Objective:

To assess whether blood concentrations of PFAS are associated with breast cancer risk, including ER-negative disease.

Approach:

• Study population: Researchers analyzed data from the Sister Study, including 1,609 women who developed breast cancer and 2,269 comparison participants. Blood samples were collected years before diagnosis.
• Exposure assessment: The investigators assessed 17 PFAS and examined associations with breast cancer overall and by estrogen receptor status. They also conducted a meta-analysis of earlier research.

Key Findings:

• Higher blood concentrations of PFOA and PFOS were associated with increased incidence of ER-negative breast cancer.
• Compared with the lowest exposure groups, the highest PFOA group had a 67% higher rate of ER-negative breast cancer; the highest PFOS group had a 93% higher rate.
• Neither chemical showed a clear association with overall breast cancer risk.
• The reported percentages are relative differences between groups, not individual probabilities of developing breast cancer.

Interpretation:

The authors proposed that PFAS could affect risk through non-hormonal pathways, such as altered gene activity or immune-system effects, but the study did not investigate these mechanisms.

Limitations:

• The observational findings show associations and do not establish that PFOA or PFOS caused breast cancer.
• The proposed biological mechanisms were not examined.
• The study population consisted of women with a sister previously diagnosed with breast cancer.
• The analysis focused on selected legacy PFAS; the authors called for further research on newer replacement PFAS.

Conclusion:

The authors stated that further research is needed, including studies of people with higher PFAS exposure and populations more affected by ER-negative breast cancer.

Sources:

• Article context; Journal of Clinical Oncology study described