The irregular response to progestins directly in tumor growth might be caus
ed by dominant negative progesterone receptor (PR) mutants and the damage t
o PR-A expression, Progestin treatment as an anti-angiogenic therapy would
be less effective in the PR-mutated tumors, Therefore, various anti-angioge
nic inhibitors must be used in progestin-refractory and progestin-dependent
tumors.