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.Osteosarcoma is a less common cancer accounting for less than 1% of all cancers (1). It is most common in early puberty, or patients aged 50-70 (2). Though it is most commonly found in long bones, including the femur, tibia, and humerus, it can also be found in the pelvis (3).Unfortunately, once the osteosarcoma has been diagnosed, it is likely that it has already metastasized, especially to the lungs, which leads to a median time of progression of 10 months when radiographic evidence of lung lesions appears (4, 5). Thus, the modern concept of treatment for osteosarcoma, except possibly low-grade lesions, includes neoadjuvant therapy with doxorubicin, cisplatin, and high dose methotrexate, followed by surgical resection of the osteosarcoma. Subsequent to surgical resection, adjuvant chemotherapy is recommended.Wide surgical resection, or limb amputation, are the types of surgical techniques performed. There are various factors that help the surgical oncologist determine which type of procedure to perform (6, 7). It seems that the majority of surgeons at present perform the technique of wide excision, with limb sparing surgery, as opposed to amputation (7).Regarding adjuvant chemotherapy, there have been several clinical trials evaluating the efficacy of tyrosine kinase inhibitors, which are considered as multi-target drugs. Both oral multi kinase inhibiting drugs, regorafenib and pazopanib, are being used in clinical trials for osteosarcoma (8-10). Regorafenib targets angiogenic factors (VEGFR1-3, TIE2) and oncogenic kinases (KIT, RET, RAF). Pazopanib inhibits VEGFR, PDGFR, and cKIT.One of the major developments in the treatment of a variety of cancers is immunotherapy, where antibodies are developed against key factors needed for tumor progression, and especially against factors that allow the cancer to evade...