# PFOA and PFOS linked to ER-negative breast cancer in Sister Study cohort

- Published: 2026-11-14 07:17 UTC
- Section: Life & Health › Medicine
- Tags: PFAS and breast cancer, PFOA, PFOS, ER-negative breast cancer, Sister Study, case-cohort study, prediagnostic plasma, Journal of Clinical Oncology, meta-analysis
- URL: https://realtech.media/news/rt-4162daea4ad87c50b949e393_pfoa_and_pfos/

**In a case-cohort analysis of 1,609 cases, higher plasma PFOA and PFOS were associated with ER-negative breast cancer, a type with few established risk factors.**

![PFOA and PFOS linked to ER-negative breast cancer in Sister Study cohort](https://realtech.media/media/2026/11/77486c9ab7c36d1b.webp)
*cancertherapyadvisor.com*

A case-cohort study within the Sister Study, published online on November 5, 2026 in the Journal of Clinical Oncology, examined 17 per- and polyfluoroalkyl substances (PFAS) in plasma collected before diagnosis. It included 1,609 breast cancer cases and 2,269 subcohort participants [1]. The authors, led by Chang C-J, report that PFOA and PFOS were associated with estrogen receptor (ER)-negative tumors [1].

The Sister Study enrolled more than 50,000 women aged 35 to 74 years who have a full or half-sister with a breast cancer diagnosis.

## Design and methods

To improve statistical power, the researchers oversampled ER-negative cases: the analysis included 324 ER-negative and 1,120 ER-positive tumors [1]. PFAS were quantified using liquid chromatography-high-resolution mass spectrometry. Sampling-weighted Cox models estimated associations with overall breast cancer incidence and by hormone receptor status, adjusting for confounders and coexposures [1].

Median baseline age was 57.2 years in the case population and 55.6 years in the subcohort, with median follow-up of 5.9 and 9.7 years, respectively. PFAS concentrations were similar in cases and the subcohort and comparable to levels in the US population survey NHANES.

## Associations by receptor status

Comparing the highest and lowest exposure quartiles, ER-negative tumors were positively associated with PFOA (hazard ratio 1,67; 95% CI 1,10 to 2,53) and PFOS (hazard ratio 1,93; 95% CI 1,15 to 3,22) [1]. N-MeFOSAA showed a possible association (hazard ratio 1,42; 95% CI 0,99 to 2,04). PFTrDA was inversely associated with ER-negative tumors (hazard ratio 0,63; 95% CI 0,41 to 0,97) [1].

PFOSA, detected in 6.9% of samples, was positively associated with ER-positive tumors when detectable versus nondetectable (hazard ratio 1,36; 95% CI 1,03 to 1,81) [1]. No associations were found between PFOA or PFOS and ER-positive tumors.

The meta-analysis of seven studies with prediagnostic blood PFAS measurements gave a relative risk of 1,30 (95% CI 1,05 to 1,62) for PFOA and 1,20 (95% CI 0,91 to 1,58) for PFOS with ER-negative breast cancer [1]. The authors concluded that PFOA and PFOS may increase ER-negative breast cancer risk, and recommended that future studies support targeted prevention and characterize newer PFAS replacement chemicals.

## Sources

1. [Journal of Clinical Oncology](https://doi.org/10.1200/JCO-26-00318)
2. [cancertherapyadvisor.com](https://www.cancertherapyadvisor.com/news/plasma-pfas-levels-er-negative-breast-cancer-risk)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-4162daea4ad87c50b949e393_pfoa_and_pfos/