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Chronic Helicobacter pylori infection is associated with gastric cancer, but could its eradication in chronic carriers prevent gastric cancer? Wong et al. performed the first prospective, randomized, placebo-controlled, population-based study to determine whether H. pylori eradication in a high-risk population reduced the incidence of gastric cancer.

The study was performed in a high-risk region of southern China and involved 1,630 carriers of H. pylori infection — 988 of whom did not have any precancerous lesions, as determined by endocscopic evaluation. H. pylori was eradicated in the participants through combination treatment with omeprazole and antibiotics. After a follow-up of 7.5 years, the authors report that the incidence of gastric cancer was similar among participants who received H. pylori eradication treatment and those who received placebo (7 and 11 cases, respectively). In those carriers who did not have precancerous lesions, however, eradication of H. pylori seemed to prevent the development of gastric cancer — none of the treated patients developed gastric cancer, whereas 6 in the placebo group did.

Although H. pylori eradication seems to be effective in preventing gastric cancer in high-risk populations, further studies are required to determine the effects in low-risk populations, and also to determine the long-term effects of antibiotic treatment in patients with precancerous lesions. ORIGINAL RESEARCH PAPER Chun-Yu Wong, B. et al. Helicobacter pylori eradication to prevent gastric cancer in a high-risk region of China — a randomized controlled trial. JAMA 291, 187–194 (2004)

Insufficient evidence

It is a common belief that participating in clinical trials leads to a better outcome for patients with cancer, regardless of whether they are assigned to the control or experimental group of the study. But, researchers at the Dana–Farber Cancer Institute have found little evidence to support this 'trial effect' and advocate that it should no longer be emphasized as an incentive for patient recruitment.

Peppercorn et al. systematically looked for studies that presented primary data comparing the outcome of patients with cancer, within and outside clinical trials. The identified studies were critically evaluated for evidence of a trial effect using a conceptual framework designed by the authors. Only 14 of the 26 identified studies showed evidence of improved outcomes for trial participants, but most were unreliable, as they did not effectively control for study bias such as co-morbidity, socio-economic status and performance status. Eight studies compared trial participants with non-trial participants who met the criteria for trial selection, but only 3 showed improved outcome for trial participants. In addition, the studies showing improved outcome tended to involve children with cancer, patients treated before 1986 and patients with haematological malignancies.

This work indicates that there is insufficient evidence to confirm that the trial effect exists. Even though there might be no immediate benefit from participating in a clinical trial, it is important for trial participants to realize the benefit for future patients. ORIGINAL RESEARCH PAPER Peppercorn, J. M., Weeks, J. C., Cook, E. F. & Joffe, S. Comparison of outcomes in cancer patients treated within and outside clinical trials: conceptual framework and structured review. Lancet 363, 263–270 (2004)