Fast neutron radiation for inoperable and recurrent salivary gland cancers

The current standard treatment of salivary gland cancers consists of surgical resection, with or without postoperative low linear energy transfer (LET) radiation, resulting in high locoregional control rates. However, tumor control prognosis is poor when conventional radiation is used alone for advanced, inoperable cases. An extensive review of the world's literature on fast neutron irradiation for inoperable, unresectable, or recurrent malignant salivary gland neoplasms is presented and compared with the experience using conventional low LET radiotherapy. The pooled data indicate a locoregional control rate of 67% for fast neutrons versus 25% for photons and/or electrons in the treatment of such advanced disease. The radiobiological rationale supporting this observed increase in tumor control is discussed. The overall significant late complication rate is 19%, but several suboptimal treatment factors were present that contributed substantially to the reported toxicity. With the modern machines and treatment techniques now available, the evidence overwhelmingly supports the role of fast neutron radiation as the treatment of choice for inoperable and recurrent salivary gland cancers.