Marina Pollán
Cancer epidemiologist and Director General of the Carlos III Health Institute
Is the study based on solid data and methods?
"Yes. Obviously, this estimate is based on a pragmatic approach to obtain global results from all available information. The number of cancer cases worldwide is itself an estimate, as many countries, including ours, do not have cancer registries with national coverage, and in some countries there are no registries at all. Furthermore, as the authors themselves acknowledge, the latency period used (10 years) may not be the most appropriate for all locations and/or all age groups. There are therefore many sources of uncertainty, but the study provides solid information on many of the fully established modifiable cancer risk factors to give an estimate of the percentage of cases that could be prevented if these factors were eliminated.
What new information does it provide?
‘The study expands the list of risk factors considered, uses cancer incidence (not mortality) data and provides, I believe for the first time, estimates for 185 countries in addition to large geographical regions, as well as a comparison of the main preventable factors by tumour type. This effort was led by the IARC. In addition to being up-to-date data, I believe that having this information is very relevant.’
Are there any important limitations to consider?
"The authors discuss the main limitations in the article, some of which have already been mentioned. Perhaps the most important is the impossibility of taking into account the combined effect of different risk factors with synergistic effects, i.e., with a greater effect than expected considering the role of each of these exposures or risk factors. This implies that these estimates are possibly conservative and that the benefit of avoiding these determinants or risk factors would be even greater."
How relevant is this study to clinical practice in Spain?
"The main conclusion of this study is the value of prevention in effectively reducing the burden of cancer on our population. Furthermore, quantifying the effect of each of the factors considered also serves to prioritise efforts in this direction. Clearly, in our context (Figure 3), tobacco, alcohol, infectious agents, obesity and a sedentary lifestyle are the main factors to avoid. It is interesting to note the differences between men and women; in the former, the weight of tobacco is much greater. It is also important to consider factors such as pollution or occupational exposures that cannot be modified individually and must be taken into account in the protective measures proposed by the public authorities."