We read with interest Caswell-Jin et al.’s report regarding cascade testing in relatives at-risk for hereditary cancer ( ). They noted that of 1084 first-degree relatives of individuals with a cancer predisposing pathogenic variant (PV) who underwent multigene cancer panel testing (MCPT), 4.9% tested positive for a PV in a gene other than the one present in their family. These data are important for two reasons. First, site-specific testing versus MCPT has been the standard practice, and MCPT in relatives is not recommended by national guidelines ( ). Second, although there are published reports of more than one PV identified in a family, including those identified from MCPT ( ), this is the first and largest study describing systematic use of such testing in relatives. Given that the cost of MCPT has dropped considerably ($250 or less in some US labs), it is not surprising that this testing is being offered more often—not only to index patients but also to their relatives.
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