Background: Very high levels of ionizing radiation exposure have been associated with the development of soft-tissue sarcoma. The effects of lower levels of ionizing radiation on sarcoma development are unknown. This study addressed the role of low to moderately high levels of ionizing radiation exposure in the development of soft-tissue sarcoma.
Methods: Based on the Life Span Study cohort of Japanese atomic-bomb survivors, 80,180 individuals were prospectively assessed for the development of primary soft-tissue sarcoma. Colon dose in gray (Gy), the excess relative risk, and the excess absolute rate per Gy absorbed ionizing radiation dose were assessed. Subject demographic, age-specific, and survival parameters were evaluated.
Results: One hundred and four soft-tissue sarcomas were identified (mean colon dose = 0.18 Gy), associated with a 39% five-year survival rate. Mean ages at the time of the bombings and sarcoma diagnosis were 26.8 and 63.6 years, respectively. A linear dose-response model with an excess relative risk of 1.01 per Gy (95% confidence interval [CI]: 0.13 to 2.46; p = 0.019) and an excess absolute risk per Gy of 4.3 per 100,000 persons per year (95% CI: 1.1 to 8.9; p = 0.001) were noted in the development of soft-tissue sarcoma.
Conclusions: This is one of the largest and longest studies (fifty-six years from the time of exposure to the time of follow-up) to assess ionizing radiation effects on the development of soft-tissue sarcoma. This is the first study to suggest that lower levels of ionizing radiation may be associated with the development of soft-tissue sarcoma, with exposure of 1 Gy doubling the risk of soft-tissue sarcoma development (linear dose-response). The five-year survival rate of patients with soft-tissue sarcoma in this population was much lower than that reported elsewhere.
Level of Evidence: Prognostic Level I. See Instructions for Authors for a complete description of levels of evidence.
1Department of Orthopaedics & Traumatology, University of Hong Kong, Professorial Block, 5th Floor, 102 Pokfulam Road, Pokfulam, Hong Kong SAR, China. E-mail address: email@example.com; firstname.lastname@example.org
2National Institute of Health and Nutrition, 1-23-1 Toyama, Shinjuku-ku, 162-8636 Tokyo, Japan
3Departments of Statistics (J.C. and S.F.), Epidemiology (M.H.), Chief Scientist (K.K.), and the Institute of Radiation Epidemiology (F.K.), Radiation Effects Research Foundation, 5-2 Hijiyama Park, Minami-ku, Hiroshima-city, Hiroshima 732-0815, Japan
4Department of Radiation Oncology, Box 3085, Duke University Medical Center, Durham, NC 27710
5Department of Epidemiology, Radiation Effects Research Foundation, 8-6 Nakagawa 1-chrome, Nagasaki-city, Nagasaki 850, Japan