Postoperative radiotherapy after flap reconstructive surgery in patients with head and neck cancer: A retrospective monocentric study with flap delineation to assess toxicity and relapse.

PURPOSE: Flaps are increasingly used during reconstructive surgery of head and neck cancers to improve functional outcomes. There are no guidelines as to whether the whole flap or its anastomotic border should be included in the primary tumour target volume of postoperative radiotherapy to prevent local relapses. Relapse and toxicity rates can increase substantially if the whole flap received full dose. Our aim was to determine whether flaps were included in the primary tumour target volume and to report the patterns of relapse and toxicity. MATERIALS AND METHODS: Consecutive patients in 2014 through 2016, with or without a flap, receiving postoperative radiotherapy were selected in a retrospective monocentric control study. Flaps were homogenously delineated blind to treating radiation oncologists using a flap-specific atlas. Tumour recurrence, acute and late toxicity were evaluated using univariate and propensity score analyses. RESULTS: A hundred patients were included; 54 with a flap. Median flap volume included in the tumour volume was 80.9%. Twelve patients experienced local recurrences: six with a flap, among whom two within their flap (3.7%). Patients with flaps had larger median tumour volumes to be irradiated (25cm3 versus 58cm3, p<0.001) and higher acute/late toxicity rates (p<0.001) even after adjustment on biases (more advanced T stage, oral cavity, active smoking in patients with flaps). Locoregional recurrence and survival rates were similar between patients with/without a flap. CONCLUSION: Recurrences within a flap were rare in this series when including the whole flap body in the 60Gy-clinical target volume but inclusion of the flap in the primary tumour target volume increased toxicity. Multicentric studies are warranted.

Flap delineation guidelines in postoperative head and neck radiation therapy for head and neck cancers.

INTRODUCTION: Reconstructive surgery in head and neck cancers frequently involves the use of autologous flaps to improve functional outcomes. However, the literature suggests that postoperative radiotherapy deteriorates functional outcomes due to flap atrophy and fibrosis. Data on patterns of relapse after postoperative radiotherapy with a flap are lacking, resulting in heterogenous delineation of postoperative clinical target volumes (CTV). Flap delineation is unusual in routine practice and there are no guidelines on how to delineate flaps. Therefore, we aim to propose a guideline for flap delineation in head and neck cancers to assess dose-effects more accurately with respect to flaps. MATERIAL AND METHODS: Common flaps were selected. They were delineated by radiation oncologists and head and neck surgeons based on operative reports, on contrast-enhanced planning CTs and checked by a radiologist. Each flap was divided into its vascular pedicle and its soft tissue components (fat, fascia/ muscle, skin, bone). RESULTS: Delineation (body and pedicle) of Facial Artery Musculo-Mucosal, pectoralis, radial forearm, anterolateral thigh, fibula and scapula flaps was performed. Based on information provided in operative reports, i.e. tissue components, size and location, flaps can be identified. The various tissue components of each flap can be individualized to facilitate the delineation. CONCLUSION: This atlas could serve as a guide for the delineation of flaps and may serve to conduct studies evaluating dose-effects, geometric patterns of failure or functional outcomes after reconstructive surgery. Changes in postoperative CTV definitions might be needed to improve risk/benefit ratio in the future based on surgery-induced changes.

[Impact of reconstructive or minimal invasive surgery on the assessment of current definitions of postoperative clinical target volume for head and neck cancers]. / Impact de la chirurgie reconstructrice avec lambeaux et de la chirurgie mini-invasive sur la définition du volume cible anatomoclinique des cancers de la sphère ORL.

Advances in the reconstructive surgery and minimally invasive endonasal endoscopic surgery of head and neck is poorly evaluated in terms of their impact on radiotherapy planning and outcomes. These surgical advances have resulted in reduced morbidity with equivalent or better tumor control. In the absence of a recommendation on how to delineate target volumes in patients with flaps or to consider margins after endoscopic endonasal surgery, radiotherapy practices are inevitably heterogeneous. Efforts are needed to increase the therapeutic index of postoperative radiotherapy in these situations. We analysed the rare existing literature and outlined a preliminary basis for a recommendation. Strengthening of multidisciplinarity to accurately define target volumes in these complex and relatively new situations, and "delineation concertation meetings" between radiologists, surgeons and radiation oncologists could probably contribute to improved outcomes.