Bone marrow regeneration and extension after extended field irradiation in Hodgkin's disease

The dose response data for bone marrow suppression, following localized irradiation as recorded in the literature, are 3,000 rads. Since doses from 3,500 rads to 4,500 rads are widely utilized in extended field irradiation, the probability of ablation of a major portion of the bone marrow compartment exists with the current techniques of treatment for Hodgkin's disease. The ability of geographically mapping bone marrow distribution in a semiquantitative fashion is possible with modern radioisotope scanning procedures. 99mTc‐S colloid activity parallels 59Fe and can be used to reflect hematopoietic activity although a disparity between the RES and erythron compartments has been reported. Clinical evidence utilizing 99mTc‐S colloid bone marrow scanning techniques indicates that prolonged suppression of bone marrow occurs immediately following completion of segmental sequential irradiation in patients with Hodgkin's disease and persists for a period of 1 or 2 years. New evidence is presented of partial to complete bone marrow regeneration at 4,000 rads range in 85% of the exposed bone marrow sites at 2 years if the doses are fractionated. Mechanisms of bone marrow recovery which are discussed include: increased hematopoietic production in shielded marrow sites, expansion of bone marrow space, and infield regeneration of bone marrow.