Palliative Benefits of Oral Mifepristone for the Treatment of Metastatic Fibroblastic Osteosarcoma

Anticancer Res. 2021 Apr;41(4):2111-2115. doi: 10.21873/anticanres.14982.


Background/aim: It has been hypothesized that many, or even most cancers, utilize a unique immunomodulatory protein, called the progesterone induced blocking factor (PIBF) to allow spread of the cancer. Support for this concept has been provided by cancer cell line studies showing that PIBF is produced by these cancer cells and mifepristone suppresses this protein and inhibits proliferation of these cells. Furthermore, controlled murine studies with several spontaneous different types of cancer showed a clear beneficial effect of mifepristone over placebo control. Finally, there have been a variety of anecdotal reports showing efficacy of mifepristone in providing increased length and quality of life in patients with different types of advanced cancers.

Case report: Single agent mifepristone was found to provide significant palliative benefit for a 51-year-old male whose metastatic advanced fibroblastic osteosarcoma progressed despite surgery, radiotherapy, multiagent chemotherapy, and targeted therapy.

Conclusion: Thus, osteosarcoma can be added to the list of cancers, not necessarily associated with the classic nuclear progesterone receptor, that seem to respond to progesterone receptor antagonist therapy.

Keywords: Osteosarcoma; metastases; mifepristone; progesterone induced blocking factor; progesterone receptor antagonists.

Publication types

  • Case Reports

MeSH terms

  • Administration, Oral
  • Bone Neoplasms / drug therapy*
  • Bone Neoplasms / pathology
  • Cancer Pain / drug therapy
  • Humans
  • Male
  • Middle Aged
  • Mifepristone / administration & dosage*
  • Neoplasm Metastasis
  • Osteosarcoma / drug therapy*
  • Osteosarcoma / pathology
  • Palliative Care / methods*
  • Quality of Life
  • Tibia
  • Treatment Outcome


  • Mifepristone