AUA 2019: Proposal for Tripartite Reclassification of Ct1 RCC into Ct1a, Ct1b, and Ct1c Substages
Utilizing a multicenter, retrospective cohort approach, the authors identified patients with cT1 RCC who underwent partial or radical nephrectomy at one of four academic institutions (UCSD, Emory, Fox Chase Cancer Center, Ospadele San Raffaele). They categorized these patients into three groups on the basis of tumor size: very low risk (≤2cm, putative new cT1a), low risk (2-5cm, putative new cT1b), and intermediate risk (5-7cm, putative new cT1c). They then assessed the prognostic importance of this new categorization by assessing recurrence free survival and overall survival.
Among 4710 identified patients in their cohort, 856 fit the new definition of cT1a, 2909 fit the new definition of cT1b, and 945 fit the new definition of cT1c. Not surprisingly, total R.E.N.A.L. scores, indicating tumor complexity, increased with increasing tumor size with a mean R.E.N.A.L. score of 6.5 for patients with newly defined cT1a disease, 7.6 for patients with newly defined cT1b disease, and 9.0 for patients with newly defined cT1c disease (p<0.001). Mean patient age also increased with increasing tumor size.
The authors identified differences in five-year recurrence free survival on the basis of their new cT1 subclassifications: 95.7% in patients with cT1a tumors, 90.8% in patients with cT1b tumors, and 80.8% in patients with cT1c tumors (p<0.001). A similar effect was found for overall survival.
Following multivariable regression using Cox proportional hazards models, increasing tumor stage remained an important predictor of recurrence free survival (cT1b HR 1.93, p=0.002; cT1c HR 3.69, p<0.001; compared to cT1a) and overall survival (cT1b HR 1.10, p=0.44; cT1c HR 1.75, p<0.001; compared to cT1a).
Interestingly, patients with the newly defined cT1a and cT1b have similarly prognoses with significant differences between these two and cT1c. This closely mirrors the current dichotomous substratification, with the current cT1b (tumors 4-7cm) very closely overlapping the proposed cT1c (tumors 5-7cm). Further, given that cancer specific survival remains very high for patients with cT1 RCC, it is unclear whether difference in overall survival relate to meaningful differences in oncologic outcomes or residual confounding. Assessment of cancer-specific survival would shed some light on that.
While the authors demonstrate that substratification of cT1 RCC continues to provide prognostic information, there is no comparison provided with the current dichotomous substratification. Further, management rarely differs for patients on the basis of T1 substratification. Thus, it is unclear how adoption of this new categorization would affect clinical practice.
Presented by: Aaron Bradshaw, BS, US San Diego School of Medicine
Co-authors: Umberto Capitanio, Robert Uzzo, Dattatraya Patil, Ahmed Eldefrawy, Alessandro Larcher, Shreyas Joshi, Stephen Ryan, Margaret Meagher, Brittney Cotta, Addison Yee, Fang Wan, Francesco Montorsi, Viraj Master, Ithaar Derweesh
Written by: Christopher J.D. Wallis, Urology Resident, University of Toronto, @WallisCJD at American Urological Association's 2019 Annual Meeting (AUA 2019), May 3 – 6, 2019 in Chicago, Illinois