Introduction:

With the widespread adoption of cross-sectional imaging, the incidence of small renal masses has risen, leading to earlier detection of renal cell carcinoma (RCC), with clinical stage T1a RCC (tumors ≤4.0 cm) accounting for 40% of new RCC cases. While radical nephrectomy was historically the gold standard, concerns about long-term renal function have led to nephron-sparing approaches like partial nephrectomy (PN). Thermal ablation (TA)—including cryoablation and radiofrequency ablation—has emerged as a minimally invasive alternative, particularly for older or comorbid patients. Guidelines recommend considering TA for tumors <3.0 cm, but selection criteria remain vague, and population-level data comparing oncologic outcomes with surgery are limited. Moreover, treatment disparities may limit equitable access to TA. This study aims to characterize national trends in TA, PN, and radical nephrectomy (RN) for T1a RCC and evaluate long-term overall and cancer-specific survival (CSS) using the SEER database from 2004–2022.

Methods:

We identified patients with clinical T1a (≤4.0 cm) RCC diagnosed between 2004 and 2021 using the SEER database. Patients were stratified by initial treatment: TA, PN, RN, or observation. Descriptive statistics were used to compare baseline demographic and tumor characteristics across groups. Categorical and continuous variables were compared using chi-squared and t-tests or Wilcoxon rank-sum tests, respectively. Multivariable logistic regression identified factors associated with TA utilization relative to surgical treatment (PN and RN). Kaplan-Meier survival analysis was used to estimate 10-year overall survival (OS) and cancer-specific survival (CSS). Cox proportional hazards regression was used to identify predictors of cancer-specific mortality. Key covariates included age, sex, race, tumor size, tumor grade, histology, marital status, and year of diagnosis. SEER limitations—such as lack of comorbidity, renal function, recurrence, and re-treatment data—were considered when interpreting treatment selection and survival outcomes.

Results:

Among 68,048 patients with T1a RCC, utilization of TA increased from 3.4% to 14% during the study period, concurrent with rising PN and declining RN rates. Patients undergoing TA were older (median 67 years), had smaller tumors (median 2.5 cm). TA was more likely among older patients (OR 1.1 per year, p<0.0001), with smaller tumors (OR 0.80, p<0.0001), and later year of diagnosis (OR 1.1, p<0.0001). African American (OR 0.79), female (OR 0.85), married (OR 0.81), and urban-dwelling patients (OR 0.83) were less likely to receive TA. Ten-year CSS was highest for surgery (97%), followed closely by TA (96%) and lower for observation (82%, p<0.001). OS differed more substantially: surgery (78%), TA (61%), and observation (30%). On multivariable analysis, CSS did not significantly differ between TA and surgery (HR 1.3, p=0.074), but was significantly worse for observation (HR 4.4, p<0.0001).

Conclusion:

This large, population-based study demonstrates increasing national use of TA and nephron-sparing surgery for T1a RCC, with concurrent declines in RN. We report the longest follow-up of TA to date, showing that CSS after TA approaches that of surgery in appropriately selected patients, although OS is lower, reflecting baseline health differences. While prior studies suggested inferior oncologic outcomes with TA, our findings emphasize the importance of context: the absolute difference in 10-year CSS between surgery and TA was only 1%, versus a 17% difference in OS. TA serves a vital role for patients unfit for surgery. Significant disparities in TA use by race and sex must be further evaluated. Our findings also validate current guidelines favoring TA for smaller tumors and older patients. Limitations of SEER, including lack of comorbidity and recurrence data, must be considered. Further studies should refine selection criteria and address barriers to equitable TA adoption.

Funding: N/A