CDKN2C -Null Leiomyosarcoma: A Novel, Genomically Distinct Class of TP53 / RB1 -Wild-Type Tumor With Frequent CIC Genomic Alterations and 1p/19q-Codeletion.

Purpose: Leiomyosarcoma (LMS) harbors frequent mutations in TP53 and RB1 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 CDKN2C at chromosome 1p32.3 (3.0% of LMS). Genomic alterations (GAs) in TP53 , RB1 , and ATRX were rare compared with the remainder of the LMS cohort (11.7% v 73.4%, 0% v 54.5%, 2.6% v 24.5%, respectively; all P < .0001). CDKN2C -null LMS patient cases were significantly enriched for GAs in CIC (40.3% v 1.4%) at 19q13.2, CDKN2A (46.8% v 7.0%), and RAD51B (16.9% v 1.7%; all P < .0001). Chromosome arm-level aneuploidy analysis of available LMS patient cases (n = 1,284) found that 81% (58 of 72) of CDKN2C -null LMS exhibited 1p/19q-codeletion, a significant enrichment compared with 5.1% in the remainder of the LMS cohort ( P < .0001). In total, 99% of CDKN2C -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: CDKN2C -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.
Competing Interests: The following represents disclosure information provided by authors of this manuscript. All relationships are considered compensated unless otherwise noted. Relationships are self-held unless noted. I = Immediate Family Member, Inst = My Institution. Relationships may not relate to the subject matter of this manuscript. For more information about ASCO's conflict of interest policy, please refer to www.asco.org/rwc or ascopubs.org/po/authors/author-center. Open Payments is a public database containing information reported by companies about payments made to US-licensed physicians (Open Payments). Erik A. WilliamsEmployment: Foundation Medicine, Inc. Stock and Other Ownership Interests: F. Hoffmann-La RocheRadwa SharafEmployment: Foundation Medicine Stock and Other Ownership Interests: RocheBrennan DeckerStock and Other Ownership Interests: Avidea Technologies Consulting or Advisory Role: Foundation Medicine, Avidea TechnologiesMeagan MontesionStock and Other Ownership Interests: RocheEthan S. SokolEmployment: Foundation Medicine Stock and Other Ownership Interests: Roche (Parent of FMI)Dean C. PavlickStock and Other Ownership Interests: RocheNikunj ShahEmployment: Foundation MedicineKevin Jon WilliamsStock and Other Ownership Interests: Hygieia, Gemphire Therapeutics Consulting or Advisory Role: Gemphire Therapeutics Research Funding: Novo NordiskJeffrey M. VenstromEmployment: Genentech, Foundation Medicine Leadership: Genentech Stock and Other Ownership Interests: Genentech Research Funding: Genentech, Roche, Foundation Medicine Travel, Accommodations, Expenses: GenentechBrian M. AlexanderEmployment: Foundation Medicine Leadership: Foundation Medicine Stock and Other Ownership Interests: Roche Research Funding: Eli Lilly (Inst), Puma (Inst), Celgene (Inst) (OPTIONAL) Open Payments Link: https://openpaymentsdata.cms.gov/physician/854258/summaryJeffrey S. RossEmployment: Foundation Medicine Leadership: Foundation Medicine Stock and Other Ownership Interests: Foundation Medicine Consulting or Advisory Role: Celsius Therapeutics Research Funding: Foundation MedicineLee A. AlbackerEmployment: Foundation Medicine Stock and Other Ownership Interests: RocheDouglas I. LinEmployment: Foundation MedicineShakti H. RamkissoonEmployment: Foundation Medicine Stock and Other Ownership Interests: Foundation MedicineJulia A. ElvinEmployment: Foundation Medicine No other potential conflicts of interest were reported.
(© 2020 by American Society of Clinical Oncology.)