What is your preferred skin surface maximum dose constraint for skin brachytherapy?

In a recently published study of electronic skin surface brachytherapy, we used a technique that delivered approximately 8.7 Gy per fraction to skin surface (125% of the prescribed dose of 42 Gy in 6 fractions of 7 Gy delivered to 3 mm depth from skin surface). This publication demonstrates the acute toxicities of that approach well: Kuo et al., PMID 36586493.

A survey of skin brachytherapists reported on doses to the skin surface. It reported, "Maximum allowable dose to skin ranged between 125% ...