FUNCTIONAL RETENTION OF TC-99M MIBI IN MEDIASTINAL LYMPHOMAS AS A PREDICTOR OF CHEMOTHERAPEUTIC RESPONSE DEMONSTRATED BY CONSECUTIVE THORACIC SPECT IMAGING

Tc-99m MIBI is used as a tumor imaging agent and has been proposed to measure p-glycoprotein function, which plays an important role in tumo r multidrug resistance to chemotherapy, It has been reported that lung cancer and breast cancer with a high retention of Tc-99m MIBI have be en more responsive to chemotherapy than tumors with low retention. Thu s Tc-99m MIBI SPECT could be used as a measure of p glycoprotein funct ion and consequently may serve as a predictor of the tumor's responsiv eness to chemotherapeutic agents. Described here are two patients with lymphomas, one with non-Hodgkin's lymphoma and the other with Hodgkin 's disease, who underwent Tc-99m MIBI thoracic SPECT before and after chemotherapy, The sequential studies demonstrated a reduction in tumor size and diminished tumor uptake in one patient and disappearance of tumor uptake after a course of chemotherapy in the other patient. The data suggest that elevated Tc-99m MIBI uptake in a tumor as a result o f retention by p glycoprotein not only demonstrates mediastinal involv ement of lymphomas but also may be used to forecast responsiveness to chemotherapy.