Genetics and genomics of radiotherapy toxicity: towards prediction

Table 3 Evidence for heritability of radiosensitivity as a human trait

Study population	Assay*	Heritability (%)	Reference
16 Radiosensitive breast cancer survivors and 37 first-degree relatives, 4 breast cancer survivors with normal radiosensitivity and 15 first-degree relatives	G2	82	[41]
23 Cancer survivors, 29 partners, 38 offspring, 27 controls	G2	67	[76]
148 Monozygotic and 57 dizygotic twin pairs; 50 siblings	Apoptosis	63	[77]
199 Father, mother, offspring trios	Apoptosis	61	[78]
38 Dizygotic and 16 monozygotic twin pairs	Apoptosis; cell cycle delay	68; 59	[40]
29 Cancer survivors, 29 partners, 53 offspring	G2	58 to 78	[79]
39 Monozygotic and 10 dizygotic twin pairs	MN	68	[42]

*Peripheral blood lymphocytes were used in all studies. The G2 assay involves scoring chromosome damage in cells irradiated in G2 phase of the cell cycle. The micronucleus (MN) assay involves irradiating cells and preventing progression through mitosis. Radiation-damaged chromosomes form micronuclei that are counted.

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