Dose and volume impact on radiation-induced xerostomia.

Radiation-induced xerostomia consists in the chronic dryness of the mouth caused by parotid gland irradiation. Parotid glands produce approximately 60% of saliva while the rest is secreted by submandibular and accessory salivary glands. Methods of measuring the salivary output are essentially represented by 99mTc-pertechnate scintigraphy or simpler albeit less accurate methods in stimulated or unstimulated saliva. There are subjective and objective criteria of classification and grading of the secretion of saliva. Radiation-induced xerostomia, namely the residual salivary gland function is evidently associated with the mean dose absorbed. The salivary output tends to decrease after the end of radiotherapy. The partial dose-volume is substantially correlated with the mean dose to the whole gland. As for ipsilateral irradiation for head and neck cancer, conformal RT or IMRT allow to spare the contralateral parotid gland without increasing the risk of contralateral nodal recurrences. The monitoring system of late toxicity used by the authors is presented.

Biological factors and therapeutic modulation in brain tumor radiotherapy.

Diagnosticotherapeutic approaches aimed at the improvement of prognosis of the most aggressive brain tumors tend to include new tools of investigation. Functional imaging, biologic markers, radiosensitizers, the combination of different modalities of radiation therapy and chemotherapy are being experimented. These new approaches to the neoplastic metabolism require increased resources and a close follow-up during treatment to better define the biological target volume. More sophisticated and aggressive techniques as intensity modulated radiation therapy or brachycurietherapy can be suitably included in combined modality therapy.