Rapid progression of metastatic osteosarcoma after initiation of a reduced-intensity conditioning regimen with immunosuppressive fludarabine.

Indications for RIST have not been established in patients with solid tumors. In this study, we performed RIST as immunotherapy in a 13-yr-old girl with intractable but not progressive osteosarcoma, which originated from the inter-costal region. Carcinomatous pleurisy suddenly developed after the start of a conditioning regimen that included Flu and BUS. She died of respiratory failure on day +19 without signs of engraftment. This case suggests that unexpected acceleration of tumor growth may occur following RIST with immunosuppressive drugs before the development of a beneficial GVT effect.