LAUSR

1512Background: Developing multiple primary cancers is an indicator of underlying hereditary cancer predisposition, but there is a paucity of data regarding the characteristics and clinical genetic testing outcome of these patients. Methods: We compared cancer index patients with 1 vs > 1 primary malignancy who underwent evaluation and clinical testing with multi-gene panels comprising up to 49 genes in a cancer genetics clinic in a tertiary cancer centre in Asia from 1998-2016. Results: Among 1191 cancer index patients, 960 (80.6%), 205 (17.2%), and 26 (2.2%) respectively had 1, 2, and ≥3 primary malignancies. Among patients with > 1 primary cancers (n = 231), the most common cancer pairs were breast-breast (35.4%), breast-ovary (12.1%), endometrium-ovary (8.2%), colon-colon (2.4%) and, colon-endometrium (2.4%). The mean age at diagnosis of the first, second and third cancers were 46.0 (21 to 87), 52.1 (21 to 89) and 57.7 (41 to 83) respectively. The mean duration between first and second cancers is 6.0 ...