Obesity could increase the risk of breast cancer in women whose risk is already higher because they carry the BRCA1 and BRCA2 genetic mutations, warns a study in which a Montreal researcher participated.
In particular, researchers have found a direct correlation between a woman’s body mass index and genetic damage to the milk glands. This damage is thought to be due to the effect of three hormones: leptin, insulin, and estrogen.
Weight management and medication could therefore play a role in reducing the risk in these women.
“Everyone wants to prevent cancer, but these people have to work harder because their risk is higher,” said Dr. Michael Pollak, of McGill University’s Faculty of Medicine. The usual treatment involves removal of the breasts and ovaries, and it’s effective, but it’s a bit traumatic.
“This study suggests that, in those people who have the mutation and are also obese, correcting metabolic problems may reduce risk. »
The study authors found that obese mice that had been genetically engineered to express the BRCA1 mutation developed cancerous tumors earlier and more frequently than normal-weight mice.
The researchers also found in lab experiments that they could reduce genetic damage in tissue samples by exposing them to metformin, a drug commonly used in the control of type 2 diabetes.
“Weight loss and metformin can help reduce the risk (of breast cancer in obese women), Dr. Pollak summarized. It’s not proven in humans, but there’s no downside to reaching an ideal body weight. »
Especially, he continues, since metformin is a drug known and used for a long time, which has few side effects. For people who are both obese and carriers of these genetic mutations, “this is an approach that deserves further investigation,” Dr. Pollak said.
Metformin has also been attracting the attention of researchers to fight breast cancer for several years. A large clinical study whose results were recently published concluded that the drug did not work, but the study only wanted to know if taking metformin would improve the outcome of average breast cancer patients.
It is therefore important not to “over-generalize” the results of this study, stressed Dr. Pollak.
“Our mouse study suggests that, in some people, carriers (of the mutations) who are also obese may benefit,” he said.
Another study, this one published in January in the prestigious journal Science by British researchers, shows that the family of drugs to which metformin belongs deserves further study in the context of the fight against cancer, added the Dr Pollack.
The subject is therefore far from closed, and it would therefore not be superfluous for an obese woman to discuss metformin with her doctor, he believes.
It is estimated that between a quarter and a third of cancer cases could be avoided, recalls Dr. Pollak, and even patients who are ultimately cured would certainly have preferred never to go through this ordeal.
“Prevention is clearly superior to treatment,” he said. An opportunity to prevent cancer should never be missed. It is not necessary to find a way to prevent all cancers to justify the efforts. »
People with obesity know they should lose weight, for example to protect their cardiovascular health, the researcher continued. The possibility of reducing their risk of cancer could provide some with the extra motivation they need to walk the talk.
But this is only a “possibility”, he insists: some people who lead an exemplary lifestyle will still suffer from cancer, while others who smoke two packs of cigarettes a day will never be troubled by the disease.
There are no guarantees, he added. Even a careful driver who puts the odds in his favor and takes every precaution can have a traffic accident.
“Just because it’s not guaranteed doesn’t mean it’s not important,” he said. You can only promise to reduce the risk, not eliminate it. But if you can live with high risk or with low risk, why not choose low risk? »
The findings of this study were recently published by the journal Science Translational Medicine.