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

Although thallium-201 (Tl-201) uptake is related to perfusion in many norma l tissues, the biologic rationale for Tl-201 uptake in tumors is uncertain. To determine if tumor uptake is related to cell proliferation, we correlat ed the relative retention of Tl-201 in lung tumors with expression of Ki-67 , an indicator of cell proliferation. Methods: Sixty patients with lung tum ors, 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 image s 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 ant igen 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 T l-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-smal l cell lung carcinoma. Conclusion: Tl-201 imaging appears to be useful for evaluating patients with small cell lung carcinoma but not non-small lung c arcinoma, and is correlated with the monoclonal antibody MIB-1, a marker of cell proliferation.