Management of Inoperable Malignant Neoplasms

For patients with inoperable salivary gland malignancy, radiation therapy has significant limitations but has been the mainstay of treatment. With standard photon radiation (X-rays), the 10-year loco-regional control (LRC) and overall survival rates are only ∼25%. Neutron radiation has potential biological advantages over photon radiation because it causes increased DNA damage, and studies of patients with inoperable salivary gland malignancy have shown improved 6-year LRC and overall survival of ∼60%. However, neutron radiation may also increase the risk of late toxicities, especially central nervous system toxicities after treatment of tumors involving the base of the skull. Proton radiation has potential physical advantages due to minimal exit dose through normal tissues, and a recent study has demonstrated 90% 5-year LRC after combined proton/photon radiation for adenoid cystic carcinoma involving the base of the skull. Stereotactic radiosurgery has also been used in combination with neutrons or standard photons as a technique to boost the skull base. The use of concurrent chemotherapy as a radiosensitizer has been considered based on extrapolation of data on squamous cell carcinomas, but further data are needed on inoperable salivary gland malignancies. Newer targeted therapies are also under investigation, and clinical trial enrollment is encouraged.