1999 年 19 巻 1 号 p. 37-47
Strategy for treatment of cancer by heavy ions beam, i. e., dose per fraction, total dose were discussed in this study. The survival curves from cell studies can be fitted to linear quadratic model, a nd survivingf ractionc an b e. calculateda t any doses. The simplem odel of fractionation makes linear survival curves as a function of number of fractions. The final surviving fraction after numberso f fractionsc an be calculateda t the final fraction. An approximaten umber of cells can be calculatedb y an averages ize of cells. To obtain “ cure”, tumor cells must be eradicated up to even the last cell, i. e., ∼1 X 10-10will be necessary to achieve “cure”. The fractionated calculationo f survivala fter 30th(the final) fraction of a conventional X-ray therapy for a resistant tumor cells showed only 0.0001, indicating far from the cure. Survivals after heavy ion beam were estimatedb y the same model, fitting survivalc urves of resistant cells against heavy ions. The results showedu singa ppropriated ose per fraction, t he final survivingf ractionr eached to a possible curability level. This study shows that the model using survival curves is a simple way to imagineh ow the radiationb eam eradicatest umor, a nd it wouldb e effectivet o help to be integrated into treatment planning.