Unusual course of disease and genetic profile in Li-Fraumeni syndrome-associated osteosarcoma - a case report.

Background: Osteosarcoma is a highly malignant tumour associated with numerous and complex genetic alterations like copy number alterations. Recent whole genome studies revealed distinct mutations in several candidate oncogenes. While clinical parameters stratify osteosarcoma patients in risk groups, genetic profiles have not yet been used to tailor tumour treatment. However, specific copy number alterations seem to have a prognostic impact in osteosarcoma treatment. Somatic TP53 gene mutation frequently occurs in sporadic osteosarcoma. When arising germline, TP53 mutation leads to Li-Fraumeni syndrome and may result in early life osteosarcoma. The effect of Li-Fraumeni syndrome on the genetic profile of osteosarcoma and the consideration of the syndrome during cancer treatment are topics of current research.

Case Presentation: We report a 25-year-old female with pelvic osteosarcoma refusing continuation of therapy. She interrupted neo-adjuvant chemotherapy according to EURAMOS-1/COSS recommendations and declined local or further adjuvant therapy. Surprisingly, she remained in sustained remission for the osteosarcoma but eventually died from newly diagnosed breast cancer. After establishment of breast cancer, we detected TP53 germline mutation and investigated the osteosarcoma material with array-CGH.

Conclusion: Genetic examination of the tumour evidenced several copy number alterations with striking differences to previously reported data. We discuss possible influences of the genetic profile on the unusual clinical course and the significance of Li-Fraumeni syndrome for the genetic profile. Specific loss of (proto-) oncogenes might have contributed to the unusual case. Further large-scale genetics of Li-Fraumeni patients combined with detailed clinical data will help to identify specific genetic risk profiles and improve treatment.