Reassessment of the 1997 TNM classification system for renal cell carcinoma

The 1997 TNM staging classification for renal cell carcinoma (RCC) defined Stage I tumors as organ-confined tumors measuring up to 7 cm in size. The authors evaluated the validity of this cutoff size by assessing the survival of patients with Stage I RCC according to a series of alternative size cutoff values. In addition, the authors determined how these size cutoffs affected the risk of having nonorgan-confined tumors, regional lymph node involvement, and metastatic disease.

A database containing the records of 1324 patients with RCC who underwent open radical nephrectomy between 1960 and 1991 was evaluated. Patients with Stage I disease were stratified by size cutoffs ranging from 2.5 to 7.0 cm in 0.5-cm increments. Five-year disease-specific survival (DSS) rates were estimated using the Kaplan-Meier method. The log-rank test was used to compare survival curves. The survival of patients with tumors smaller than a specified size cutoff was compared with the survival of patients with tumors larger than that cutoff and the most discriminating cutoff was identified. The same size cutoffs were used to compare the incidence of local nonorgan-confined, lymph node-positive, and metastatic disease for all patients with tumors 7.0 cm or smaller.

Of 544 evaluable patients, 351 patients had tumors 7.0 cm or smaller and 233 of these patients had 1997 Stage I (T1N0M0) disease. When patients with 1997 Stage I tumors were separated using the various size cutoffs, survivals were most different using a 5.0-cm cutoff. The 5-year DSS rates for patients with Stage I tumors 5 cm or smaller versus those with tumors measuring 5.1-7 cm were 94.6% versus 79.2% (P = 0.003). Furthermore, the survival of patients with Stage I RCC lesions measuring 5.1-7.0 cm was the same as for patients with 1997 Stage II (T2N0M0) RCC. The difference in probability of having local nonorgan-confined disease was also greatest with a 5.0 cm cutoff value. Nonorgan- confined disease was reported to be present in 16.2% of the patients with tumors smaller than 5.0 cm compared with 36.8% of the patients with tumors measuring 5.1-7.0 cm in size. The difference in the probabilities of having lymph node-positive or metastatic disease did not change significantly using any of the cutoffs, although the probability of both of these increased with increasing tumor size.

Survival and disease recurrence analysis in a large group of patients with RCC who underwent radical nephrectomy showed that the 1997 TNM cutoff of 7.0 cm used to separate Stage I from Stage II disease was too high. A size-related survival difference was found among patients with organ-confined 1997 Stage I disease and a 5.0-cm cutoff best stratified this difference. This finding was in general agreement with the changes made in the 6th edition of the American Joint Committee on Cancer cancer staging manual. Patients with tumors measuring between 5.1 cm and 7.0 cm were found to have the same survival as patients with Stage II disease. Thus, subclassification of T1 into T1a and T1b, as in the 6th edition of the AJCC cancer staging manual, may not be optimal. The 5-cm cutoff also best stratified the risk of developing nonorgan-confined disease. This finding may have an impact on nephron-sparing surgery in selected patients. The findings of the current study, as well as those of others, supported an upper size cutoff of 4-5 cm for patients with Stage I RCC.