Re: “High Altitude and Cancer Mortality” by Thiersch and Swenson (High Alt Med Biol 2018;19:116–123)

To the Editor

We wish to comment on the recently published review entitled High Altitude and Cancer Mortality (Thiersch and Swenson, 2018).

The adaptation of humans to the high-altitude environment is a complex phenomenon that may differ among ethnic groups as was proposed between Tibetans and Andeans. Even if both the populations are exposed to the hypoxic and hypobaric conditions as observed in the high-altitude regions, differences varying from dietary habits to single-nucleotide polymorphism exist. These single-nucleotide polymorphisms were associated with a “maladaptation” to live at high altitude by the Andean population (Villafuerte, 2015). In this context, recent publications have suggested that people living in the Andean region, especially of South America, are at higher risk of suffering or dying from cancer. A study that includes data of cancer from Latin America showed an association of gastric cancer incidence with mortality and altitude, in the countries of western Latin America that falls along the Pacific Rim (Torres et al., 2013). However, this could be a multifactorial phenomenon that deserves a detailed investigation to understand the underlying mechanism. Similarly, a recent article concludes that gallbladder cancer has a high incidence in the Andean region of South America, and is a frequent cause of death from cancer, particularly in women (Gallardo et al., 2018). In addition, living in Ecuadorian Andean region is also associated with an increased risk of developing or dying from diverse types of cancer including gastric, colorectal, breast, liver, and intrahepatic bile duct (Garrido and Garrido, 2018).

Numerous articles published in this area indicate the risk association of cancer in people living in the Andean high altitude. However, there is no conclusive evidence of high altitude per se as being the main reason for thereby explaining the results obtained. Therefore, it is necessary to investigate every aspect that could be modified or controlled by national authorities in health. Also, it would be helpful in continuing the search for a detailed characterization of the adaptation to the high altitude in Andean people and its impact in cancer biology.