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Occurrence of other cancers in patients with chronic lymphocytic leukemia and mutations in protection of telomeres 1 (POT1) gene.

7529 Background: Mutations in POT1 gene in CLL lead to uncapping of the telomeric ends, causing fusion events and chromosomal aberrations. POT1 is mutated in approximately 4% of pts with CLL. Recent studies reported germline variants in POT1 in pts with familial CLL and in familial melanoma, cardiac angiosarcoma and glioma. We evaluated pts characteristics and the presence of other cancers (OC) in pts with CLL with POT1 mutation seen at our institution. Methods: We performed next generation sequencing (NGS)-based analysis for the detection of mutations in 29 genes frequently mutated in pts with CLL using blood and/or bone marrow samples containing a minimum of 10% clonal B-cells from 1467 pts diagnosed with CLL. Clinical characteristics, prognostic factors (FISH and IGHV status), personal and familial history of OC were collected in pts with POT1 mutations. Results: Mutations in POT1 were found in 52 of the 1467 pts studied (3.5%). Pts with POT1 mutation were young (median age 59 years), commonly presented with early stage disease (Binet stage A 69% vs B/C 31%: p=0.0046 and Rai stage 0-I 65% vs II-IV 35%; p=0.043) and predominantly male (37 male vs 15 female). According to FISH, the more frequent abnormalities were del13q (33%), no abnormalities (25%) and del11q (21%). IGHV status was more commonly unmutated (69%). The most frequent DNA mutations associated with POT1 were NOTCH1 (44%), TP53 (27%) and SF3B1 (23%). Other cancers (excluding non-melanoma skin cancer) were reported in 19 of the 52 pts with POT1 mutation (37%). The most common types were prostate cancer (12%), malignant melanoma (10%) and kidney cancer (8%). Twelve (23%) pts were diagnosed with OC before and 7 pts (13%) after the diagnosis CLL (Table). Four (8%) pts had more than one other cancer diagnoses. Twenty-eight (54%) pts had one of more first degree relatives with history of cancer. Conclusions: POT1 mutations were observed in 3.5% of pts with CLL. These pts are young and often have unmutated IGHV. We observed a high occurrence of OC, particularly malignant melanoma and kidney cancer in these pts. Additional studies are ongoing to determine the proportion of pts with germline POT1 mutation, the distribution of variant allelic frequencies and additional chromosomal abnormalities in pts with OC. Other Cancers in 52 CLL pts with POT1. [Table: see text]