Bone marrow recovery after irradiation of the spine

Background: Imaging of bone marrow by radio labeled antibodies against NCA- 95 antigen of human granulocytes offers the possibility to visualize granul opoietic activity. After radiotherapy, a reduced uptake delineates the radi ation field. Aim of our investigation was the study of strength and duratio n of this effect. Patients and Methods: We analyzed 80 cases of patients irradiated for diffe rent primary or metastatic malignancies including parts of the spine who re ceived a bone marrow scan for re-staging or during follow-up. Activity upta ke of vertebrae inside and outside the irradiation portal was evaluated by ROI and the ratio was taken as measure of bone marrow suppression. Results: A depression of granulopoietic bone marrow activity was seen even after a few fractions of 1.8 or 2 Gy (Figure 1). Depending on time since ir radiation (Figure 2), we found a bone marrow recovery. In patients without bone metastasis, regeneration could be complete, whereas in patients treate d for metastases, it was incomplete in all cases (Figure 3). Conclusions: For a certain time after irradiation, radioimmunoimaging delin eates the irradiation portal by showing depression of granulopoiesis. Later on, it also shows bone marrow regeneration after radiotherapy. This may be helpful in reconstruction of radiation portals or in toxicity estimation d uring multimodal cancer therapy.