A basic research for the prediction of tumore recurrence using positron emission tomography.

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In order to develop a diagnostic method for the prediction of tumor recurrence using positron emission tomography (PET), we have performed experimental studies and clinical studies of lung cancer.Using rat tumor radiotherapy model, 11CMethionine (Met) uptake by the tumor showed sharp and rapid decrease early after radiotherapy, of which response was almost the same as that of thymidine. There are marker of proliferation. 18Ffluoroodeoxyglucose (FDG) showed slower response than that of Met or thymidine and paralleled to the expansion of necrosis, which suggested that FDG is a marker of the number of viable cells. In the process of tumor recurrence after 10 Gy irradiation, Met uptake by tumor started to increase earlier than the increase of tumor volume. Met uptake by tumor is a sensitive marker of tumor recurrence.Clinical PET studies of treatment evaluation and prediction of recurrence were performed on 21 patients of lung cancer who underwent radiotherapy. After radiotherapy, most of … More the patients had residual tumor mass. Among these, 10 patients showed no recurrence, 5 patients showed early recurrence within 4 month, and 4 patients late recurrence late the 11 months. Met-PET accurately differentiate the early recurrence from the non-recurrence, but failed to detect the late-recurrence due to the limited resolution of PET.In order to investigate the distribution of FDG within the tumor at the cellular level, we have developed a new method of microautoradiography technique. In a mouse FM3A tumor transplanted in syngeneic C3H mice, high FDG uptake was observed not only in the tumor cell but also in macrophages and young granulation tissue. Quantitative analysis suggested that about 25% of the glucose utilization was derived from non-tumore tissue in this tumor. In the second study, different dynamics of FDG uptake by each cellular element in the tumor were demonstrated. It suggested that non-neoplastic cellular elements can be differentiated from viable neoplastic cells by means of the dynamic analysis of FDG uptake. Less