Neon ion radiotherapy: Results of the phase I/II clinical trial

Abstract

Neon ion radiotherapy possesses biologic and physical advantages over megavoltage X rays. Biologically, the neon beam reduces the oxygen enhancement ratio and increases relative biological effectiveness. Cells irradiated by neon ions show less variation in cell-cycle related radiosensitivity and decreased repair of radiation injury. The physical behavior of heavy charged particles allows precise delivery of high radiation doses to tumors while minimizing irradiation of normal tissues. In 1979 a Phase I-II clinical trial was started at Lawrence Berkeley Laboratory using neon ions to irradiate patients for whom conventional treatment modalities were ineffective. By the end of 1988 a total of 239 patients had received a minimum neon physical dose of 1000 cGy (median follow-up for survivors 32 months). Compared with historical results, the 5-year actuarial disease-specific survival (DSS 5) and local control (LC 5) rates suggest that neon treatment improves outcome for several types of tumors: a) advanced or recurrent macroscopic salivary gland carcinomas (DSS 5 59%; LC5 61%); b) paranasal sinus tumors (DSS 5 69%; LC 5 69% for macroscopic disease); c) advanced soft tissue sarcomas (DSS 5 56%, LC 5 56% for macroscopic disease); d) macroscopic sarcomas of bone (DSS 5 45%; LC5 59%); e) locally advanced prostate carcinomas (DSS 5 90%; LC 5 75%); and f) biliary tract carcinomas (DSS 5 28%; LC 5 44%). Treatment of malignant gliomas, pancreatic, gastric, esophageal, lung, and advanced or recurrent head and neck cancer has been less successful; results for these tumors appear no better than those achieved with conventional x-ray therapy. These findings suggest that Phase III trials using the neon beam should be implemented for selected malignancies.