Key result
Radiation-associated breast angiosarcomas demonstrated frequent mutations in the BRCA1 DNA damage response pathway and a distinct ionizing radiation mutational signature characterized by C→T substitutions.
Observational (n=16)
No
Radiation-associated breast angiosarcomas exhibit a distinct mutational pattern enriched in DNA repair genes (e.g., BRCA1 pathway) and a characteristic IR signature, suggesting potential new targeted treatment strategies.
May inform BRCA1-targeted therapy trials in radiation-associated breast angiosarcoma; hypothesis-generating and requires prospective validation.
// Bryan J. Thibodeau 1 , Vincent Lavergne 2 , Nayana Dekhne 3 , Pamela Benitez 3 , Mitual Amin 4 , Samreen Ahmed 1 , Jean L. Nakamura 2 , Philip R. Davidson 5 , Alice O. Nakamura 5 , Inga S. Grills 6 , Peter Y. Chen 6 , Jessica Wobb 6 and George D. Wilson 1, 6 1 Beaumont BioBank, Beaumont Health, Royal Oak, MI, USA 2 Department of Radiation Oncology, University of California, San Francisco, CA, USA 3 Department of Surgery, Beaumont Health, Royal Oak, MI, USA 4 Department of Pathology, Beaumont Health, Royal Oak, MI, USA 5 Department of Finance and Statistical Analysis, University of Alberta, Edmonton, Alberta, Canada 6 Department of Radiation Oncology, Beaumont Health, Royal Oak, MI, USA Correspondence to: George D. Wilson, email: george.wilson@beaumont.edu Keywords: angiosarcoma; radiation-associated; breast; mutational signature; next generation sequencing Received: September 15, 2017 Accepted: October 13, 2017 Published: January 19, 2018 ABSTRACT Purpose: Radiation-associated breast angiosarcomas are a rare complication of radiation therapy for breast carcinoma. With relatively little is known about the genetic abnormalities present in these secondary tumors, we examined genomic variation in biospecimens from radiation-associated breast angiosarcomas. Experimental Design: Patients were identified that had a previous breast cancer diagnosis, received radiation therapy, and developed angiosarcoma in the ipsilateral breast as the earlier cancer. Tumor regions were isolated from archival blocks using subsequent laser capture microdissection. Next generation sequencing was performed using a targeted panel of 160 cancer-related genes. Genomic variants were identified for mutation and trinucleotide-based mutational signature analysis. Results: 44 variants in 34 genes were found in more than two thirds of the cases; this included 12 variants identified as potentially deleterious. Of particular note, the BRCA1 DNA damage response pathway was highly enriched with genetic variation. In a comparison to local recurrences, 14 variants in 11 genes were present in both the primary and recurrent lesions including variants in genes associated with the DNA damage response machinery. Furthermore, the mutational signature analysis shows that a previously defined IR signature is present in almost all of the current samples characterized by predominantly C→T substitutions. Conclusions: While radiation-associated breast angiosarcomas are relatively uncommon, their prognosis is very poor. These data demonstrate a mutational pattern associated with genes involved in DNA repair. While important in revealing the biology behind these tumors, it may also suggest new treatment strategies that will prove successful.
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Thibodeau et al. (2018) conducted an observational in Radiation-associated breast angiosarcoma (n=16). Prior radiation therapy vs. Sporadic angiosarcoma was evaluated on Genomic variants and trinucleotide-based mutational signatures. Radiation-associated breast angiosarcomas demonstrated frequent mutations in the BRCA1 DNA damage response pathway and a distinct ionizing radiation mutational signature characterized by C→T substitutions.
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