Sirolimus and Cyclophosphamide in Metastatic or Unresectable Myxoid Liposarcoma and Chondrosarcoma

Inclusion Criteria: * Pathologically proven conventional chondrosarcoma * Or pathologically proven myxoid liposarcoma with PIK3CA mutation or Phosphatase and tensin homolog (PTEN) loss * Or pathologically proven mesenchymal or dedifferentiated chondrosarcoma * Patient is 18 years and up * Documented radiographic progression of disease according to RECIST 1.1 criteria in last 6 months * Written signed informed consent * Adequate bone marrow function (Hb ≥ 6.0 mmol/L, absolute neutrophil count ≥ 1.5 x 109/L, platelets ≥ 80 x 109/L) * Availability of archival tumor material for central review or be able to perform a 3 core fresh biopsy * Ability to adhere to the study visits and all protocol requirements Exclusion Criteria: * Previously treated with an mTOR inhibitor * Known to be allergic to cyclophosphamide * Life expectancy of less than 3 months * No measurable lesions according to RECIST 1.1 * Eastern cooperative oncology group (ECOG) Performance status \>2 * Major surgery less than 4 weeks prior to start of treatment * Known human immunodeficiency virus (HIV) positivity * A decreased renal function with calculated glomerular filtration rate (GFR) \< 30ml/min * Systemic anti-cancer therapy within 28 days prior to the first dose of study drug , or radiotherapy to a target lesion within 21 days prior to the first dose of study drug * Pregnant or lactating women * Other invasive malignancies diagnosed within the last 5 years, except non-melanoma skin cancer and localised cured prostate and cervical cancer