Dioxin and PCBs are persistent pollutants that could promote the development of breast cancer metastases, according to preliminary research by Inserm researchers published in the November edition of the journal Environment International . Breast cancer is a major public health issue with more than 2 million new cases diagnosed and more than 600,000 deaths worldwide in 2018, the authors note.
Associated with the size of the tumor
The presence of distant metastases from the tumor of origin is a marker of aggressiveness of this cancer, Inserm emphasizes. When metastases are detected, the five-year survival rate of the diagnosis is only 26%, compared to 99% if the cancer affects only the breast, and 85% if only the lymph nodes are also affected. Recent studies have suggested that exposure to persistent organic pollutants or POPs (endocrine disrupting and / or carcinogenic environmental pollutants that the body can not eliminate), which accumulate in the food chain, would be a risk factor for cancer. breast.
To evaluate the influence of these POPs on the level of cancer aggressiveness, which has been poorly studied, researchers have measured the concentration of 49 POPs, including Seveso dioxin (a waste from incineration products) and several PCBs ( generated by various industrial processes) in fat samples surrounding breast cancer of 91 women. The biological and statistical analysis shows an association between the presence of metastases at a distance from the tumor and the dioxin concentration in the adipose tissue of overweight women. In all patients, dioxin and PCB concentrations (for two of those measured) were associated with tumor size and invasion and metastatic lymph node levels.
Increased risk of re-offending
Women with higher PCB concentrations had a higher risk of recurrence. These results suggest that the higher the concentration of POPs in adipose tissue, the more aggressive breast cancer is, especially in overweight women.
According to one of the hypotheses likely to explain these results, the dioxin and certain PCBs would send a signal that would promote the migration of the cancerous cells, thus the metastases. The study, "preliminary", "does not allow to draw firm conclusions" on the link between POPs and aggressiveness of breast cancer. But research on more patients should provide more representative statistical results.