SEMIQUANTITATIVE ASSESSMENT OF TC-99(M)-SESTAMIBI UPTAKE IN LUNG-CANCER - RELATIONSHIP WITH CLINICAL-RESPONSE TO CHEMOTHERAPY

The objectives of this study were to measure semi-quantitatively uptak e of Tc-99(m)-sestamibi (Tc-99(m)-MIBI) by tumour tissue in patients w ith lung cancer and to investigate its relationship with clinical resp onse to chemotherapy. Tc-99(m)-MIBI single photon emission tomography was performed at the time of diagnosis in 31 patients with biopsy-prov en lung cancer (19 small cell carcinomas, 12 non-small cell carcinomas ), all of whom were undergoing chemotherapy. Fifteen patients were als o investigated 2 weeks after the first and third cycles of chemotherap y. To quantify Tc-99(m)-MIBI uptake, a tumour/lung (T/L) ratio was cal culated for the tomographic slices. The response to chemotherapy was r ated as complete remission, partial remission or no remission using di mensional criteria. The results were expressed as the median and inter quartile range; non-parametric statistical analyses were used. Forty-o ne neoplastic localizations (31 primary tumours and 10 hilar or medias tinal lymph node masses) were assessed. The median T/L ratio of the pr imary tumours was 1.85 (range 1.7-2.4). Patients with a different resp onse to chemotherapy had a significantly different median T/L ratio be fore chemotherapy: complete remission (n = 8), T/L ratio = 2.95 (range 2.20-3.25); partial remission (n = 10), 2.15 (range 1.77-2.40); no re mission (n = 13), 1.70 (range 1.47-1.75) (Kruskal-Wallis, P<0.0001). A T/L ratio of 1.80 gave sensitivity of 83%, specificity of 85% and acc uracy of 84% in the prediction of the response to chemotherapy. The pa tients with small cell carcinomas demonstrated greater Tc-99(m)-MIBI u ptake than those with non-small cell carcinomas: T/L ratio, median 2.3 0 (range 1.76-3.00) vs 1.70 (range 1.50-1.78) (Mann-Whitney U-test, P = 0.001). No significant difference in Tc-99(m)-MIBI uptake was observ ed between the 10 lymph node metastases and the corresponding primary tumours: T/L ratio, median 2.30 (range 1.75-2.50) vs 2.15 (1.77-3.00) (Wilcoxon's paired samples rank test, N. S.). Of the 15 patients who w ere monitored with scintigraphy during chemotherapy, 10 showed complet e or partial remission and a parallel reduction in their T/L ratio. Th e other five patients showed no response to chemotherapy and their T/L ratio was either unaffected or increased. We conclude that the semi-q uantitative assessment of Tc-99(m)-MIBI uptake may have a significant role to play in the management of lung cancer, providing an effective means of predicting the efficacy of chemotherapy and of selecting subg roups of patients requiring radiotherapy or combined protocols before the start of treatment. Tc-99(m)-MIBI imaging may also be of use in mo nitoring clinical response to chemotherapy.