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Background: Despite an increase in the rate of detection and treatment of localized renal tumors, parallel improvements in disease-specific survival have not been observed. Since most small renal cell carcinomas (RCCs) have a low metastatic potential, surgical intervention may be unnecessary in the short-term. Given that approximately 80% of renal masses are benign or indolent, delaying surgical intervention or enrolling in active surveillance (AS) of the renal mass may also be a reasonable and viable treatment paradigm for selected patient groups. In this study, we attempted to assess patient demographics and clinical indices as indicators for the selection of treatment paradigms for small renal masses.
Methods: We retrospectively reviewed our IRB approved renal mass (RM) database and retrieved clinical, radiological and pathological records of patients who (i) underwent robotic partial nephrectomy (RPN) after diagnosis, or (ii) entered a ≥12 month period of initial surveillance. At follow up (≥12 months) these patients either ceased surveillance and underwent partial nephrectomy or cryoablation (delayed intervention-DI) or continued on active surveillance (AS). Age, sex, body mass index, Charlson Comorbidity Index, follow-up period, tumor size, tumor growth rate, creatinine, estimated glomerular filtration rate, and malignancy at diagnosis and intervention were assessed as predictors of which treatment option was selected. Renal mass growth rates were calculated using a linear regression model.
Results: Compared to patients undergoing initial surveillance, RPN patients were predominantly male, significantly younger, had elevated BMI, higher CCI, larger initial tumor size, lower creatinine and elevated eGFR. Patients who were initially under AS but subsequently opted for intervention were significantly younger at both diagnosis and intervention. While their tumors were smaller at diagnosis, tumor size at intervention was greater compared to those who continued on AS. Patients who discontinued AS had higher tumor growth rates.
Conclusions: Age, tumor size, and eGFR are predictors of treatment. BMI and comorbidities appear less critical in selecting between AS, DI, or RPN. DI seems a viable initial approach for RMs until significant growth is detected.

Active Surveillance versus Robotic Partial Nephrectomy

	Initial Surveillance	Robotic Partial Nephrectomy	P-value
Number of patients/masses	121/140	311/311	-
Gender (M/F; %)	68/72 (48.6/51.4)	203/108 (65.2/34.8)	<0.001
Age at diagnosis (years)	66.3±14.2	59.8±11.7	<0.001
BMI (kg/m2)	27.2±5.20	29.5±5.50	<0.001
CCI score	5.3±2.1	3.1±1.6	<0.001
Initial Tumor Size (cm)	2.1±1.4	3.0±1.2	<0.001
Initial eGFR (ml/kg/1.73 m2)	67.6±20.1	78.3±19.1	<0.001

Active Surveillance versus Delayed Intervention

	Active Surveillance	Delayed Intervention	P-value
No. patients/masses	112/126	9/14	-
Gender (M/F; %)	61/65 (49.4/51.6)	5/4 (55.6/44.4)	0.88
Initial age (years)	67.1±13.6	58.4±17.7	0.046
Final age (years)	70.8±14.0	62.6±16.3	0.045
Initial Tumor size (cm)	2.1±1.4	1.7±0.5	0.02
Final Tumor size (cm)	2.3±1.7	2.8±0.7	0.02
Tumor growth rate (cm/year)	0.08±0.3	0.26±0.13	<0.001

Delayed Intervention versus Robotic Partial Nephrectomy

	Delayed Intervention	Robotic Partial Nephrectomy	P-Value
No. patients/masses	9/14	311/311	-
Initial Age (years)	58.4±17.7	58.8±11.7	0.4
Gender (M/F; %)	5/4 (55.6/44.4)	203/108 (65.2/34.8)	0.2
CCI score	5.4±2.4	3.1±1.6	0.002
Initial Tumor size (cm)	1.7±0.5	3.0±1.2	<0.001
Malignancy (%)	92.30%	81.90%	0.33