Researchers are currently exploring the potential treatment where adding a low-cost hormone therapy to breast cancer treatment regimen could slow tumor growth in about half of women, according to a new study, released in Nature from the University of Cambridge. After treating cancer with progesterone in combination with the hormonal drug Tamoxifen. Found that tumors were half the size of those treated with just tamoxifen alone. Strong case for a clinical trial to investigate the potential benefit of adding progesterone to drugs that target the estrogen receptor.