Besides evaluating cancer treatment, some clinical trials evaluate supportive care for cancer patients or assess methods of either preventing cancer or detecting it at an early stage, when treatment is often more effective. Toxicities associated with Group C drugs are generally manageable at local hospitals, and the drug is provided by the NCI to any qualified oncologist with an eligible patient. Occasionally, administration of a Group C drug requires specialized supportive care, so the drug is provided only to oncologists at specified Cancer Centers and the protocol is called a modified Group C protocol. TRC protocols are a limited mechanism by which treatment on a clinical trial is provided at the NCI Clinical Center or at NCI-funded Cancer Centers to patients for whom no standard treatments are available and who do not qualify for existing clinical trials. Study designs Clinical trials are designed to answer questions concerning the safety and efficacy of treatment with statistical validity, particularly in phase III studies where the issue of replacing or augmenting accepted therapies or developing effective interventions to prevent cancer is at stake.
Randomization is used to ensure an unbiased assignment to treatment.
To more carefully balance the patient populations randomized to each arm, studies are usually stratified by factors known or expected to affect outcome. Published reports of randomized clinical trials are used in the PDQ treatment statements whenever possible to support the inclusion of a treatment regimen. Sometimes phase II studies are stratified to assure a balance in patient entry despite limited accrual. Some clinical trials with multiple regimens have a crossover design to allow patients who are not responding to their originally assigned treatment to try the other treatment. Organizations conducting clinical trials Clinical trials are conducted by cooperative groups, cancer centers, and individual institutions and may be funded by the NCI, drug companies, and other interested groups.