The Impact of Li-Fraumeni and Germline Retinoblastoma Mutations on Leiomyosarcoma Initiation, Outcomes, and Genetic Testing Recommendations.

PURPOSE

Leiomyosarcomas (LMS) are clinically and molecularly heterogeneous, occurring mostly in sporadic but also syndromic settings. The role of pathogenic germline variants (PGV) as LMS drivers and their impact on outcomes remains uncertain.

EXPERIMENTAL DESIGN

We performed a comprehensive clinicopathologic and molecular analysis using a tumor-normal DNA next-generation sequencing assay (Memorial Sloan Kettering-Integrated Mutational Profiling of Actionable Cancer Targets) of germline-associated LMS compared with sporadic LMS.

RESULTS

Among 285 LMS [120 soft-tissue LMS (STLMS) and 165 uterine LMS (ULMS)] with germline testing, 78 (27%, 43 STLMS and 35 ULMS) cases harbored PGV, with 35/78 (45%) of PGV carriers showing biallelic inactivation of the corresponding gene in the tumor (26 STLMS and nine ULMS). The most frequent germline predispositions were TP53 (Li-Fraumeni syndrome; 17 patients, 16 in STLMS) and RB1 (retinoblastoma; 13 patients, 11 in STLMS). Germline TP53 and somatic RB1 alterations often co-occurred in the tumor andvice versa. Other biallelically inactivated PGV were enriched in DNA damage repair-related genes: CHEK2, MSH2, MSH6, RAD51D, BRCA2, and FANCA. Monoallelic PGV were mostly in ULMS and associated with co-occurring TP53 and RB1 somatic alterations. Patients with STLMS with biallelic but not monoallelic PGV were significantly younger than patients with sporadic STLMS (median ages 38 vs. 52 vs. 58 years). No differences in disease-specific or progression-free survival were observed in germline-associated versus sporadic LMS regardless of biallelic status.

CONCLUSIONS

Although patients with ULMS had a relatively low proportion of PGV, a high percentage of patients with STLMS with PGV had tumor biallelic status, indicating that PGV drive tumorigenesis in these individuals. These findings have significant implications for genetic testing recommendations.