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The purpose of this publication is to review the data of European neutron therapy facilities in the treatment of soft tissue sarcoma. In the past locally advanced soft tissue sarcoma was a common indication for neutron therapy in several European centers. Data from 1171 patients treated at 11 centers were analysed on the basis of published data or personal communication. Neutron therapy was of benefit especially for patients with primary radiotherapy of inoperable tumors, and with macroscopic disease after surgery. Local control was about 50% in these patients. These results are superior to those from photon therapy from the literature. Results for postoperative neutron therapy after R0- and R1-resection are similiar to those from photon therapy. The incidence of late side effects was considerably high in some neutron series. This is influenced by the treatment of most patients with first-generation machines of limited technical standard, and that in most cases large treatment volumes were irradiated.

Malignant salivary gland tumors are relatively rare and account for only 3%–4% of all head and neck cancers. Especially in adenoid cystic carcinoma, the incidence of local recurrence and distant metastases is influenced by the perineural spread of tumor. In advanced salivary gland tumors, surgery alone has a high incidence of local failure. The results of conventional radiotherapy are suboptimal in inoperable or not completely resected salivary gland tumors and in recurrent disease. The pooled data of some international series for low linear energy transfer radiation show a local control of only 28%. Especially in advanced salivary gland tumors, neutron therapy can improve local control. In Europe at least 570 patients with salivary gland tumors have been treated with neutrons alone or with combined modalities. The clinical data of different centers in Europe and the United States result in a similar local control rate of 67% in gross disease. An analysis of different European series shows on average a complication rate of 10.6% for severe radiation-related morbidity. Modern neutron machines and the use of three-dimensional treatment planning systems are now available in a few institutions and may further reduce side effects.

The aim of curative radiation oncology is to destroy all tumor cells without producing major damage in normal tissues. As early as 1936 the radiologist Hermann Holthusen related such uncomplicated local tumor control to tumor response on the one hand and normal tissue tolerance on the other (Fig. 1). Holthusen showed that both the probability of eradicating carcinoma of the skin and the probability of developing telangiectasia as a late normal tissue reaction increase as a sigmoid function of radiation dose. At each dose level the probability of uncomplicated local tumor control can be calculated as the product of the probability of achieving local tumor control and the probability of preventing normal tissue damage (Holthusen 1936; Busch 1987).

Conventional treatment of advanced bladder carcinoma included surgery, or preoperative irradiation combined with surgery. Results of cystectomy alone and irradiation/surgery for T3 tumors achieved 5-year survival rates up to 40% (Jacobi et al. 1983) and 40%–50% (van der Werf-Messing 1983). 5-Fluorouracil (5-FU), mitomycin C and cisplatin were shown to be useful as radiosensitizers in invasive bladder carcinoma. Rotman et al. (1987) and Russel et al. (1988) demonstrated an advantage for 5-year disease-free survival using irradiation and chemotherapy with 5-FU and mitomycin C. Sauer et al. (1988) and Shipley et al. (1984, 1985) reported similarly complete response rates with cisplatin and irradiation. However, cisplatin is a potentially more toxic drug, especially as regards its neurotoxicity and nephrotoxicity (Lelieveld et al. 1984).