Stomach and gallbladder cancer: the Chilean phenomenon

Based on world statistics, the Chilean population presents notoriously higher than average mortality and incidence rates for both stomach and gallbladder cancers. Stomach cancer has historically been one of the principal causes of cancer related death worldwide. However, while rates have declined in westernized populations of North America, Northern and Western Europe, regions such as South America still post high mortality rates.

While stomach cancer is currently the most common malignancy in Chile, in the United Kingdom (UK), stomach cancer no longer figures as one of the ten most common cancers, with the incidence rate having fallen by over 60% since the mid-70s. In 2009, Chile registered 3,350 deaths from stomach cancer giving a rate of 19.8 per 100,000 inhabitants.

As has been reported globally there is also a strong correlation between stomach cancer and the indigenous population. This is also true in Chile, where between 1998 and 2002, a crude incidence rate of 29.2 per 100,000 inhabitants was reported in the city of Valdivia in the mid-southern region of the country. Most stomach cancer patients are male, with urban residence and a low level of schooling. Along with social determinants and advanced clinical stage at consultation, infection with the bacteria Helicobacter pylori is also recognized as a principal risk factor for stomach cancer in the Chilean population. In addition, Helicobacter infection has been associated to lower socioeconomic structure. This observation is in line with statistics implicating the involvement of infection in 22.9% of cancers in lower income countries, as opposed to 16% globally.

Another factor in the Chilean stomach cancer story is salt. In Chile, it is estimated that the average salt (NaCl) consumption is around 10.4 g per day in adults. This value is significantly higher than in British adults who consume on average 8.1 g per day. The interaction between salt, Helicobacter and genetic predisposition in the Chilean population are likely to underlie this high incidence. However, genetic factors aside, these above mentioned risk factors suggest that prevention, through health education and eradication of Helicobacter pylori, together with better screening procedures for precancerous lesions may well deliver a notable improvement in incidence and prognosis to the Chilean population.

While stomach pattern follows a worldwide trend in reducing as socioeconomic status increases, a statistic that is uniquely Chilean is the incidence of gallbladder cancer. In the UK, gallbladder is considered a rare cancer, with 700 new cases and 438 deaths recorded in 2008. Chile recorded 1819 deaths from gallbladder and bile duct related cancer in the same year. Further emphasizing the gallbladder problem, in Chile the estimated incidence and mortality rates for this cancer are 13.4 and 11.5 per 100,000 female habitants, while in Latin-American these rate are 3.7 and 3.0, and in the USA 1.6 and 0.6 respectively. The highest risk group for gallbladder cancer is among Amerindians, Mapuche and Hispanic women with less than four years of schooling. On the other hand, the lowest standardized incidence rates were among Hispanic men and women with more than eight years of schooling. Thus, ethnic origin, low schooling, the female sex and urban residence were deemed independent risk factors. In the Mapuche population, the incidence of gallbladder cancer has reached 269.2 per 100,000 women in specific age groups. Interestingly, cholelithiasis is always a precursor to gallbladder cancer, suggesting that screening programs and cholecistectomy could significantly decrease gallbladder cancer death. A pilot study of gallbladder cancer lead by the US-National Institute of Health (NIH) (Government trial identifier NCT01520259) in conjunction with Chilean Universities intends to recruit 120 cases to assess the feasibility of a full-scale population based multidisciplinary gallbladder cancer study. Another recognized risk factor is the chronic carriage of Salmonella typhi, which would be the long-term effect of the hyperendemic of Typhoid Fever that occurred in Chile during the 1970s and 80s. As Chile moves towards a more westernized lifestyle, the risk factors and incidence are likely to fall, however, the sheer numbers of gallbladder cancer cases in Chile suggests a genetic or environmental factor that is not being fully addressed by the nation’s scientific and medical community.

Another malignancy that demonstrates peculiar statistics in Chile is lung cancer. The majority of Chile presents slower than developed country incidence rates. However, the occurrence of high arsenic exposure in drinking water (>200 ug/L as opposed to now recommended <10 ug/L) from 1930 to 1977 in the Antofagasta Region in the north of the country and in particular levels of 860 ug/L in the City of Antofagasta between 1958 to 1970 has resulted in high lung cancer incidence and mortality. Despite water filters and regulations being introduced in the 1970s, a significantly high odds ratio to develop lung and bladder cancer in this region still exists up until today. However, not all cancers increased in mortality. A recent publication has speculated a rapid reduction in breast cancer mortality in the years during and directly following exposure to arsenic-contaminated drinking water in Antofagasta.

I, having cancer living in similar place based on salt that might be consumed at higher levels than most area of the rest of the world.

We as the human race need to see how we can change our environment for it is a nature vs. nurture life.

– jmm