Radiation-induced sarcoma (RIS) can originate in either the irradiated bone or soft tissues after a period of latency. They are usually high-grade tumours with a poor prognosis when compared with primary sarcomas. Malignant fibrous histiocytoma and osteosarcoma are the two most common histological types.
The incidence is not well known as it is related theoretically to all radiation therapy procedures 1. One study in Finland taking in consideration all treated parts of the body found a risk of 0.05% 2. RIS constitutes ~4% of all sarcomas 3.
It was found a higher risk of RIS among younger patients; it has been thought a link between a particular cancer type that is more common among the young 2. There is a direct correlation with the risk and the radiation doses 4.
A history of prior radiation therapy is mandatory for a diagnosis of RIS to be made. The median latency period is around 14 years 4, however RIS can develop in a short time as 3-4 years following radiotherapy.
Treatment and prognosis
RIS has a poor prognosis compared to primary sarcomas: the 5-year survival rates vary from 17 to 58% in RIS compared with 54–76% in patients with sporadic sarcomas. Some unfavourable factors related to RIS are: central tumour site, incomplete surgical remission, microscopic tumour necrosis and the presence of metastases, the two former factors overrepresented in RIS 3.
Similar to primary sarcomas, RIS originating soft-tissues has on tumour size and grade the two most important prognostic factors 1:
- high-grade tumours larger than 5 cm: usually treated with primary chemotherapy followed by a margin-negative surgical excision of the residual disease
- low-grade tumours and high-grade tumours with 5 cm or smaller: usually treated with a margin-negative surgical excision and systemic chemotherapy is considered when a negative margin is not certain
RIS originating in bone is usually approached with primary chemotherapy followed by a margin-negative excision 1.
History and etymology
RIS was first described in 1920’s in workers painting radium watch dials 4.
- 1. Patel SR. Radiation-induced sarcoma. Curr Treat Options Oncol. 2002;1 (3): 258-61. Pubmed citation
- 2. Virtanen A, Pukkala E, Auvinen A. Incidence of bone and soft tissue sarcoma after radiotherapy: a cohort study of 295,712 Finnish cancer patients. Int. J. Cancer. 2006;118 (4): 1017-21. doi:10.1002/ijc.21456 - Pubmed citation
- 3. Bjerkehagen B, Småstuen MC, Hall KS et-al. Why do patients with radiation-induced sarcomas have a poor sarcoma-related survival?. Br. J. Cancer.106 (2): 297-306. doi:doi:10.1038/bjc.2011.559 - Free text at pubmed - Pubmed citation
- 4. Perez and Brady's Principles and Practice of Radiation Oncology. LWW. (2008) ISBN:078176369X. Read it at Google Books - Find it at Amazon