All of the patients in 3 years of fast neutron therapy at Hammersmith Hospital have had such advanced or radioresistant tumors that they were thought unlikely to respond to low L.E.T. radiation. Twenty percent of those referred have been too ill to be treated or have been unable to complete the course of treatment. Of 238 patients who completed their treatment by January, 1973, 180 died less than 1 year after treatment of metastases or other causes, but in 135 of these, the tumors were either regressing or had completely regressed at the time of death. Fifty‐eight patients survived for more than a year with no sign of tumor in the treated area, including 20 with adenocarcinoma, 14 with well‐differentiated squamous cell carcinoma, 9 with sarcomas, and 7 with salivary gland tumors. Twenty‐two tumors definitely recurred or were residual, but all these received a dose which was less than the standard of 1440 rads in 12 treatments over 26 days. Eleven of the 97 patients who survived more than 6 months after treatment developed necrosis, but a precipitating factor was present in every case. Details of the results of 26 patients with buccal cavity tumors and of 31 patients with inoperable carcinoma of the stomach are given. Early results of a randomized clinical trial of the treatment of advanced tumors of the head and neck show that a greater number of tumors completely regressed with neutron than with supervoltage treatment. The results are statistically significant, but more patients are required and the trial is continuing. The techniques of fast neutron therapy are much more demanding than those of low L.E.T. radiation; the margin is narrow between the dose leading to recurrence and that resulting in necrosis. Scrupulous attention to planning and treatment is necessary in every case.
