Mapping patterns of locoregional recurrence following contemporary treatment with radiation therapy for breast cancer: A multi-institutional validation study of the ESTRO consensus guideline on clinical target volume.

BACKGROUND AND PURPOSE: To validate the ESTRO guideline on clinical target volume (CTV) delineation for breast cancer using a multi-centre dataset. MATERIALS AND METHODS: Patients with axial imaging of gross locoregional recurrence (LRR) were identified from 10 participating institutions. All patients received RT, albeit not to all regional node. The location of LRR was transferred to the corresponding area on representative axial computed tomography images and compared with ESTRO-CTV. RESULTS: The locations of LRRs in 234 patients with 337 recurrence lesions were mapped. The ESTRO-CTV encompassed 97.6% of all LRRs, except in lymph node level 4 and the pectoralis muscle. Although 8.8% of level 4 failures occurred outside the ESTRO-CTV, cranial to the subclavian artery, all nodes were located within 6 mm cranially. Another 20% occurred posterolateral to anterior scalene muscles; however, 11/16 cases had simultaneous multiple lymph node recurrences, and 8/16 initially had N2-3 tumours. Local recurrence at the pectoralis muscle was prominent in patients undergoing mastectomy but not breast-conservation surgery (28% vs. 2.9%, P = .001). CONCLUSIONS: Our mapping data demonstrated that the ESTRO-CTV, with some considerations, successfully encompassed most LRRs in patients undergoing contemporary management, thus validating ESTRO-CTV to be valuable for highly conformal radiation therapy techniques.

Evaluation of variability in target volume delineation for newly diagnosed glioblastoma: a multi-institutional study from the Korean Radiation Oncology Group.

BACKGROUND: This study aimed for a collaborative evaluation of variability in the target volumes for glioblastoma, determined and contoured by different radiotherapy (RT) facilities in Korea. METHODS: Fifteen panels of radiation oncologists from independent institutions contoured the gross target volumes (GTVs) and clinical target volumes (CTVs) for 3-dimensional conformal RT or intensity-modulated RT on each simulation CT images, after scrutinizing the enhanced T1-weighted and T2-weighted-fluid-attenuated inversion recovery MR images of 9 different cases of glioblastoma. Degrees of contouring agreement were analyzed by the kappa statistics. Using the algorithm of simultaneous truth and performance level estimation (STAPLE), GTVSTAPLE and CTVSTAPLE contours were derived. RESULTS: Contour agreement was moderate (mean kappa 0.58) among the GTVs and was substantial (mean kappa 0.65) among the CTVs. However, each panels' GTVs and modification of CTVs regarding anatomical structures varied. Three-fourth of contoured panels' CTVs encompassed the peritumoral areas of T2-high signal intensity (T2-HSI). Nine of nine GTVSTAPLE encompased the surgical cavity and the T1-enhanced lesions. Eight of nine CTVSTAPLE encompassed the peritumoral T2-HSI area. The median MARGIN90 and the median MARGIN95 were 1.4 cm and 1.5 cm, respectively. CONCLUSIONS: Moderate to substantial agreement existed in target volumes for 3-dimensional or intensity-modulated RT determined by radiation oncologists in Korea. According to the estimated consensus contours, the initial CTV encompassed the GTV with margin less than 2.0 cm and the whole peritumoral areas of T2-HSI. The findings of our study propose the need for further studies and modified guidelines.