Assessment of treatment response in irradiated lung cancer by sequential thallium-201 SPECT: comparison with tumor volume change and survival time.
We carried out a study to evaluate treatment response and residual mass in irradiated lung cancer with single photon emission computed tomography (SPECT) using 201TI, and investigated the relation among 201TI uptake ratio, tumor volume, and patient survival time. 201TI uptake ratios and tumor volume measured before and after radiotherapy were compared in 14 patients. We divided them into a complete response (CR) group (n = 5) and partial response + no change (PR + NC) group (n = 9) according to the tumor volume response determined by CT, and a longer survival (LS) group (n = 7) and shorter survival (SS) group (n = 7) according to the survival time. The CR group showed smaller 201TI uptake ratios after irradiation (5.3 +/- 6.0%) than the PR + NC group (52.0 +/- 27.4%) (p < 0.01), but there were no significant differences in 201TI uptake ratio before irradiation or survival time in the other two groups. The LS group showed a smaller 201TI uptake ratio before (107.8 +/- 48.3%) and after (17.0 +/- 14.4%) irradiation than the SS group (126.6 +/- 34.4% p < 0.01, 52.6 +/- 27.5% p < 0.05), but there were no significant differences in tumor volume before or after irradiation in the other two groups. We concluded that 201TI SPECT is very useful to evaluate treatment response in irradiated lung cancer and can play a supplementary role in evaluating prognosis.