Preclinical studies have shown that IGF-1R expression can be upregulated by estrogen and downregulated by tamoxifen.[10–13] Moreover, a clinical study in patients who received adjuvant treatment with tamoxifen showed a decrease in IGF-1R expression in tamoxifen-resistant recurrences compared to the primary tumor.[14] IGF-1R may also play a role in resistance to several types of treatment. The gene discussed is IGF1R; the disease is neoplasm.