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Thyroid Cancer Diagnosis and Treatment / Thyroid Disorders and Treatments / Advanced Breast Cancer Therapies · Journal article
BMC Cancer · August 14, 2026
Encouraging direction, but not yet definitive.
This retrospective cohort study of 162 HR+/HER2− metastatic breast cancer patients treated with CDK4/6 inhibitors reports that a high fT3/fT4 ratio is associated with longer progression-free and overall survival. The findings are statistically significant but derive from a single centre without external validation or mechanistic support.
Retrospective cohort study. HR+/HER2− metastatic breast cancer patients treated with CDK4/6 inhibitors; 162 enrolled; no exclusion criteria stated.. Intervention: High fT3/fT4 ratio (≥median value).. Compared with: Low fT3/fT4 ratio (<median value).. n = 162. Hacettepe University Hospital (single centre, Turkey implied by institution name)..
High fT3/fT4 ratio associated with median PFS of 9.7 months vs. 6.9 months in Low group (HR 0.68; 95% CI 0.47–0.97; p = 0.035) High fT3/fT4 ratio associated with significantly longer overall survival vs. Low group (HR 0.30; 95% CI 0.15–0.60; p < 0.001) No significant differences in baseline characteristics (age, grade, menopausal status, metastasis sites, prior treatment lines) between ratio groups
Safety was not reported in the material analysed. Check the source before drawing any conclusion about harm.
If confirmed in prospective studies, fT3/fT4 ratio could serve as a simple, inexpensive prognostic biomarker to stratify risk in CDK4/6 inhibitor–treated metastatic breast cancer. Clinicians should view this as hypothesis-generating rather than practice-changing until external validation and mechanistic understanding are established.
Single-centre retrospective cohort study with clinical endpoints (PFS, OS) in a defined population, showing statistically significant associations, but limited by retrospective design, lack of mechanistic validation, and absence of external validation.
As stated by the source record.
Quoted from the source exactly as published.
If confirmed in prospective studies, fT3/fT4 ratio could serve as a simple, inexpensive prognostic biomarker to stratify risk in CDK4/6 inhibitor–treated metastatic breast cancer. Clinicians should view this as hypothesis-generating rather than practice-changing until external validation and mechanistic understanding are established.
Graded across the dimensions that decide whether you should act, each from what the source actually supports. There is no single score, and where a dimension was not assessed it says so.
The free triiodothyronine (fT3)/free thyroxine (fT4) ratio is an index estimating the peripheral activity of thyroid hormones. The prognostic role of the fT3/fT4 ratio in colorectal cancer, urothelial cancer, renal carcinoma, and lymphoma is well-recognized, but its effect in metastatic breast cancer remains unestablished. We conducted a retrospective study of metastatic breast cancer patients treated with cyclin-dependent kinase (CDK) 4/6 inhibitors at Hacettepe University Hospital. Baseline fT3 and fT4 levels were recorded, and patients were categorized into two groups based on the median fT3/fT4 ratio: Low and High fT3/fT4 Ratio Groups. We included 162 h-positive/HER2-negative metastatic breast cancer patients. There were no significant differences between the Low and High fT3/fT4 Ratio Groups in terms of age, sex, tumor grade, histopathologic type, menopausal status, sites of metastases, lines of treatment prior to CDK4/6 inhibitors, type of CDK4/6 inhibitor, or endocrine backbone therapy. Of all patients, 47 (29.2%) received two or more lines of treatment before initiating CDK4/6 inhibitors. High fT3/fT4 ratios were associated with significantly longer progression-free survival (PFS) compared to Low fT3/fT4 ratios (median, 9.7 vs. 6.9 months; HR: 0.68; 95% CI: 0.47–0.97; p = 0.035) and significantly longer overall survival (OS) compared to Low fT3/fT4 ratios (median, NR vs. NR months; HR: 0.30; 95% CI: 0.15–0.60; p < 0.001). Our study showed that high fT3/fT4 ratios were independent factors associated with longer PFS and OS in metastatic breast cancer patients treated with CDK4/6 inhibitors, supporting the role of high fT3/fT4 ratios as a prognostic marker.
Taken from the source record, never inferred. Follow any of these and new work involving them reaches your briefing.