How to treat a Small Renal Mass with Potentially Aggressive Features

Small renal masses (SRMs) include solid, cortical tumors less than 4cm that are confined to the kidney (AJCC clinical tumor stage, cT1a).  The majority of these tumors are cured with partial nephrectomy or can be safely monitored in an active surveillance program.  However, when removed some can demonstrate aggressive features (like invasion into the fat or blood vessels surrounding the kidney, AJCC pathological tumor stage, pT3a) and have a higher risk of recurrence or death from kidney cancer.  Occasionally, patients will have a CT scan or MRI that indicates that their SRM is touching the sinus fat and ask in clinic, does that mean it is aggressive and I am not a candidate for active surveillance?  Here we review the data about SRM with potentially aggressive features.

Michael Gorin, MD

SRMs pose a management quandary as they are a biologically heterogeneous group of tumors.  Surgical series demonstrate benign pathology in 20-30% of SRMs, and for those lesions that are cancerous, the majority are low-grade and unlikely to develop metastases.[1-3]  While a statistical minority, the tumors with aggressive features account for the majority of deaths from renal cell carcinoma (RCC) in the SRM population. 

Mohamad E. Allaf, MD

Michael Gorin, MD, a resident at the Brady Urological Institute at Johns Hopkins Hospital working with Mohamad Allaf, MD, Associate Professor of Urology, Oncology, and Biomedical Engineering, and Director of Minimally Invasive and Robotic Surgery, recently evaluated a multi-institutional database of five, high-volume, academic centers performing robotic partial nephrectomy.  In a study involving over 1,000 surgically removed renal masses, they found that 5% of clincally-localized (cT1a) tumors had aggressive features when removed and were upstaged to pT3a. Of the patients that remained cT1a, <1% had a recurrence at 2 years, while 8.2% of patients upstaged to pT3a had a recurrence of cancer over the same time period (see figure).      

 

Drs. Gorin and Allaf then looked to see if imaging characteristics prior to surgery were predictive of upstaging.  They found that increasing tumor size and tumors close to the renal hilum were independent risk factors for upstaging from cT1a to pT3a.  


Therefore, they drew a number of conclusions from this data:

• It is rare for a small renal tumor to actually be invasive and simply touching the fat on imaging does not necessarily mean it is invading it.

• Patients with small renal tumors touching the sinus fat are still candidates for active surveillance understanding that larger tumors that are hilar (close to the kidney blood vessels) are more likely to be invasive .  

• For these tumors, we typically advocate a more aggressive approach.

Read the entire manuscript:
Gorin MA, Ball MW, Pierorazio PM, Tanagho YS, Bhayani SB, Kaouk JH, Rogers CG, Stifelman MD, Khalifeh A, Kumar R, Sivarajan G, Allaf ME.Outcomes and predictors of clinical T1 to pathological T3a tumor up-staging after robotic partial nephrectomy: a multi-institutional analysis.J Urol. 2013 Nov;190(5):1907-11. doi: 10.1016/j.juro.2013.06.014. Epub 2013 Jun 11.
http://www.sciencedirect.com/science/article/pii/S0022534713045849

This blog entry was written in part by Mohamad E. Allaf, MD, Associate Professor of Urology, Oncology, and Biomedical Engineering, and Director of Minimally Invasive and Robotic Surgery.

[1]  Kutikov A, Fossett LK, Ramchandani P, Tomaszewski JE, Siegelman ES, Banner MP, Van Arsdalen KN, Wein AJ, Malkowicz SB.Incidence of benign pathologic findings at partial nephrectomy for solitary renal mass presumed to be renal cell carcinoma on preoperative imaging.Urology. 2006 Oct;68(4):737-40.
[2] Rothman J, Egleston B, Wong YN, Iffrig K, Lebovitch S, Uzzo RG.Histopathological characteristics of localized renal cell carcinoma correlate with tumor size: a SEER analysis.J Urol. 2009 Jan;181(1):29-33; discussion 33-4. doi: 10.1016/j.juro.2008.09.009. Epub 2008 Nov 13.
[3] Thompson RH, Hill JR, Babayev Y, Cronin A, Kaag M, Kundu S, Bernstein M, Coleman J, Dalbagni G, Touijer K, Russo P.Metastatic renal cell carcinoma risk according to tumor size.J Urol. 2009 Jul;182(1):41-5. doi: 10.1016/j.juro.2009.02.128. Epub 2009 May 17.