Physical markers of individual radiosensitivity
In plain words
A minority of patients suffer unusually severe side effects from standard radiotherapy doses. There is no reliable test to find them in advance.
Precise statement
Identify an assay predicting severe normal-tissue reaction, defined as grade 3 or higher toxicity, before treatment, with sensitivity and specificity sufficient for clinical use. Candidate physical and cellular measures: residual DNA double-strand break foci at 24 h, chromosome aberration yield per 100 rad in lymphocytes, and apoptosis fraction after ex vivo irradiation. An answer names a validated assay with its operating characteristics.
What would settle it
Prospective blinded validation of a candidate assay against observed toxicity in a treated cohort.
Status in the literature
A lymphocyte apoptosis assay was validated prospectively for late breast fibrosis in 2015 (Azria et al., EBioMedicine), with discrimination too modest for routine clinical use.