What is the recommended treatment approach for a patient with a renal mass?

Management of Renal Masses

For patients with a renal mass, partial nephrectomy is the first-line treatment for cT1a lesions (≤4 cm) when intervention is indicated, while active surveillance is an acceptable initial option for small masses (<2 cm), especially in patients where competing risks of death outweigh oncologic benefits. 1, 2

Initial Diagnostic Workup

Obtain high-quality multiphase cross-sectional imaging (CT or MRI with and without contrast) to characterize the mass, assess enhancement patterns, detect fat content, and clinically stage the lesion. 1, 2 This imaging must evaluate:

• Tumor complexity and degree of contrast enhancement 1
• Presence or absence of fat 1
• Locally invasive features and venous involvement 2
• Contralateral kidney status 2

Obtain comprehensive metabolic panel, complete blood count, and urinalysis for all patients. 1 If malignancy is suspected, obtain chest imaging to evaluate for thoracic metastases. 1, 2

Assign CKD stage based on GFR and degree of proteinuria before treatment planning. 1 This is critical because radical nephrectomy increases risk of CKD, which correlates with increased cardiovascular morbidity and mortality. 2

Role of Renal Mass Biopsy

Perform renal mass biopsy in three specific scenarios: 2

• Prior to all thermal ablation procedures (mandatory) 1, 2
• When clinical/radiographic findings suggest lymphoma, abscess, or metastasis 2
• For indeterminate masses where histological diagnosis would alter management 2

Do not perform biopsy on purely cystic lesions (Bosniak 2F) due to low diagnostic yield. 3

Treatment Algorithm by Tumor Size and Stage

cT1a Renal Masses (≤4 cm)

Prioritize partial nephrectomy as first-line intervention when treatment is indicated. 1, 2 Partial nephrectomy is greatly underutilized and often feasible even for central/hilar tumors with adequate expertise. 2

Consider thermal ablation as an alternate approach for masses <3 cm, with percutaneous technique preferred over surgical approach. 1 Both radiofrequency ablation and cryoablation are acceptable options. 1 However, counsel patients that thermal ablation has higher local recurrence rates compared to partial nephrectomy when analyzing only primary treatment, though differences largely disappear when salvage therapies are considered. 1

Active surveillance is an acceptable initial option for small masses, especially <2 cm. 1 Short-term (12-36 months) cancer-specific survival rates with active surveillance exceed 95% in well-selected patients. 1 For masses where risk/benefit analysis is equivocal and the patient prefers surveillance, repeat imaging in 3-6 months to assess for interval growth and consider renal mass biopsy for additional risk stratification. 1

cT1b Renal Masses (>4-7 cm)

Partial nephrectomy remains the priority nephron-sparing approach. 2

cT3a Disease with Nodal Involvement

Open radical nephrectomy with regional lymph node dissection is the standard approach. 2

Imperative Indications for Nephron-Sparing Surgery

Prioritize nephron-sparing approaches (partial nephrectomy or thermal ablation) in the following scenarios: 1, 2

• Anatomic or functionally solitary kidney 1, 2
• Bilateral renal tumors 1, 2
• Known familial RCC syndromes 1, 2
• Pre-existing CKD (GFR <60 mL/min/1.73m²) 2
• Confirmed proteinuria 2
• Young patients 1, 2
• Multifocal masses 1, 2
• Comorbidities likely to impact future renal function (diabetes, hypertension) 1, 2

When to Prioritize Active Surveillance Over Intervention

Prioritize active surveillance/expectant management when the anticipated risk of intervention or competing risks of death outweigh the potential oncologic benefits of active treatment. 1 This applies particularly to:

• Patients with limited life expectancy 1
• Patients with significantly elevated surgical risk 1
• Patients who potentially face end-stage renal disease 1
• Elderly patients with significant comorbidities 1

Nephrology Referral Criteria

Refer to nephrology when: 1, 2

• GFR <45 mL/min/1.73m² 1, 2
• Confirmed proteinuria is present 1, 2
• Diabetics have pre-existing CKD 1, 2
• Expected post-intervention GFR <30 mL/min/1.73m² 1, 2

Genetic Counseling

Recommend genetic counseling for all patients ≤46 years of age. 1, 2 Consider genetic counseling for patients with multifocal or bilateral renal masses, or if personal/family history suggests familial renal neoplastic syndrome. 1, 2

Management of Bosniak Cystic Lesions

For Bosniak 2F cysts, perform active surveillance with repeat imaging at 6-12 months using contrast-enhanced CT or MRI. 3 These lesions carry approximately 10% malignancy risk and do not warrant immediate surgical intervention. 3 Immediate surgery would constitute overtreatment in 90% of cases. 3

For Bosniak III/IV complex cystic masses, recommend intervention when anticipated oncologic benefits outweigh risks, prioritizing nephron-sparing approaches. 4

Critical Pitfalls to Avoid

• Do not perform radical nephrectomy reflexively for cT1a masses - partial nephrectomy is often feasible even for central/hilar tumors with adequate expertise 2
• Do not skip renal mass biopsy before thermal ablation - it is mandatory 1, 2
• Do not ignore renal functional assessment - CKD staging must be performed for all patients with suspected malignancy 1, 2
• Do not initiate treatment without high-quality multiphase cross-sectional imaging - inadequate imaging leads to suboptimal management decisions 2
• Do not perform immediate surgery on Bosniak 2F lesions - this constitutes overtreatment in the vast majority of cases 3