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Vitamin A, N-acetylcysteine do not prolong survival of cancer patients
WESTPORT, Jun 21 (Reuters Health) - Supplementation with Vitamin A and/or N-acetylcysteine in patients with head and neck or lung cancer has no apparent benefit in terms of survival or tumor recurrence in the upper and lower airways, according to long-awaited results from a large randomized trial in Europe.
Dr. Nico van Zandwijk, of The Netherlands Cancer Institute in Amsterdam, and colleagues from the European Organization for Research and Treatment of Cancer Head and Neck and Lung Cancer Cooperative Groups report the findings of the trial, dubbed EUROSCAN, in the June 21st issue of the Journal of the National Cancer Institute.
Previous smaller trials had suggested that the retinoids 13-cis-retinoic acid and vitamin A protect against secondary cancers in patients with head and neck or lung cancer, but large randomized trials of vitamin A and beta-carotene in smokers failed to show a protective effect, the research team notes.
Vitamin A and the antioxidant N-acetylcysteine have different mechanisms of action. To see if these compounds could prevent secondary cancers, Dr. van Zandwijk and colleagues recruited 2,592 patients with head and neck or lung cancer, most of whom smoked or had a history of smoking. The patients were randomized to daily doses of vitamin A, N-acetylcysteine, both compounds, or no treatment for 2 years.
The researchers explains that they decided not to incorporate a placebo into the study design due to cost, and because of the odor and side effects of vitamin A and N-acetylcysteine.
After a median follow-up of 49 months, the results showed that neither vitamin A nor N-acetylcysteine supplementation, alone or together, had any significant effect on overall survival or event-free survival. This finding held true when patients with head and neck cancer and patients with lung cancer were analyzed separately.
Dr. van Zandwijk's group suggests that perhaps potential chemopreventive agents should be guided through phase I and phase II studies before large randomized trials are initiated, and that subjects in cancer prevention trials, including EUROSCAN, should be followed for at least 10 years before definite conclusions are reached, given that cancer development is a multistep process.
In an editorial, Dr. Gilbert S. Omenn, of the University of Michigan in Ann Arbor, writes that although "chemoprevention of lung cancer is proving difficult and frustrating," retinoids remain one of the most promising classes of agents. "It is plausible that 13-cis-retinoic acid, 9-cis-retinoic acid, and even retinyl palmitate [vitamin A] may be effective in yet-to-be-defined subgroups of patients," he points out. |
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