Relationship between cancer cell proliferation and thallium-201 uptake in lung cancer

Although thallium-201 (Tl-201) uptake is related to perfusion in many normal tissues, the biologic rationale for Tl-201 uptake in tumors is uncertain. To determine if tumor uptake is related to cell proliferation, we correlated the relative retention of Tl-201 in lung tumors with expression of Ki-67, an indicator of cell proliferation. Methods: Sixty patients with lung tumors, included small cell carcinoma (n = 8) and non-small cell carcinoma (n = 52), underwent Tl-201 Single photon emission computed tomography (SPECT) imaging. The Tl-201 lesion uptake was determined on early and delayed images and the radiotracer retention index (RI) was calculated. Tumor specimens were obtained at surgery or bronchoscopy. The cell proliferation ratio was estimated with MIB-1, a monoclonal antibody that recognized the nuclear antigen Ki-67. Results: The average Tl-20 index was 2.13 +/- 0.61 (early) and 2.46 +/- 0.83 (delayed). The average RI was 17.44 +/- 35.01. Overall, the Tl-201 index (delayed) and the cancer cell proliferation were correlated (r = 0.70, p < 0.0001). Of interest, there was a significant correlation (r = 0.872, p < 0.0005) between the Tl-201 index on delayed images and the cell proliferation ratio in patients with small cell but not non-small cell lung carcinoma. The Tl-201 index (delayed) was significantly higher (p < 0.0001) in patients with small cell lung carcinoma than in patients with non-small cell lung carcinoma. Conclusion: Tl-201 imaging appears to be useful for evaluating patients with small cell lung carcinoma but not non-small lung carcinoma, and is correlated with the monoclonal antibody MIB-1, a marker of cell proliferation.