Potential Applications of the Compact Fast-neutron Generator for the Adjuvant Treatment of Solid Tumours with the Intra-operative Radiotherapy (nIORT®) Technique: Simulation and Dosimetry Analyses with the MCNP Code
DOI:
https://doi.org/10.14738/bjhr.1304.12052Abstract
The potentiality of the intraoperative radiotherapy (IORT) with fast neutrons as an adjuvant treatment for severe solid cancers has been investigated in a 5-year research program. The therapeutic dose is administered by a single irradiation directly within the surgical cavity after surgical resection by means of a compact neutron generator (CNG) with the so-called neutron-IORT technique patented as nIORT®. Two CNG prototypes – exploiting the deuterium–deuterium fusion reaction to produce neutrons of 2.45 MeV energy - are currently undergoing experimental characterisation with the main objectives of demonstrating: - the therapeutic effectiveness of fast neutrons, having a relative biological effectiveness (RBE) ≈ 3÷4 times greater than that of standard RT treatments with X-rays and electrons, and low sensitivity to hypoxia; - the feasibility of installing the CNG - surrounded by ~1 m cube shield - in a hospital operating room dedicated to nIORT® treatments, without posing safety and environmental concerns. In parallel, several dosimetry analyses have been conducted using the MCNP Monte Carlo code by a detailed modelling of the CNG equipped with cylindrical and hemispherical nIORT® applicators positioned within brain and breast surgical cavities, respectively. Thanks to the high neutron flux (~10⁸ cm⁻² s⁻¹) and leveraging on the high RBE of fast neutrons, the MCNP simulations indicate that dose targets of ~10 Gy(RBE) could be administered in ~10÷20 minutes only. Moreover, the diffuse neutron beam may enable: the treatment of large and topographically irregular tumour beds, which remain challenging targets for the focused beams employed in standard RT and IORT techniques; the irradiation of the tumour bed margins - typically infiltrated by quiescent cancer cells and locale recurrences - thereby potentially enhancing the local tumour control; a limited damage and adverse effects to the nearest organs at risk, due to the limited penetration of neutrons over few centimetres in the biological tissues; to integrate the nIORT® adjuvant treatment for radioresistant tumours with local recurrences in a multimodal approach integrating surgery, chemotherapy and/or immunotherapy. In memory of Marina Gherardi, Marika de Feo and Gianluca Costamagna
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