Scintigraphic prediction of resistance to radiation and chemotherapy in patients with lung carcinoma: technetium 99m-tetrofosmin and thallium-201 dual single photon emission computed tomography study.

BACKGROUND. Various prognostic markers for lung carcinoma have been proposed, but to the authors' knowledge none is noninvasive and convenient for clinical use. The current study examined the utility of several radiotracers for the prediction of multidrug resistance (MDR) and radioresistance in patients with lung carcinoma. METHODS. Thirty patients with untreated lung carcinoma underwent a dual isotope single photon emission computed tomography (SPECT) scan at 10 minutes and 120 minutes after the injection of technetium-99m ( 99m Tc)-tetrofosmin ( 99m Tc-TF) (370 megabecquerels [MBq]) and thallium-201 ( 201 TlCl) (111 MBq). Retention of each tracer was evaluated semiquantitatively. Using radiation and chemotherapy (cisplatin plus etoposide), the patients either were treated sequentially (n = 12) or concurrently (n = 18). The relation between therapeutic response and retention of each tracer was analyzed. The detectability of radioresistance was examined. RESULTS. In patients treated with sequential therapy, the response to radiation was predicted by 99m Tc-TF retention, whereas 201 Tl retention was found not to be predictive. Regardless of whether the sequential or concurrent protocol was applied, 14 of 18 tumors with high 99m Tc-TF retention (≥15%) exhibited a favorable response to chemoradiotherapy whereas all 12 tumors with low 99m Tc-TF retention (≤15%) did not respond to the therapy. In contrast, 201 Tl retention was not found to be a predictive factor. CONCLUSIONS. The employed SPECT method is a useful tool for the in vivo prediction of radioresistance, P-glycoprotein (P-gp), and non-P-gp MDR in lung carcinoma. Low 99m Tc-TF retention serves as a strong predictor of therapeutic resistance. High 99m Tc-TF retention implies a favorable response. 201 Tl did not appear to be a predictive factor but is required for localization of the lesion on SPECT imaging.