CD34-positive cell yield in peripheral blood of cancer patients during radiation therapy

For the purpose of evaluating the feasibility of inducing CD34-positive cells in peripheral blood by radiation therapy, we examined the changes in CD34-positive cells in 21 cancer patients (16 with lung cancer and five with esophageal cancer) during thoracic radiotherapy using flow cytometry and CD34 monoclonal antibody. Although assays of granulocyte-colony-forming units (G-CFU) and granulocyte-monocyte-colony-forming units (GM-CFU) were also performed for 16 of the patients during radiation therapy, in most of these cases there was approximately one G-CFU or GM-CFU for every 100 CD34-positive cells. Seven of the 21 cancer patients showed percentages of CD34-positive cells of more than 3% (more than mean + 2 S.D.; standard deviation) of mononuclear cells in peripheral blood in at least one of the examinations. However, six of these seven patients were in stage IV with distant metastases (four with lung cancer and two with esophageal cancer), and another lung cancer patient was in stage III. Therefore, CD-34 positive cells were shown to appear in peripheral blood especially in the patients with advanced stages of malignancy, and further examinations are needed to induce CD34-positive cells by radiation therapy for possible application of ultra-high dose chemotherapy supported by peripheral blood stem cell transplantation.