Patients with cT1a renal masses have historically been shown, with treatment, to have very high cancer-specific survival – and Dr. Finelli notes that this is likely a sign of the biology rather than treatment alone. While masses < 4 cm can rarely develop or present with metastatic disease, it is very uncommon. And, unfortunately, due to the rising rates of cross-sectional imaging, the rates of small renal masses continues to increase – a recent paper by Welch et al1 demonstrated that regional variation with CT utilization was directly correlated with the number of nephrectomies.
As such, better understanding of the natural history of these small renal masses can help guide future management, as the incidence continues to rise. While not perfect, tumor size is still a good predictor of malignancy risk, with masses <4 cm having a 20% chance of being benign. Smaller tumors have a higher chance of being low-grade.
1. Before the imaging era, >50% of renal masses were diagnosed on autopsy
2. Size and stage correlate with development of metastases and outcomes
3. Tumors < 3 cm rarely metastasize
4. 20-30% of tumors <3 cm are benign
Our understanding of RCC growth kinetics began with watchful waiting in patients considered unfit for surgery – across all comes, average growth rate was 0.28 cm/year. The DISSRM study2, a non-randomized study that followed patients who elected for either intervention or surveillance for small renal masses (and could switch to intervention at any time), found that OS and CSS for both intervention and surveillance arms was very high.
The Canadian experience with AS3 found that average growth was 0.28 cm/year, but there was significant variability. Rate of metastatic spread and death was very low. Indeed, when subcategorized by histology, papillary type 1 tumors were much more indolent than ccRCC.
A systematic review by Marc Smaldone (pending publication) of 18 series (880 patients, 936 tumors) found that only 18 patients progressed to metastases (mean 40.2 months). Primary predictors were linear growth rate, tumor diameter, tumor volume, and volumetric growth rate.
Dr. Finelli does recommend that RTB be coupled with AS for all patients considering AS. The intent of AS is cure, so knowing the pathology can help guide surveillance. Patients on watchful waiting (intent is prevention of symptoms) do not need RTB.
- RTB diagnostic rate > 90% in high volume centers
- Grade concordance not as robust as histologic diagnosis
Lastly, tumor ablation is an option for patients as well, but in his experience, it is best done when:
- Tumor <= 3 cm
- Partially exophytic
- Away from adjacent organs (bowel, liver, UPJ)
- In patients who are a high general anesthetic risk
1. Strong data to support a more rational approach to the management of SRMs
2. Emerging evidence of histology-specific growth rates and prognosis to guide treatment
3. RTB can inform care
4. Initial AS is appropriate for many patients with cT1a tumors, and especially those with masses < 2 cm
5. Based on histology specific growth rates and metastatic potential, papillary type 1 and chromophobe tumors are better suited for AS
Presented by: Antonio Finelli, MD University of Toronto
Written by: Thenappan Chandrasekar, MD, Clinical Fellow, University of Toronto | @tchandra_uromd at the 2018 American Society of Clinical Oncology Genitourinary (ASCO GU) Cancers Symposium, February 8-10, 2018 - San Francisco, CA
1. Welch HG et al. Regional Variation of Computed Tomographic Imaging in the United States and the Risk of Nephrectomy. JAMA Intern Med. 2018 Feb 1;178(2):221-227. doi: 10.1001/jamainternmed.2017.7508.
2. Uzosike AC, Patel HD, Alam R, Schwen ZR, Gupta M, Gorin MA, Johnson MH, Gausepohl H, Riffon MF, Trock BJ, Chang P, Wagner AA, McKiernan JM, Allaf ME, Pierorazio PM. Growth Kinetics of Small Renal Masses on Active Surveillance: Variability and Results from the DISSRM Registry. J Urol. 2017 Sep 23. pii: S0022-5347(17)77614-8. doi: 10.1016/j.juro.2017.09.087. [Epub ahead of print]
3. Jewett MA, Mattar K, Basiuk J, Morash CG, Pautler SE, Siemens DR, Tanguay S, Rendon RA, Gleave ME, Drachenberg DE, Chow R, Chung H, Chin JL, Fleshner NE, Evans AJ, Gallie BL, Haider MA, Kachura JR, Kurban G, Fernandes K, Finelli A. Active surveillance of small renal masses: progression patterns of early stage kidney cancer. Eur Urol. 2011 Jul;60(1):39-44. doi: 10.1016/j.eururo.2011.03.030. Epub 2011 Apr 1.
4. Finelli A, Ismaila N, Bro B, Durack J, Eggener S, Evans A, Gill I, Graham D, Huang W, Jewett MA, Latcha S, Lowrance W, Rosner M, Shayegan B, Thompson RH, Uzzo R, Russo P. Management of Small Renal Masses: American Society of Clinical Oncology Clinical Practice Guideline. J Clin Oncol. 2017 Feb 20;35(6):668-680. doi: 10.1200/JCO.2016.69.9645. Epub 2017 Jan 17.