PTC CLINIC
Information for Healthcare Professionals

Due to the presence of many high-risk structures around the ENT or orofacial tumor with a limited tolerance to ionizing radiation (spinal cord, salivary glands, brain stem, swallowing tract, respiratory tract, mandible, oral cavity or in some cases eyes, optic nerves, retina, optic chiasm, brain, with limits of tolerance ranging from 40 to 55 Gy), situations may often occur in which it is not possible to administer a sufficient tumoricidal dose of radiation without increasing the risk of damage to the surrounding healthy tissues.

This is especially true for tumors of the paranasal sinuses, nasopharynx and skull base, which are close to the eye or optic tract, or brain stem, for tumors spreading to the areas near the spinal canal with the risk of radiation damage to the spinal cord and large tumors with the involvement of the lower cervical or upper mediastinal lymph nodes, where there is a risk of damage to the larynx, esophagus, swallowing tract and spinal cord.

In some cases, highly radioresistant tumors are present (such as sarcomas, melanomas, adenoid cystic carcinomas) that should be irradiated with a high (>74 Gy) radiation dose and for which it is not possible to administer a sufficient dose of conventional photon radiation therapy due to the proximity of high-risk organs to the target volume. These tumors are considered incurable by radiation therapy.

Another complicated situation may arise in patients with recurrent ENT/orofacial tumors after previous radiotherapy, when it is necessary to repeat the irradiation (reradiation) in a situation where dose limits for high-risk organs have been reached in the previous series of RT (doses delivered to certain organs during the individual RT series are added together over time).