[Reassessment of T classification system cutoff value for renal cell carcinoma].
OBJECTIVE
The 1997 T staging classification for renal cell carcinoma (RCC) defined T1 as tumors measuring up to 7 cm in size and T1 is subdivided into T1a and T1b with a 4 cm cutoff value in the 2002 TMN classification. We evaluated the validity of these cutoff values by assessing the cancer-specific survival of patients with non-metastatic RCC according to a series of alternative size cutoff values. In addition, we calculated how these size cutoffs affected the disease specific survival rates.


METHODS
A database containing the records of 200 patients with RCC who underwent open radical nephrectomy for N0M0 disease between 1985 January and 2004 January was evaluated. Tumors were stratified by cutoff values ranging from 3 to 9 cm with the 1 cm increments in order to evaluate whether the 7 cm cutoff value is appropriate. Next, T1 RCC were stratified by cutoff values ranging from 3 to 6 cm with the 1 cm increment in order to verify whether the 4 cm cutoff is appropriate. Lastly, tumors over 7 cm diameter were stratified by cutoff values ranging from 9 to 14 cm with the 1 cm increments in order to verify whether the present T2-3a categories could be divided according to tumor size.


RESULTS
As for the T1-2 classification, a cutoff value at 7 cm or 8 cm shared the greatest prognostic power. Although there was no significant difference in T1a/T1b subclassification, a 4 cm or 5 cm cutoff value resulted in a greatest separation of survival curves for T1a and T1b. As for tumors from 9-14 cm in diameter, only a 13 cm cutoff value provided a significant difference in survival.


CONCLUSIONS
Our results indicate that the present 7 cm cutoff value in the TMN system is valid in terms of prognostic value. The 4 cm cutoff value may not reflect the survival when total nephrectomy is considered, thus indicating that tumors at 4 cm cutoff value may be valid when nephron sparing surgery is considered. The 13 cm cutoff value seems to be most appropriate in N0M0 tumors with over 7 cm in diameter.
Obara
Takashi
T
Department of Urology, Akita University School of Medicine.
Matsuura
Shinobu
S
Inoue
Takamitsu
T
Kumazawa
Teruaki
T
Abe
Akihiko
A
Horikawa
Yohei
Y
Togashi
Hisahumi
H
Yuasa
Takeshi
T
Tsuchiya
Norihiko
N
Satoh
Shigeru
S
Sato
Kazunari
K
Habuchi
Tomonori
T
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002292:Carcinoma, Renal Cell / Q000145:classification / Q000401:mortality / Q000473:pathology*; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000145:classification / Q000401:mortality / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009392:Nephrectomy; D011379:Prognosis; D018570:Risk Assessment; D015996:Survival Rate