Despite its relatively low ranking based on marker score, CA9 was selected for further investigation due to an availability of high affinity inhibitors for imaging [49–51] and its general applicability among several cancer types, in addition to lung cancer, including cancers of the brain, breast, cervix, colon, head and neck, kidney, ovaries, and pancreas [25, 35, 81–83]. Here, CA9 is linked to lung cancer.