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BACKGROUND: 2009 AJCC prostate cancer staging subclassifies T2 cancer into 3 subcategories. T2a tumors occupy one half or less of one lobe, T2b tumors occupy more than one half of a lobe, while T2c tumors involve both lobes. The validity, prevalence and prognostic significance of T2b stagingis under debate. We examine the incidence, positive margin rates, and mean months to biochemical recurrence for clinical and pathologic T2 prostate cancer.
METHODS: Our IRB approved, prospectively maintained robotic radical prostatectomy database was retrospectively examined. Patients who underwent surgery from January 1, 2004-December 31, 2011 were included. Clinical and pathologic T2 prostate cancer was identified. Corresponding margin positive rates and mean months to biochemical recurrence were determined. Univariate analysis was performed using SPSS v 14.0(SPSS, Inc., Chicago, IL, USA.). Kaplan Meier curves were generated to determine months to biochemical recurrence and statistical significance was determined with log rank testing. P values <0.05 were considered significant and adjusted when appropriate using the Bonferroni method.
RESULTS: 2,687 patients underwent surgery during this time period. There were 295 cT2a, 158 cT2b, 24 cT2c, and 25 cT3a prostate cancers. There were 178 pT2a, 37 pT2b, and 1,354 pT2c prostate cancers. The positive margin rates for cT2a, cT2b, cT2c, and cT3a were 20.1%, 32.5%, 25.0%, and 45.8% respectively while the mean months to biochemical recurrence were 69.2, 54.2, 37.7, and 30.2 (Table 1). The positive margin rates for pT2a, pT2b, and pT2c were 7.5%, 18.9%, and 16.5%, respectively while the mean months to biochemical recurrence were 74.9, 55.0, and 77.5 (Table 2).
CONCLUSIONS: Gleason score, positive margin rates, and biochemical recurrence differ significantly among the substages of cT2 prostate cancer. However, there were no significant differences between the Gleason score, positive margin rates, and biochemical recurrence of pT2b and pT2c prostate cancers. These findings, coupled with the low incidence of pT2b cancers, support the elimination of pT2b substaging.

Table 1

	cT2a	cT2b	cT2c	cT3a	P Value
# Cases	295	158	24	25
# Cases (% Total) pGleason 6 pGleason 7 pGleason 8-10	22.1% 70.7% 7.1%	12.7% 68.4% 19.0%	0.0% 87.5% 12.5%	0.0% 50.0% 50.0%	p<0.001
# Cases (% Total) pT0 pT2a pT2b pT2c pT3a pT3b pT4	0.7% 11.2% 1.7% 60.0% 21.0% 5.1% 0.3%	0.0% 1.3% 0.6% 46.2% 39.2% 12.7% 0.0%	0.0% 0.0% 0.0% 54.2% 37.5% 8.3% 0.0%	0.0% 0.0% 0.0% 16.7% 58.3% 25.0% 0.0%	p<0.001
Positive Margin	20.1%	32.5%	25.0%	45.8%	p=0.003
Mean Months to Recurrence	69.2	54.2	37.7	30.2	p<.001

Table 2

	pT2a	pT2b	pT2c	P Value
# Cases	178	37	1354
# Cases (% Total) pGleason 6 pGleason 7 pGleason 8-10	55.6% 41.6% 2.8%	29.7% 59.5% 10.8%	31.9% 64.8% 3.2%	p<0.001a
Positive Margin	7.5%	18.9%	16.5%	p=0.007b
Mean Months to Recurrence	74.9	55.0	77.5	N.S.

a-Using the Bonferroni method which results in a significant p value of p< 0.017, Gleason score differed significantly between pT2a/pT2b and pT2a/pT2c but not between pT2b/pT2c
b- Using the Bonferroni method which results in a significant p value of p< 0.017, margin rates differed significantly between pT2a/pT2b and pT2a/pT2c but not between pT2b/pT2c