On the (un)effectiveness of Proton Boron Capture in Proton Therapy

TL;DR

This paper evaluates the potential of Proton Boron Capture to enhance proton therapy effectiveness, concluding that its impact is negligible at typical boron concentrations and suggesting other mechanisms are responsible for observed effects.

Contribution

The study provides detailed calculations and simulations showing Proton Boron Capture's limited role in proton therapy at realistic boron levels.

Findings

Proton Boron Capture dose is much lower than primary proton dose.

At typical boron concentrations, the reaction's impact is negligible.

Other mechanisms likely explain the decreased tumor cell survival.

Abstract

We present calculations and simulations on the role of the p+$^{11}$B$\to$3$\alpha$ reaction in proton therapy. This reaction has been recently suggested to be responsible for a decrease in the survival probability of tumor cells, when they are irradiated with low-energy protons. However, at the concentration levels typical of the proposed boron carrier (sodium borocaptate, Na$_{2}$B$_{12}$H$_{11}$SH, in short BSH), i.e. less than 100 ppm, both calculations and Monte Carlo simulations suggest that the dose related to this reaction is orders of magnitude lower than the dose delivered by the primary proton beam inside the tissues. These calculations cast some doubts on the claim of an important role played by Proton Boron Capture in enhancing the therapeutic effectiveness of proton therapy, and suggest that other mechanisms should be investigated in order to explain the observed decrease in the survival probability.