O. McArdle

Image guided brachytherapy in locally advanced cervical cancer: Improved pelvic control and survival in RetroEMBRACE, a multicenter cohort study

PURPOSE Image guided brachytherapy (IGBT) for locally advanced cervical cancer allows dose escalation to the high-risk clinical target volume (HRCTV) while sparing organs at risk (OAR). This is the first comprehensive report on clinical outcome in a large multi-institutional cohort. PATIENTS AND METHODS From twelve centres 731 patients, treated with definitive EBRT±concurrent chemotherapy followed by IGBT, were analysed. Kaplan-Meier estimates at 3/5years were calculated for local control (LC, primary endpoint), pelvic control (PC), overall survival (OS), cancer specific survival (CSS). In 610 patients, G3-4 late toxicity (CTCAEv3.0) was reported. RESULTS Median follow up was 43months, percent of patients per FIGO stage IA/IB/IIA 22.8%, IIB 50.4%, IIIA-IVB 26.8%. 84.8% had squamous cell carcinomas; 40.5% lymph node involvement. Mean EBRT dose was 46±2.5Gy; 77.4% received concurrent chemotherapy. Mean D90 HRCTV was 87±15Gy (EQD210), mean D2cc was: bladder 81±22Gy, rectum 64±9Gy, sigmoid 66±10Gy and bowel 64±9Gy (all EQD23). The 3/5-year actuarial LC, PC, CSS, OS were 91%/89%, 87%/84%, 79%/73%, 74%/65%. Actuarial LC at 3/5years for IB, IIB, IIIB was 98%/98%, 93%/91%, 79%/75%. Actuarial PC at 3/5years for IB, IIB, IIIB was 96%/96%, 89%/87%, 73%/67%. Actuarial 5-year G3-G5 morbidity was 5%, 7%, 5% for bladder, gastrointestinal tract, vagina. CONCLUSION IGBT combined with radio-chemotherapy leads to excellent LC (91%), PC (87%), OS (74%), CSS (79%) with limited severe morbidity.

A cardiac contouring atlas for radiotherapy.

Background and purpose The heart is a complex anatomical organ and contouring the cardiac substructures is challenging. This study presents a reproducible method for contouring left ventricular and coronary arterial segments on radiotherapy CT-planning scans. Material and methods Segments were defined from cardiology models and agreed by two cardiologists. Reference atlas contours were delineated and written guidelines prepared. Six radiation oncologists tested the atlas. Spatial variation was assessed using the DICE similarity coefficient (DSC) and the directed Hausdorff average distance (d→H,avg). The effect of spatial variation on doses was assessed using six different breast cancer regimens. Results The atlas enabled contouring of 15 cardiac segments. Inter-observer contour overlap (mean DSC) was 0.60–0.73 for five left ventricular segments and 0.10–0.53 for ten coronary arterial segments. Inter-observer contour separation (mean d→H,avg) was 1.5–2.2 mm for left ventricular segments and 1.3–5.1 mm for coronary artery segments. This spatial variation resulted in <1 Gy dose variation for most regimens and segments, but 1.2–21.8 Gy variation for segments close to a field edge. Conclusions This cardiac atlas enables reproducible contouring of segments of the left ventricle and main coronary arteries to facilitate future studies relating cardiac radiation doses to clinical outcomes.

Impact of delineation uncertainties on dose to organs at risk in CT-guided intracavitary brachytherapy

PURPOSE This study quantifies the inter- and intraobserver variations in contouring the organs at risk (OARs) in CT-guided brachytherapy (BT) for the treatment of cervical carcinoma. The dosimetric consequences are reported in accordance with the current Gynecological Groupe Européen de Curiethérapie/European Society for Therapeutic Radiology and Oncology guidelines. METHODS AND MATERIALS A CT planning study of 8 consecutive patients undergoing image-guided BT was conducted. The bladder, rectum, and sigmoid were contoured by five blinded observers on two identical anonymized scans of each patient. This provided 80 data sets for analysis. Dosimetric parameters analyzed were D0.1 cc, D1 cc, and D2 cc. The mean volume of each OAR was calculated. These endpoints were compared between and within the observers. The CT image sets from all patients were evaluated qualitatively. RESULTS The interobserver coefficient of variation for reported D2 cc was 13.2% for the bladder, 9% for the rectum, and 19.9% for the sigmoid colon. Unlike the variation seen in bladder and rectal contours, which differed largely in localization of the organ walls on individual slices, sigmoid colon contours demonstrated large differences in anatomic interpretation. CONCLUSIONS Variation in recorded D2 cc to the bladder and rectum is comparable with the previous published results. Inter- and intraphysician variations in reported D2 cc is high for the sigmoid colon, reflecting varying interpretation of sigmoid colon anatomy. Variation in delineation of the OARs may influence treatment optimization and is a potential source of uncertainty in the image-guided BT planning and delivery process.

An atlas to aid delineation of para-aortic lymph node region in cervical cancer: Design and validation of contouring guidelines

INTRODUCTION Previous studies have investigated the anatomical distribution of para-aortic lymph nodes (PAN) in patients with cervical cancer. However, an atlas for accurate clinical target volume (CTV) delineation has yet to be defined. The purpose of this study was to design and verify a computerized tomography (CT) atlas to provide guidance for contouring the PAN CTV in patients with cervical cancer. MATERIALS AND METHODS This prospective study included 21 cervical cancer patients (design cohort) with 39 pathological PAN identified on (18)F-FDG PET-CT. PAN [left lateral para-aortic (LLPA), aorto-caval (AC), right para-caval (RPC) nodes] were delineated on CT simulation scans. Measurements were taken from the volumetric centre of the nodes to the edge of aorta and inferior vena-cava (IVC). Initially the aorta and IVC were expanded by the mean distance to the lymph node centre to create a CTV. Expansion margins were then increased asymmetrically until the CTV resulted in a clinically acceptable number of PAN included. The CTV was validated on a further 10 patients (validation cohort) with 29 PAN. A detailed contouring guide and accompanying visual atlas for elective PAN CTV delineation was created based on the validated margins. RESULTS For the design cohort (n = 21 patients, 39 PAN), the mean distance from the centre of the node to the aorta was 8 mm (range 4-17) for both LLPA (range 4-17) and AC (range 4-15) regions. Mean distance from the IVC to the centre of the nodes was 5 mm (range 4-6) in the RPC region and 6 mm (range 3-15) in the AC region. No PAN was superior to the T12-L1 interspace or the left renal vein or inferior to the L5-S1 interspace. For validation cohort (n = 10 patients, 29 PAN), mean distance from centre of the node to the aorta was 9 mm (range 5-15) in the LLPA region, 7 mm (range 6.5-14) in the AC region. Mean distance from the ICV to the centre of the nodes was 3 mm (range 2.5-4) in the RPC region and 5 mm (range 3-10) in the AC region. A CTV expansion from the aorta of 10 mm circumferentially and 15 mm laterally, and from the IVC of 8 mm anteromedially and 6 mm posterolaterally resulted in coverage of 97% (38/39) of PAN in the design cohort. On prospective validation, the described CTV included 97% (28/29) of PAN in the validation cohort. CONCLUSION We propose the following PAN CTV; expansion from aorta of 10 mm circumferentially except 15 mm laterally, expansion from the IVC of 8 mm anteromedial and 6 mm posterolaterally. The suggested CTV includes 97% (28/29) PAN in a validated patient cohort. A detailed guide and accompanying visual atlas is provided to aid delineation of the PAN CTV in patients with cervical cancer.