Dosimetric correlation of radiation-induced chronic kidney disease (CKD): a competing risks analysis.

BACKGROUND AND PURPOSE: To determine the competing risks (CR) cumulative incidence of radiation-induced chronic kidney disease (CKD) and identify independent dosimetric predictors in patients receiving radiotherapy (RT) involving the para-aortic lymph nodes (PALNs), providing evidence to refine kidney dose constraints in contemporary RT planning.

MATERIALS AND

METHODS

From November 2000 to September 2023, 126 patients with gynecological malignancies receiving extended-field RT (EFRT) or salvage PALN RT were retrospectively analyzed. The planned PALN dose was 39.6-62 Gy/22-31 fractions. Patients with baseline estimated glomerular filtration rate (eGFR) < 60 ml/min/1.73 m2 were excluded. CKD was defined as stage 3A (eGFR < 60 ml/min/1.73 m2) or stage 3B (eGFR < 45 ml/min/1.73 m2). Mean kidney dose (MKD) groups: Group 1 (<5 Gy), Group 2 (5-9.9 Gy), and Group 3 (≥10 Gy). CR analysis with Gray's test and the Fine-Gray subdistribution hazard model accounted for the competing risk of death without CKD.

RESULTS

After a median follow-up of 55 months, 7-year CR cumulative incidences of stage ≥ 3A CKD were 17.0 %, 20.9 %, and 55.7 % in Groups 1, 2, and 3 (p = 0.008), respectively; corresponding rates for stage ≥ 3B CKD were 0 %, 13.9 %, and 26.4 % (p = 0.041). Patients with pre-RT eGFR < 75 ml/min/1.73 m2 had significantly higher 7-year CR rates of stage 3A (57.1 % vs. 23.2 %; p < 0.001) and stage 3B CKD (37.2 % vs. 7.6 %; p = 0.005). Multivariate CR analysis identified MKD group (p = 0.012) and pre-RT eGFR < 75 ml/min/1.73 m2 (p = 0.023) as independent predictors of stage 3B CKD.

CONCLUSIONS

Radiation-induced CKD is significantly correlated with MKD and baseline eGFR. Even MKD values of 5-9.9 Gy carry measurable risk of stage 3B CKD-below the QUANTEC-recommended ceiling of 15-18 Gy-suggesting that stricter MKD constraints (< 5 Gy) are warranted, particularly in patients with pre-RT eGFR < 75 ml/min/1.73 m2.