The decision on which cancers to treat may be based on preclinical efficacy against implantable tumors in animal models and in human tumor cell cloning assays or from hints of activity in phase I studies. In other cases, patients with tumors responsive to similar analogs will be treated with the newer drug. Other phase II studies accrue patients with common adult solid tumors who are not eligible for other treatments of known efficacy. Most phase II studies require patients to have measurable or evaluable primary tumors or metastases. Examples of lesions that do not qualify as measurable are diffuse bony metastases on bone scan, pleural effusions, patchy pulmonary infiltrates, poorly defined subcutaneous masses, and ill-defined abdominal masses.
Measurable disease is necessary to objectively define tumor response.
A complete response means the disappearance of all known sites of disease without the development of any new disease for at least one month. Patients with ill-defined sites of disease cannot be accurately evaluated according to these criteria. Evaluable disease may be measurable in one but not in two dimensions. Some studies consider any indicator of disease that can be followed serially as suitable for evaluability, including serum tumor markers and ascites. The dose and schedule for phase II studies are taken from phase I studies.