A model of mandibular irradiation in the rabbit: preliminary results

Radiotherapy is widely used in the treatment of head and neck cancers. Its major adverse effect is osteoradionecrosis, which can occur during the whole life of the patient, involving the vital prognosis. The aim of the study was to develop a model for irradiation of the rabbit mandible in order to have a better knowledge of radiotherapy-induced bone alterations and thus a better prevention and treatment of osteoradionecrosis. The control group consisted in 7 rabbits and was used to assess anatomical and histological parameters of the rabbit’s mandible. A first group of 14 rabbits was weekly irradiated at doses of 5.5 Gy during 5 weeks, at a total dose of 46.8Gy. Sacrifices were done at 1 week, 4 weeks, 12 weeks and 24 weeks. As histological analysis did not reveal statistical differences with the control group, a second group (3 rabbits) was weekly irradiated at 8.0, 8.5 and 9 Gy during 5 weeks. The first histological results seem to show vascular alterations, bone cells decrease and alterations of bone architecture. The role of intra alveolar collagen sponges, PRF®, ultrasounds and stem cells in bone regeneration after radiotherapy will be further studied. La radiotherapie est une modalite therapeutique utilisee quasi systematiquement dans le traitement des cancers des voies aerodigestives superieures. Son principal effet secondaire est l’osteoradionecrose, qui peut survenir tout au long de la vie du patient et compromettre le pronostic vital. Le but de ce travail est de mettre au point un modele d’irradiation des maxillaires chez le lapin afin de mieux connaitre la pathogenie de l’osteoradionecrose et proposer une prevention et des traitements plus efficaces. Un groupe controle de 7 lapins a permis de connaitre l’anatomie et l’histologie de la mandibule de lapin. Un premier groupe de 14 lapins a ete irradie a raison d’une seance hebdomadaire de 5.5 Gy pendant 5 semaines, soit un equivalent de dose de 46.8 Gy. Ils ont ete sacrifies a 1, 4, 12 et 24 semaines. L’analyse statistique n’ayant pas montre de differences significatives avec le groupe controle, un second groupe de 3 lapins a ete irradie a une seance hebdomadaire de 8.0, 8.5 et 98.0 Gy respectivement pendant 5 semaines. Les premiers resultats histologiques montrent une alteration vasculaire, la diminution du nombre de cellules osseuses et des modifications de l’architecture osseuse. Le role des eponges collageniques intra alveolaires, du PRF®, des ultrasons et des cellules souches sera etudie ulterieurement.