UNLABELLED: 99mTc-hexakis-2-methoxyisobutyl isonitrile (MIBI) has been reported to accumulate in various tumors and to be a transport substrate for P-glycoprotein (Pgp). The aim of this study was to evaluate the usefulness of 99mTc-MIBI SPECT for in vivo assessment of lung cancer chemosensitivity. Also examined was the relationship between 99mTc-MIBI uptake and Pgp expression. METHODS: Ten lung cancer patients who had undergone surgery were examined. Before surgery, 99mTc-MIBI SPECT was performed 15 and 120 min after injection, and the early uptake (L/Ne), delayed uptake (L/Nd) and washout rate (L/Nwr) of 99mTc-MIBI were calculated by the count ratio of lesion to contralateral normal lung tissue. The results were then compared with chemosensitivity determined by the succinate dehydrogenase inhibition test using six antitumor drugs (doxorubicin, mitomycin C [MMC], vindesine, etoposide [VP-16], cyclophosphamide and cisplatin). Pgp expression was determined by immunohistochemical staining. RESULTS: Sensitivity to MMC correlated significantly with L/Ne (P < 0.01) and L/Nwr (P < 0.05). Sensitivity to VP-16 correlated weakly and insignificantly with L/Nwr. L/Nd showed no correlation with sensitivity to any drug. Neither L/Ne, L/Nd nor L/Nwr was significantly different between the Pgp-positive group (n = 2) and the Pgp-negative group (n = 8). CONCLUSION: The results suggest that 99mTc-MIBI SPECT, a noninvasive in vivo examination, can predict the chemosensitivity of lung cancer to MMC and VP-16 independently of Pgp expression.
UNLABELLED: 99mTc-hexakis-2-methoxyisobutyl isonitrile (MIBI) has been reported to accumulate in various tumors and to be a transport substrate for P-glycoprotein (Pgp). The aim of this study was to evaluate the usefulness of 99mTc-MIBI SPECT for in vivo assessment of lung cancer chemosensitivity. Also examined was the relationship between 99mTc-MIBI uptake and Pgp expression. METHODS: Ten lung cancerpatients who had undergone surgery were examined. Before surgery, 99mTc-MIBI SPECT was performed 15 and 120 min after injection, and the early uptake (L/Ne), delayed uptake (L/Nd) and washout rate (L/Nwr) of 99mTc-MIBI were calculated by the count ratio of lesion to contralateral normal lung tissue. The results were then compared with chemosensitivity determined by the succinate dehydrogenase inhibition test using six antitumor drugs (doxorubicin, mitomycin C [MMC], vindesine, etoposide [VP-16], cyclophosphamide and cisplatin). Pgp expression was determined by immunohistochemical staining. RESULTS: Sensitivity to MMC correlated significantly with L/Ne (P < 0.01) and L/Nwr (P < 0.05). Sensitivity to VP-16 correlated weakly and insignificantly with L/Nwr. L/Nd showed no correlation with sensitivity to any drug. Neither L/Ne, L/Nd nor L/Nwr was significantly different between the Pgp-positive group (n = 2) and the Pgp-negative group (n = 8). CONCLUSION: The results suggest that 99mTc-MIBI SPECT, a noninvasive in vivo examination, can predict the chemosensitivity of lung cancer to MMC and VP-16 independently of Pgp expression.