurate interpretation of pre-treatment MRI is required for proper understanding of the tumor extent and topography at IGABT. Planning and optimal timing of the application begins already before treatment, and may need to be adapted during external beam irradiation (EBRT) according to additional clinical and/or radiological findings. The level of MRI utilization in IGABT depends on the infrastructural capabilities of individual centers, ranging from no use at all to repetitive imaging during EBRT and each IGABT fraction. In this article, we summarize the role of different imaging modalities and practical aspects of MRI interpretation in cervix cancer IGABT, concentrating on the systematic evaluation of post-insertion images. MRI with the applicator in place from the radiation oncologist’s perspective should begin with immediate identification of eventual complications of the application procedure and assessment of the implant adequacy, followed by appropriate corrective measures in case of adverse findings. Finally, the tumor extent, topography, and treatment response should be evaluated in the context of initial clinical and radiological findings to allow for an appropriate selection and delineation of the target volumes.

Image guided adaptive brachytherapy for cervical cancer: dose contribution to involved pelvic nodes in two cancer centers.

PurposeThe goal of this study was to determine the dose contributions from image guided adaptive brachytherapy (IGABT) to individual suspicious pelvic lymph nodes (pLNN) in cervical cancer patients. Data were collected in two cancer centers, University of Pittsburgh Cancer Institute (UPCI) and University Medical Center Utrecht (UMCU).Material and methods27 and 15 patients with node positive cervical cancer treated with HDR (high dose rate) or PDR (pulsed dose rate)-IGABT were analyzed. HDR-IGABT (UPCI) was delivered with CT/MRI compatible tandem-ring applicators with 5.0-6.0 Gy × five fractions. PDR-IGABT (UMCU) dose was delivered with Utrecht tandem-ovoid applicators with 32 × 0.6 Gy × two fractions. Pelvic lymph nodes with short axis diameter of ≥ 5 mm on pre-treatment MRI or PET-CT were contoured for all BT-plans. Dose contributions to individual pLNN expressed as D90 (dose to 90% of the volume) were calculated from dose-volume histograms as absolute and relative physical dose (% of the reference dose) for each fraction. For each node, the total dose from all fractions was calculated, expressed in EQD2 (equivalent total dose in 2 Gy fractions).ResultsFifty-seven (UPCI) and 40 (UMCU) individual pLNN were contoured. The mean D90 pLNN was 10.8% (range 5.7-25.1%) and 20.5% (range 6.8-93.3%), respectively, and therefore different in the two centers. These values translate into 2.7 Gy (1.3-6.6 Gy) EQD2 and 7.1 Gy (2.2-36.7 Gy) EQD2, respectively. Differences are caused by the location of the individual nodes in relation to the spatial dose distribution of IGABT, differences in total dose administered and radiobiology (HDR versus PDR).ConclusionsThe IGABT dose contribution to individual pelvic nodes depends on patient and treatment related factors, and varies considerably.