Boron neutron capture therapy of skin melanomas at the RA-6 reactor: A procedural approach to beam set up and performance evaluation for upcoming clinical trials

This article reports on the progress of the modeling and experimental characterization of the RA-6 reactor neutron beam, designed for the upcoming BNCT clinical trials of skin melanoma, and presents the first theoretical analysis of such beam performance. The aspects relating to surface source modeling and assessment, beam dosimetry,treatment planning system calibration, and treatment planning optimization are presented herein. Several methods and criteria were established in order to provide guidance for future clinical studies conducted in this facility. Following a realistic model, the theoretical analysis was based on a clinical case of malignant melanoma in extremities. Owing to the complex geometry of the tumor, this particular clinical case represents one of the most difficult lesions to be treated. This article discusses the thorough evaluation stage that has led to the optimization of the treatment planning procedure. Two candidate plans were proposed, and dose–volume distributions in the target volume were evaluated on the basis of the application of a series of criteria that define the critical normal structures which limit the dose delivered. In spite of the complexity of the clinical case under review, results showed that only 4% of the tumor volume is underdosed in cases of mean blood 10 B concentration values, even in the most unfavorable analysis. The overall results suggest that this BNCT facility is prepared to rigorously explore the clinical efficacy of the RA-6 beam and the BNCT treatment modality for peripheral melanomas.