Palliative radiotherapy of malignant melanoma with reactor fission neutrontherapy (RENT): A prospective study

To study the efficacy and safety of relatively low-dosed reactor fission ne utron therapy (RENT) at the research reactor of the Technical University Mu nich, we treated 33 superficial lesions of 20 patients with advanced malign ant melanoma by neutron beam alone (n = 22), mixed neutron/electron beam (n = 5), or by neutron beam after incomplete surgery (n = 6). Median tumor vo lume was 17.0 cm(3). Median dose for neutron beam alone was 8.0 Gy and for mixed beam 3.0 Gy n + 45.3 Gy e(-). Local tumor response, local control tim e, survival and treatment related toxicity were followed prospectively over a time period of 52 months. Overall response rate (CR;PR) after neutron be am alone and mixed beam therapy was 64% (CR: 36%) and 100% (CR: 60%), respe ctively. Observed differences between complete (CR) and incomplete (PR, NC) responding lesions were as follows: median tumor volume: 2.0 vs. 51.5 cm(3 ), local control time: 13.3 vs. 3.7 months, median survival: 19.8 vs. 9.0 m onths. No severe acute or late sequelae could be observed. In conclusion, l ow-dosed RENT is an effective and well tolerated palliative treatment of su perficial malignant melanoma utilizing the biologic advantage of diminished cellular repair capacity. Because melanoma lesions of small size (less tha n or equal to 6 cm(3)) tend to respond completely, neutron beam should be p erformed at an early stage. (C) 1999 Wiley-Liss, Inc.