Mechanism of 201Tl uptake in tumours

We have studied the mechanism of tumour uptake of ²⁰¹Tl by in vivo and in vitro studies. In a series of patients with breast cancer (n=26), lung cancer (n=56) and lymphoma (n=15), the time course of tumour uptake of ²⁰¹Tl paralleled that in the myocardium with almost identical times of peak uptake being obtained in tumours and myocardium. In a patient with hepatic metastases from colonic cancer undergoing laparotomy, ^99mTc labelled microspheres and ²⁰¹Tl were injected into the hepatic artery and biopsies of metastatic and normal liver tissue obtained. The tumour to normal liver activity ratios for ²⁰¹Tl were one tenth of those for ^99mTc microspheres. In the final part of the study, cells from a lung cancer tissue culture line were incubated for 30 min with ²⁰¹Tl with and without the addition of cardiac glycoside, which acts a sodium potassium pump blocker. The cells exposed to the cardiac glycoside showed markedly decreased uptake of ²⁰¹Tl compared to the cells not so exposed (0.6%±0.1% vs 11.8±0.7.2% of the administered dose). The mechanism of ²⁰¹Tl uptake of tumours is similar to that in the myocardium. Sodium potassium pump activity appears to be more important than tumour blood flow. ²⁰¹Tl uptake may provide a useful means of studying tumour viability.