Editorial Note: In recent years, numerous breakthroughs have been made in the field of renal tumors. The EAU Guidelines Panel continually incorporates new research data and evidence-based medicine to revise and update the EAU guidelines. At the 39th Annual European Association of Urology (EAU24) Congress held in Paris, France, “Oncology Frontier” invited Dr. Ruiyi Deng from Professor Kan Gong’s team at Peking University First Hospital to discuss the redefinition of small renal masses (SRMs) and the value of active surveillance.

Oncology Frontier: The EAU Guidelines Panel proposes redefining small renal masses (SRMs), reducing the cT1a threshold from 4 cm to 3 cm. Can you share your views on the diagnosis and treatment of small renal masses in light of the latest research presented at this congress?

Professor Kan Gong and Dr. Ruiyi Deng: The determination of tumor staging thresholds is based on factors such as tumor biological behavior, prognosis risk stratification, and treatment strategies. Over the past decade, the TNM staging system for renal cell carcinoma (RCC) has seen only minor adjustments. However, significant breakthroughs and advancements have been made in RCC treatment, particularly for locally advanced and metastatic RCC patients. This suggests that the current TNM staging system may no longer fully meet the needs of daily clinical practice, making an update crucial for proper risk stratification and improving its applicability in clinical settings .

This proposal stems from several related studies. One cohort study used 3 cm as the threshold, finding significant differences in 10-year cancer-specific mortality rates between tumors <3 cm and >3 cm (13.6% vs. 31.3%) . This indicates that stricter tumor control may be necessary for small renal masses to improve patient outcomes.

At this year’s EAU Congress, a retrospective study from Italy (abstract A0467) reported on this new TNM staging. The study divided 108 patients treated between 2008 and 2022 into three groups: Group A (<2 cm), Group B (2-3 cm), and Group C (>3 cm). The 5-year progression rates were 25.8%, 24.5%, and 48.6%, respectively. The median PFS exceeded 120 months for Groups A and B but was only 67 months for Group C. This indicates significant differences in prognosis between cT1a and cT1b patients under the new staging system, demonstrating its superior risk stratification capability.

In clinical practice, management of small renal masses includes active surveillance (AS) or primary intervention (PI) such as surgery or radiofrequency ablation. The debate over the survival outcomes of AS or delayed intervention versus immediate surgery continues. The aforementioned Italian study included patients on active surveillance with a minimum follow-up of six months and reported no tumor metastasis or cancer-related deaths, suggesting that AS is relatively safe for such patients.

Additionally, a prospective comparative study from the United States, DISSRM (A0474) , reported 14-year follow-up results, including 958 cT1a patients with a median follow-up of 4.73 years. Of these, 377 (39.35%) received PI, and 581 (60.65%) underwent AS (with delayed intervention allowed). Results showed no significant difference in 12-year cancer-specific survival (CSS) between the PI and AS groups (99.3% vs. 99.8%, log-rank P=0.43). Although overall survival (OS) was significantly higher in the PI group at 3, 6, 9, and 12 years (log-rank P<0.001), there was no significant difference in tumor control.

DISSRM, the largest global prospective comparative study with the longest follow-up, shows AS is not inferior to PI. Tumor growth rate (GR) emerged as a predictor for delayed intervention during AS, as increased GR correlated with more delayed interventions. Clinically, balancing tumor control with kidney function preservation is critical. Aggressive intervention should be avoided unless necessary, considering patient tolerance and potential postoperative quality of life impact. Conversely, over-conservatism should also be avoided, as delaying treatment may lead to tumor progression. The key is to determine the optimal intervention timing, especially if malignancy is confirmed or highly suspected based on rapid tumor growth or malignancy features on imaging.

Oncology Frontier: Besides observing tumor size changes through imaging, can renal biopsy also be an evaluation method during the active surveillance of small renal masses?

Professor Kan Gong and Dr. Ruiyi Deng: The kidney is located retroperitoneally, making biopsy technically challenging with risks of bleeding, infection, and urine leakage. Therefore, renal tumor biopsies are not routinely performed. Small renal masses may not show typical imaging features of RCC, making it challenging to differentiate from benign tumors. A biopsy may be necessary to clarify pathology and guide treatment plans.

Improvements in imaging technology have enhanced the feasibility and safety of renal biopsies, making them increasingly important for small renal masses. The European Modified Delphi Consensus Statement (abstract A0460) reported at this EAU conference showed that 80% of experts believe all small renal masses (<4 cm) should be biopsied before surgery or ablation, 83% support biopsy before AS to develop individualized follow-up plans, and 84% recommend biopsy if significant tumor growth is observed during surveillance.

Another study from the United States (abstract A0466) analyzed 4777 cT1a patients on AS from the National Cancer Database (NCDB) from 2004-2020. Among them, 1364 (28.5%) underwent biopsy, and 3413 (71.5%) did not. Cox regression analysis showed that the biopsy group had significantly improved survival (HR 0.86, 95% CI: 0.79-0.93, P<0.001), indicating biopsy as a prognostic tool for small tumors, optimizing AS plans. However, the risk of tumor seeding and spread should be considered. We have encountered cases of peritoneal seeding post-biopsy, requiring vigilance. Although complications like bleeding, urine leakage, and infection have decreased with advanced techniques, further prospective studies are needed to evaluate long-term risks like tumor seeding.

Professor Kan Gong

• Deputy Director, Urology Research Institute, Peking University
• Chief Physician, Professor, Doctoral Supervisor
• Recipient of the Third Batch of “National High-level Talent Special Support Plan (Ten Thousand Talent Program)”
• Vice Chairman, Chinese Medical Promotion Association Urology Branch
• Member, Tumor Group, Chinese Medical Association Urology Branch
• Member, Rare Diseases Branch, Chinese Medical Association
• Member, Urological Tumor Committee, Chinese Medical Doctor Association
• Editor, “Chinese Guidelines for the Diagnosis and Treatment of Urological Diseases – Prostate Cancer”

Dr. Ruiyi Deng

• PhD candidate in Urology at Peking University First Hospital, mentored by Professor Kan Gong
• Published 11 academic papers, including 7 SCI papers as first or co-first author
• Hosted a Beijing Natural Science Foundation “Qiyan” project
• Oral presenter at the 2024 European Association of Urology Annual Meeting (EAU24)
• Recipient of National Scholarship, Beijing University Excellent Student Award, among other honors