First thesis based on the Karma Study published

On the 15th of January, Dr Thang Thrinh, Karolinska Institutet, defended his thesis entitled ”Determinants of breast cancer risk; focusing on mammographic density”. Thang’s thesis deals with how physical activity, alcohol consumption and cigarette smoking affect the risk of breast cancer through their influence on mammographic density.

Mammographic density is defined as the radiographically dense tissue, consisting of glandular and connective tissues, appearing bright on a mammogram, whilst non-dense, fatty tissue appears dark on a mammogram. The more bright the mammogram, the more glandular cells and the higher the risk of developing breast cancer. See images below (left: non-dense breast, right: highly dense breast).

Women who participated in the Karma study answered a large number of questions related to lifestyle when they entered the study. Participants were invited to the study when they performed the biannual mammography screening. Dr Thang wanted to find out if women who, for example, drank more wine had more dense breasts than women who totally abstained from alcohol.

In short, the conclusions that could be drawn from this thesis was:

Women who were physically active had a lower mammographic density, which most certainly reduces the risk of breast cancer. The more vigorous the physical activity, the lower the breast density. We also wanted to find out if women with an increased risk of breast cancer needed to do harder physical exercise than women with a lower risk. Background risk of breast cancer was estimated using the Tyrer – Cuzick score. Our findings suggested that women with a higher background risk of breast cancer needs to be more physically active, to reduce breast density, than women with lesser background risk.

Regarding alcohol consumption the findings are quite the opposite. The more alcohol a woman drinks, the higher the breast density and the higher the risk of breast cancer. However, it seems that daily consumption of wine has to exceed 1 glass wine/day to influence breast density. Similar to the findings of physical activity, background risk of breast cancer influenced how alcohol affects mammographic density. If you have a high risk of breast cancer you should be careful with alcohol.

Finally dr Thang studied change in mammographic breast density among cigarette smoking women. Surprisingly enough, in women who smoke the density is lower than in non-smoking women, despite the fact that smoking is known to increase the risk of breast cancer. Thang explained the effect of cigarette smoking on breast density as tobacco having an ”anti-hormonal” effect (which lowers the density) but that tobacco contains so many other toxic / carcinogenic substances that increase the risk of breast cancer so the overall effect is an increased risk of breast cancer.

Professor Per Hall, dr Thang’s supervisor, comments on the results: ”The findings are exciting and show that in the future, when we are able to predict a woman’s individual risk of breast cancer, lifestyle related advise can be given in preventive breast cancer care. As a matter of fact, already today, we can advise women who wish to reduce their risk of breast cancer to be physically active, drink moderately and not to smoke.

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