[Usefulness of 201Tl SPECT in the evaluation of treatment effect for primary lung cancer].

Thallium-201 single photon emission computed tomography (201Tl SPECT) was performed on 20 patients with primary lung cancer before and after treatment (radiotherapy alone or combination of chemotherapy and radiotherapy). They were divided into early recurrence group and no recurrence group by presence of local tumor regrowth within 6 months after treatment. Retention index (Ret. I) after treatment was significantly lower (p < 0.005) in no recurrence group than that in early recurrence group. There were no significant differences in other items (early ratio (ER), delayed ratio (DR), and tumor size after treatment and all items before treatment). The results of this study showed that Ret. I after treatment was uniquely useful for prediction of early local recurrence of primary lung cancer. In conclusion, Ret. I after treatment in 201Tl SPECT indicated viability of residual mass, so it was useful in the evaluation of treatment effect for primary lung cancer.