In Reply to McClelland et al

To the Editor: We thank McClelland et al for their insightful comments on our study. We were also alarmed by the high stroke rate in our cohort (1). It is certainly possible that the treatment technique in our study contributed to the high stroke rate, including increased relative biological effectiveness at the distal end of the Bragg peak (2), less conformal dose distribution of older treatment delivery techniques, and perhaps other unappreciated biological differences between protons and photons.

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