-Null Leiomyosarcoma: A Novel, Genomically Distinct Class of /-Wild-Type Tumor With Frequent Genomic Alterations and 1p/19q-Codeletion.

PURPOSE

Leiomyosarcoma (LMS) harbors frequent mutations in and but few actionable genomic alterations. Here, we searched for recurrent actionable genomic alterations in LMS that occur in the absence of common untreatable oncogenic drivers.

METHODS

Tissues from 276,645 unique advanced cancers, including 2,570 uterine and soft tissue LMS, were sequenced by hybrid-capture-based next-generation DNA and RNA sequencing/comprehensive genomic profiling of up to 406 genes. We characterized clinicopathologic features of relevant patient cases.

RESULTS

Overall, 77 LMS exhibited homozygous copy loss of at chromosome 1p32.3 (3.0% of LMS). Genomic alterations (GAs) in , , and were rare compared with the remainder of the LMS cohort (11.7% 73.4%, 0% 54.5%, 2.6% 24.5%, respectively; all < .0001). -null LMS patient cases were significantly enriched for GAs in (40.3% 1.4%) at 19q13.2, (46.8% 7.0%), and (16.9% 1.7%; all < .0001). Chromosome arm-level aneuploidy analysis of available LMS patient cases (n = 1,284) found that 81% (58 of 72) of -null LMS exhibited 1p/19q-codeletion, a significant enrichment compared with 5.1% in the remainder of the LMS cohort ( < .0001). In total, 99% of -null LMS were in women; the median age was 61 years at surgery (range, 36-81 years). Fifty-five patient cases were uterine primary, four were nonuterine, and the remaining 18 were of uncertain primary site. Sixty percent of cases showed at least focal epithelioid variant histology. Most patients had advanced-stage disease, with 62% of confirmed uterine primary LMS at International Federation of Gynecology and Obstetrics stage IVB. We further validated our findings in two publicly available datasets: The Cancer Genome Atlas and the Project GENIE initiative.

CONCLUSION

-null LMS defines a genomically distinct tumor that may have prognostic and/or therapeutic clinical implications, including possible use of specific cyclin-dependent kinase inhibitors.