The Long-Term Success of Local Radiation Therapy in Preventing Tumor Regrowth in the Treated Field

Abstract

The local tumor regrowth rate for patients irradiated at the Massachusetts General Hospital from 1973 to 1979 was evaluated by the cumulative frequency of local tumor regrowth. The results indicate that following 6,800–7,500 cGy of external beam irradiation, the absence of tumor regrowth in the treated field for patients with Stage T₂ (B) tumors occurs in 85 to 90 percent. This curve, relating the cumulative incidence of local tumor regrowth against time, approached an asymptote after 5 to 7 years, suggesting there may be no further instances of local tumor regrowth with “infinite” time of follow up. In contradistinction were the 122 patients with clinical Stage T₃ and T₄ (C) tumors whose cumulative incidence of regrowth curve appears to be still rising from 6 to 10 years, suggesting that 35 percent of patients will have had regrowth by 10 years, and that this may increase with further time of follow up. The incidence of local tumor regrowth rate for patients with Stage T₂ tumors (less than 10 percent at 8 years) is significantly lower than that for patients with Stage T₃ and T₄ tumors (35 percent at 8 years) at the p = 0.0024 level.