Gastric cancer: Which lifestyle, nutritional factors should we look closely out for?

A secondary analysis of a randomized clinical trial revealed lifestyle and nutritional factors that could factor in the development of gastric cancer (GC).

“Given our ongoing efforts to promote precision prevention and control of GC, it [is] important to illuminate the effects of intervention strategies on subgroups based on lifestyle factors and to identify any effect modifications by lifestyle factors on GC prevention resulting from long-term nutritional supplementation,” said the researchers.

Smoking was associated with an increased risk of GC incidence (odds ratio [OR], 1.72) and mortality (hazard ratio [HR], 2.01), which were magnified among those with Helicobacter (H.) pylori (OR, 1.88 and HR, 2.15, respectively). [JAMA Netw Open 2020;3:e206628]

“The increased exposure to potent carcinogens and N-nitroso compounds when smoking may partly help to explain the increased risk of GC among [smokers],” said the researchers. “H. pylori infection [may play] a crucial role in the initial steps of [gastric] carcinogenesis by causing enhanced inflammation and histological changes,” they added.

What can be protective against GC?

Garlic supplementation appeared protective against GC mortality, owing to the allyl sulphur compounds in garlic known to be effective against carcinogenesis. [J Nutr 2001;131:1027S-1031S] However, the significant effect was only observed among those who never drank alcohol (HR, 0.33 vs 0.92 [ever drinkers]; p_interaction=0.03), suggesting that alcohol may alter the protective effect of garlic supplementation against GC, underscored the researchers.

Vitamin supplementation seemed protective against gastric lesion progression among those who had a total consumption of fresh fruit/vegetable intake of <81 kg/year (OR, 0.80 vs 1.17 [≥81 kg/year]; p_interaction=0.02). “[However,] the significant interaction was only seen for gastric lesion progression but not for GC incidence or mortality. The reason for this is unclear,” said the researchers.

“[Nonetheless,] during gastric carcinogenesis, the pH level in the stomach decreases initially but increases with gastric lesion progression when vitamin C (ie, ascorbic acid) is converted to the less active form of dehydroascorbic acid, [which might offer] weaker protection,” they continued. [Eur J Gastroenterol Hepatol 2001;13:233-237]

Tailored strategies

This analysis was based on the Shandong Intervention Trial (n=3,365*; mean age 47 years, 49 percent female). Half of the cohort received active garlic supplementation** while the other half received active vitamin supplementation*** for 7.3 years (50 percent of each arm received placebo). Participants with H. pylori received H. pylori treatment for 2 weeks or placebo. Follow up was 22.3 years.

A total of 151 GC cases and 94 GC deaths were identified. Gastro-endoscopy and histologic examination results revealed a 43-percent incidence of gastric lesion progression.

Despite the modest sample size, lack of detailed data^# on lifestyle factors and/or changes, and the rural sample that might preclude extrapolation of results to the general population level, the well-defined high-risk population and long-term follow up may have strengthened the findings, explained the researchers.

“Our findings provide new insights into lifestyle interventions for GC prevention, suggesting that mass GC prevention strategies may need to be tailored to population subgroups to maximize the potential beneficial effects,” they said.