Oncologic risk has been well-explored and increases with tumor size. Approximately 20% to 30% of SRMs are ultimately benign, and the threat of high-grade disease in SRMs is low (~10%-15%). Furthermore, the incidence of synchronous metastatic disease in the SRM cohort is quite low. Renal mass biopsy is safe and can be used when histologic risk assessment changes clinical management. Nomograms for patient risk have been defined considering race, sex, tumor size, age, and the Charlson comorbidity index (Kutikov et al. J Urol. 2012;188:2077) and can be used at the point of service using website-based calculators (www.cancernomograms.com). Procedural-risk calculators are also available through the National Surgical Quality Improvement Program, and they demonstrate that patient risk drives outcomes more than procedural risk. Thus, the appropriate question ought to be “Should the high-risk patient have surgery?” rather than “What kind of surgery should the high-risk patient have?”
Linear growth rate (LGR) is the primary driver for delayed intervention on SRMs being followed expectantly. The mean LGR ranges from 0.07 to 0.86 cm/year, and zero net-growth rates range from 2.7% to 73% according to the literature. There is a large span of progression to definitive treatment (4%-65%), and the rate of metastasis in well-conducted studies is low (1%-2%).
Dr. Smaldone highlighted current prospective trials in AS for SRM space. Three are currently accruing, including the Renal Cell Carcinoma Consortium of Canada, the Delayed Intervention and Surveillance for Small Renal Masses or DISSRM registry (Johns Hopkins), and NCT02204800 and early outcomes from the first and second trials have been reported. Importantly, patient-reported outcomes from the DISSRM Trial have revealed that mental health is not adversely affected in patients on AS.
In summary, tumor size predicts malignant potential, high-grade disease, and the threat of metastases. Tumors smaller than 3 cm are most likely low-grade tumors, with 20% to 30% of them being benign. Most elderly comorbid patients with SRMs are destined to die of other causes. An initial period of AS to determine tumor growth kinetics and best select candidates for delayed intervention is a reasonable strategy with intermediate follow-up. A substantial proportion of SRMs exhibit zero net growth over time; even benign masses grow, and lesions exhibiting growth kinetics may be the most appropriate candidates for renal mass biopsy. LGR is currently the most reliable indicator of delayed intervention. Ideal candidates for prolonged AS are tumors smaller than 3 cm that show minimal growth over time (a very low risk of metastasis). Finally, treatment options are not limited in patients who progress to definitive intervention. Since randomized, controlled trials are unlikely to be forthcoming, prospective registries will guide best practice for AS in SRMs as their data mature.
Presenter: Marc Smaldone, MD, MSHP, Fox Chase Cancer Center, Temple University Health System
Written By: Benjamin T. Ristau, MD, Society of Urologic Oncology Fellow, Fox Chase Cancer Center
at the 2017 Genitourinary Cancers Symposium - February 16 - 18, 2017 – Orlando, Florida USA