Renal cancer prognostication improved with latest TNM staging system
MedWire News: The latest version of the TNM Classification of Malignant Tumors for renal cell carcinoma (RCC) more accurately predicts the outcome of patients with T3a tumors, compared with the previous version, UK researchers report.
The previous 2002 TNM classification for RCC described T1 (<7 cm), T2 (>7 cm), T3a (perinephric fat, renal sinus fat, or adrenal gland invasion), T3b (renal vein or subdiaphragmatic inferior vena cava invasion), T3c (supradiaphragmatic inferior vena cava invasion), and T4 tumors (invasion outside Gerota's fascia).
In the new classification - which came into effect in January 2010 (7th edition) - T2 cancers are now classified into two subgroups based on tumor size (T2a ≤10 cm and T2b >10 cm), contiguous adrenal invasion is reclassified from T3a to T4, and invasion of the renal vein by tumor from T3b to T3a, which also includes renal fat invasion (peripheral and sinus).
Rakesh Heer (Newcastle University) and colleagues explain that the changes were based on growing evidence that reassignment of pathological features to specific stages would more accurately predict the cancer-specific survival associated with increasing TNM stage.
To assess whether this was indeed the case, the researchers compared the accuracy of predicting outcomes using the 2002 and 2010 TNM staging systems in a cohort of 345 patients with RCC treated at a tertiary referral centre in the north-east of England.
Based on the 2002 TNM staging system, 199 patients had localized disease (pT1/T2), 100 patients had locally advanced disease (pT3/4), and 46 patients had nodal or metastatic disease.
Reclassification of the tumors according to the 2010 TNM staging system resulted in 52 tumors with renal vein invasion (T3b according to 2002 TNM) being reassigned to T3a. In addition, three tumors that exhibited adrenal invasion (previously T3a) were upstaged to T4.
Despite the revision of the TNM classification, the absolute number of patients in the three groups (localized disease pT1/T2, locally advanced pT3/4, and nodal and metastatic N1/M1) remained the same, the researchers note.
As the major revision in the 2010 TNM was in the T3 staging, Heer and team focused on the effect this update had on survival outcomes.
According to the 2002 TNM, Kaplan-Meier survival curves showed significant differences in overall and disease-specific survival between patients with T1 and T3b tumors, but not between those with T1 and T3a tumors.
However, when tumor stage was reassigned according to the 2010 classification, patients with T3a tumors had significantly worse overall and disease-specific survival than those with T1 tumors.
Writing in the Journal of Clinical Pathology, the researchers conclude: "Reclassification of T3 tumors using the 2010 TNM system showed better correlation with predicting worsening outcomes compared with localized disease (T1/2) in our cohort."
By Laura Cowen