We found significantly more frequent expression of all eight CT antigens in ER-negative cancers, and five of them—MAGEA, CT7, NY-ESO-1, CT10 and CT45, were expressed in 12–24% of ER-negative cancers, versus 2–6% of ER-positive cancers (p<0.001 to 0.003). This evidence concerns the gene ESR1 and cancer.