[Conformal radiotherapy of brain tumors]

Conformal irradiation of brain tumours is based on the three-dimensional reconstruction of the targeted volumes and at-risk organ images, the three-dimensional calculation of the dose distribution and a treatment device (immobilisation, beam energy, collimation, etc.) adapted to the high precision required by the procedure. Each step requires an appropriate methodology and a quality insurance program. Specific difficulties in brain tumour management are related to GTV and CTV definition depending upon the histological type, the quality of the surgical resection and the medical team. Clinical studies have reported dose escalation trials, mostly in high-grade gliomas and tumours at the base of the skull. Clinical data are now providing a better knowledge of the tolerance of normal tissues. As for small tumours, the implementation of beam intensity modulation is likely to narrow the gap between conformal and stereotaxic radiotherapy.

rhBMP-collagen sponges as osteoinductive devices: effects of in vitro sponge characteristics and protein pI on in vivo rhBMP pharmacokinetics

Osteoinductive devices, comprised of biodegradable collagen scaffolds and recombinant human Bone Morphogenetic Proteins (rhBMPs), are being currently pursued for local bone induction. To better understand the biological performance of such devices, we have carried out a series of studies to investigate the effects of sponge properties and protein structural features on the pharmacokinetics of implanted rhBMPs. The results indicated little dependence of the rhBMP-2 pharmacokinetics on the in vitro determined sponge properties. The protein isoelectric point (pI), on the other hand, was found to significantly affect the initial implant retention of rhBMPs, but not the subsequent pharmacokinetics. A 100-fold difference in the implant-retained dose could be observed depending on the type of rhBMP implanted. We conclude that protein structural features are important variables controlling in vivo pharmacokinetics of rhBMPs, and possibly the osteoinductive potency of the devices.