<b>"Certain [sarcoma] subtypes have virtually no chance of major clinical response to conventional cytotoxic therapies, so whenever possible, these patients should be offered treatment with promising new agents in clinical trials. Included in this category of sarcomas with primary chemotherapy resistance would be most non-uterine leiomyosarcomas."</b> [Singer, S, Demetri, GD, Baldini, EH, Fletcher, CDM.  "Management of Soft-tissue sarcomas: An Overview and Update". Lancet Oncology. Oct 2000]

Clinical trials used to develop new anti-cancer agents are labeled as phase I, phase II, phase III and phase IV. Such trials are often performed in patients with metastatic cancer. 

<b>Phase I</b> trials are conducted in small numbers of patients to determine a drug's maximally tolerated dose and toxicity/side effect profile. 

In <b>phase II</b> studies, the anti-tumor activity of the new agent is tested in different tumor types. 

If a drug is found to be promising in phase II studies, in <b>phase III</b> studies it is then compared to standard therapy [randomized trial design]. 

In <b>phase IV</b> studies, the effectiveness and safety of the drug are tested in a standard clinical setting. 

In oncology, <b>phase II</b> studies are also used to evaluate new combinations of previously approved agents.

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