Prévention des seconds cancers primaires par supplémentation vitaminique chez les patients traités pour un cancer ORL

Antioxidant vitamins and chemoprevention

Free radicals play an important role in human carcinogenesis and the mechanism of their counteraction by antioxidant vitamins has been reviewed. It seems more likely that these vitamins work in concert rather than acting singly. Currently available data are compatible with the notion that these vitamins act as chemopreventives against some important cancers, e.g. carotenoids for lung cancer, ascorbic acid for salivary gland cancer, tocopherols for head and neck cancers etc. Thus, a greater consumption of fruits and vegetables should be encouraged as they are the natural sources of these chemopreventive, antioxidants along with other protective factors packaged by nature. However, much work still remains to be done to establish the role of antioxidant vitamins in carcinogenesis.

Randomized trial of antioxidant vitamins to prevent acute adverse effects of radiation therapy in head and neck cancer patients

PURPOSE

Many cancer patients take antioxidant vitamin supplements with the hope of improving the outcome of conventional therapies and of reducing the adverse effects of these treatments. A randomized trial was conducted to determine whether supplementation with antioxidant vitamins could reduce the occurrence and severity of acute adverse effects of radiation therapy and improve quality of life without compromising treatment efficacy.

PATIENTS AND METHODS

We conducted a randomized, double-blind, placebo-controlled trial among 540 head and neck cancer patients treated with radiation therapy. Patients were randomly assigned into two arms. The supplementation with alpha-tocopherol (400 IU/d) and beta-carotene (30 mg/d) or placebos was administered during radiation therapy and for 3 years thereafter. During the course of the trial, supplementation with beta-carotene was discontinued because of ethical concerns.

RESULTS

Patients randomly assigned in the supplement arm tended to have less severe acute adverse effects during radiation therapy (odds ratio [OR], 0.72; 95% CI, 0.52 to 1.02). The reduction was statistically significant when the supplementation combined alpha-tocopherol and beta-carotene for adverse effects to the larynx (OR, 0.38; 95% CI, 0.21 to 0.71) and overall at any site (OR, 0.38; 95% CI, 0.20 to 0.74). Quality of life was not improved by the supplementation. The rate of local recurrence of the head and neck tumor tended to be higher in the supplement arm of the trial (hazard ratio, 1.37; 95% CI, 0.93 to 2.02).

CONCLUSION

Supplementation with high doses of alpha-tocopherol and beta-carotene during radiation therapy could reduce the severity of treatment adverse effects. However, this trial suggests that use of high doses of antioxidants as adjuvant therapy might compromise radiation treatment efficacy.

A Randomized Trial of Antioxidant Vitamins to Prevent Second Primary Cancers in Head and Neck Cancer Patients

BACKGROUND

Although low dietary intakes of antioxidant vitamins and minerals have been associated with higher risks of cancer, results of trials testing antioxidant supplementation for cancer chemoprevention have been equivocal. We assessed whether supplementation with antioxidant vitamins could reduce the incidence of second primary cancers among patients with head and neck cancer.

METHODS

We conducted a multicenter, double-blind, placebo-controlled, randomized chemoprevention trial among 540 patients with stage I or II head and neck cancer treated by radiation therapy between October 1, 1994, and June 6, 2000. Supplementation with alpha-tocopherol (400 IU/day) and beta-carotene (30 mg/day) or placebo began on the first day of radiation therapy and continued for 3 years after the end of radiation therapy. In the course of the trial, beta-carotene supplementation was discontinued after 156 patients had enrolled because of ethical concerns. The remaining patients received alpha-tocopherol or placebo only. Survival was evaluated by Kaplan-Meier analysis. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). All statistical tests were two-sided.

RESULTS

After a median follow-up of 52 months, second primary cancers and recurrences of the first tumor were diagnosed in 113 and 119 participants, respectively. The effect of supplementation on the incidence of second primary cancers varied over time. Compared with patients receiving placebo, patients receiving alpha-tocopherol supplements had a higher rate of second primary cancers during the supplementation period (HR = 2.88, 95% CI = 1.56 to 5.31) but a lower rate after supplementation was discontinued (HR = 0.41, 95% CI = 0.16 to 1.03). Similarly, the rate of having a recurrence or second primary cancer was higher during (HR = 1.86, 95% CI = 1.27 to 2.72) but lower after (HR = 0.71, 95% CI = 0.33 to 1.53) supplementation with alpha-tocopherol. The proportion of participants free of second primary cancer overall after 8 years of follow-up was similar in both arms.

CONCLUSIONS

alpha-Tocopherol supplementation produced unexpected adverse effects on the occurrence of second primary cancers and on cancer-free survival.