Low-dose radiation, when applied multiple times to the whole body during several weeks, has been observed to produce a cancer therapeutic effect. The survival of cancer patients treated with low-dose radiation is similar to (Chaffey et al., 1976; Hoppe et al., 1981) or better than (Choi et al., 1979; Pollycove, 2007) the survival of patients treated with chemotherapy (see the Figures below). Since cancer patients treated with chemotherapy have better survival compared to untreated cancer patients (Huchcroft and Snodgrass, 1993), it is clear that chemotherapy has a cancer therapeutic effect. Hence, low-dose radiation applied repeatedly also has a cancer therapeutic effect and not a carcinogenic effect.
Note: Difference between the two curves is not significant.
There is also additional evidence which shows the cancer therapeutic effect of repeated applications of low-dose radiation (10 cGy or 15 cGy) to the whole body or half of the body (Mendenhall et al., 1989; Sakamoto, 2004).
These data contradict the LNT model, according to which cancer risk would be increased following exposure to low radiation doses.
Chaffey JT, Rosenthal DS, Moloney WC and Hellman S. 1976. Total body irradiation as treatment for lymphosarcoma. Int J Radiat Oncol Biol Phys 1: 399-405. http://www.ncbi.nlm.nih.gov/pubmed/823140
Choi NC, Timothy AR, Kaufman SD, Carey RW and Aisenberg AC. 1979. Low dose fractionated whole body irradiation in the treatment of advanced non-Hodgkin's lymphoma. Cancer 43: 1636-42. http://www.ncbi.nlm.nih.gov/pubmed/582159
Hoppe RT, Kushlan P, Kaplan HS, Rosenberg SA and Brown BW. 1981. The treatment of advanced stage favorable histology non-Hodgkin's lymphoma: a preliminary report of a randomized trial comparing single agent chemotherapy, combination chemotherapy, and whole body irradiation. Blood 58: 592-8. https://www.ncbi.nlm.nih.gov/pubmed/7259838
Huchcroft SA and Snodgrass T. 1993. Cancer patients who refuse treatment. Cancer Causes Control 4: 179-85. https://www.ncbi.nlm.nih.gov/pubmed/8318634
Mendenhall NP, Noyes WD and Million RR. 1989. Total body irradiation for stage II-IV non-Hodgkin's lymphoma: ten-year follow-up. J Clin Oncol 7: 67-74. https://www.ncbi.nlm.nih.gov/pubmed/2642542
Pollycove M. 2007. Radiobiological basis of low-dose irradiation in prevention and therapy of cancer. Dose Response 5: 26-38. http://www.ncbi.nlm.nih.gov/pubmed/18648556
Sakamoto K. 2004. Radiobiological basis for cancer therapy by total or half-body irradiation. Nonlinearity Biol Toxicol Med 2: 293-316. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2657505/