Comment on `Linear energy transfer incorporated intensity modulated proton therapy optimization'

TL;DR

This paper critiques a previous study on LET-based proton therapy optimization, clarifying the mathematical inaccuracies and explaining the observed improvements in LET distribution.

Contribution

It identifies a misapplication of the Charnes-Cooper transformation in the prior work and clarifies the true nature of the proposed linear model.

Findings

The original model's linearity is based on a misunderstanding of the transformation.

The model effectively multiplies dose-averaged LET with dose, not a true linear optimization.

The observed improvements are due to this multiplicative relationship, not a linear optimization of LET.

Abstract

Cao et al (2018) published an article on inverse planning based on dose-averaged linear energy transfer (LET). Their claim that the problem can be cast as a linear optimization model relies on an incorrect application of the Charnes-Cooper transformation. In this comment we show that their linear model is simlar to one where dose-averaged LET is multiplied with dose, explaining why their model was nonetheless able to improve the LET distribution.