KEY POINTS
- This retrospective cohort included 126 patients with gynecologic malignancies receiving extended-field or salvage para-aortic RT between 2000 and 2023. Patients with baseline eGFR <60 mL/min/1.73 m² were excluded, and prescribed para-aortic doses ranged from 39.6–62 Gy in 22–31 fractions.
- Median mean kidney dose was 5.65 Gy. Patients were grouped as <5 Gy (n=52), 5–9.9 Gy (n=49) and ≥10 Gy (n=25), with death without CKD treated as a competing event rather than conventional censoring.
- Seven-year stage ≥3A CKD incidence rose from 17.0% to 20.9% to 55.7% across the three dose groups (p=0.008). For the more clinically significant stage ≥3B endpoint, incidence was 0%, 13.9% and 26.4%, respectively (p=0.041).
- Renal function declined across the entire cohort: mean eGFR fell from 93.2 to 76.9 mL/min/1.73 m² (p<0.001). The largest decline occurred in patients receiving ≥10 Gy mean kidney dose, from 88.7 to 64.2 mL/min/1.73 m².
- Baseline renal reserve strongly modified risk. With pre-RT eGFR <75 mL/min/1.73 m², seven-year stage 3B CKD incidence was 37.2% versus 7.6% for patients with higher baseline eGFR (p=0.005); stage 3A incidence was 57.1% versus 23.2%.
- In Fine–Gray competing-risk analysis, both kidney dose group (sHR 3.30, 95% CI 1.30–8.35; p=0.012) and baseline eGFR <75 (sHR 4.29, 95% CI 1.22–15.08; p=0.023) independently predicted stage 3B CKD.
- Only nine stage 3B events occurred, and treatment spanned more than two decades using 3DCRT, IMRT, VMAT and proton therapy. The proposed <5-Gy goal therefore requires prospective validation before replacing established kidney constraints.
CLINICAL TAKEAWAY
For para-aortic RT in gynecologic cancer, kidney dose may matter well below the traditional QUANTEC mean-dose ceiling of 15–18 Gy. When achievable, keeping mean kidney dose <5 Gy may be particularly attractive in patients starting with eGFR <75, but this remains retrospective evidence rather than a validated new constraint.