What is a Placebo?
Cancer clinical trials rarely employ the use of placebos, or “sugar pills,” since participants typically suffer from a form of cancer that has resisted standard treatments and are searching for alternative, potentially effective treatments.
Clinical Cancer Trials and the Use of Placebos
Some newer anti-cancer drugs may not shrink tumors but slow tumor growth. Since testing these kinds of drugs requires control groups so researchers can determine if the drug stabilizes tumor growth, use of placebos may be necessary. Additionally, experimental drugs for cancer usually have a few side effects that are difficult to distinguish from signs of stage II, III or IV cancer, such as fatigue or decreased appetite.
Placebos should only be used in clinical trials for cancer therapies when it is scientifically and ethically appropriate and necessary. Subjects participating in cancer trials must also be informed whether they are receiving a placebo, standard treatment or experimental treatment. Finally, placebos are indicated if there is no effective treatment available, if existing treatments cause serious adverse effects or if the treatment is minimally effective.
An example of the benefits of placebo-controlled trials involves a recent phase II trial regarding efficacy of espindolol on cancer cachexia affecting patients with stage III or stage IV colorectal cancer. The s-enantiomer of pindolol, espindolol exerts antagonist/agonist activity at the β1, β2, β3 and 5HT1A receptors. Preclinical models have shown espindolol to produce anti-catabolic and pro-anabolic effects on fat mass and muscle. In this particular trial, espindolol significantly improved subjects’ fat free mass, reversed weight loss progression and maintained fat mass for subjects suffering non-small cell lung cancer-related cachexia or advanced colorectal cancer. Use of a placebo allowed researchers to determine that the most beneficial effects occurred between placebo dosage and high dosage of espindolol, suggesting espindolol effects correlate with dose response.
Implications of the Placebo Effect in Cancer Clinical Trials
The placebo effect is a physiological and psychological response experienced by people suffering a wide variety of health issues. An example of the placebo effect might involve a lung cancer patient recently diagnosed with stage III lung cancer. After receiving standard therapies, the patient’s cancer continues to progress, obviously resistant to these treatments.
The patient’s oncologist informs the patient he has about six months to live. In a desperate attempt to help his patient, the doctor gives the patient a bottle of placebo pills and tells him the pills are a new and effective cancer medication just released in Europe but not yet approved by the FDA. The patient takes the pills as instructed. Within two months, the doctor discovers his patient’s condition has improved and his lung cancer growth has slowed considerably.
Although this is a hypothetical scenario, implications of clinical trial results impacted by the placebo effect could be devastating for the future of any experimental cancer therapy. Comparing the benefits of an experimental drug to the benefits of a placebo could essentially negate the potential of an experimental cancer therapy to be approved by the FDA and marketed in the U.S.
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