To assist readers in evaluating the results of human studies of complementary and alternative medicine (CAM) treatments for cancer, the strength of the evidence (i.e., the “levels of evidence”) associated with each type of treatment is provided whenever possible. To qualify for a level of evidence analysis, a study must:

• Be published in a peer-reviewed scientific journal.
• Report on a therapeutic outcome or outcomes, such as tumor response, improvement in survival, or measured improvement in quality of life.
• Describe clinical findings in sufficient detail that a meaningful evaluation can be made.

Evidence from studies that do not meet these requirements is considered extremely weak. In addition to scoring individual studies, an overall level of evidence assessment is usually made.

Because no prospective, controlled study of the use of the Gerson therapy in cancer patients has been reported in a peer-reviewed scientific journal, no level of evidence analysis is possible for this approach. The data that are available are not sufficient to warrant claims that the Gerson therapy is effective as an adjuvant to other cancer therapies or as a cure. At this time, the use of the Gerson therapy in the treatment of cancer patients cannot be recommended outside the context of well-designed clinical trials.

Separate levels of evidence scores are assigned to qualifying human studies on the basis of statistical strength of the study design and scientific strength of the treatment outcomes (i.e., endpoints) measured. The resulting two scores are then combined to produce an overall score. For additional information about levels of evidence analysis, refer to Levels of Evidence for Human Studies of Cancer Complementary and Alternative Medicine.

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