Other limitations of our study were that 3H-FLT was used instead of 18F-FLT and only one tumor model (A431) was used to compare the uptake of 3H-fluorothymidine with the uptake of 18F-FDG, Ki67 and phospho-EGFR after the treatment with two different doses of gefitinib. The gene discussed is MKI67; the disease is neoplasm.