Ablative treatments are believed to have a lower rate of complications, shorter hospital stays, and fewer interventions with benign PAD compared to partial nephrectomies in small kidney cancer lesions. The purpose of the study is to compare complications, the frequency of residual tumors, impact on kidney function, differences in quality of life, and health economic factors in a randomised study. We will also compare the oncological outcomes, including survival and recurrence of kidney cancer.

Kidney cancer represents approximately 2-3% of all cancer cases, with about 400,000 new cases and 175,000 deaths worldwide in 2018. In Sweden, about 1,200 new cases of kidney cancer are detected each year. The most common age for diagnosis is between 60 and 80 years, and it is more prevalent in men than in women. Many cases are incidentally discovered during imaging studies for unrelated issues. There has been an increase in incidentally detected tumors in Sweden, from 43% in 2005 to 69% in 2021. Nephron-sparing surgery, i.e., partial nephrectomy, is recommended for preserving kidney function in localized tumors.

Ablative treatments are recommended for patients with significant comorbidities, multiple tumors, a single kidney, or other situations where surgery is not considered suitable. Prior to treatment, a biopsy is usually performed to confirm the diagnosis. Studies show variations in oncological outcomes based on the subgroups of kidney cancer treated with ablative techniques. Ablative techniques seem to have a lower risk of complications compared to surgery concerning perioperative complications, bleeding, and maintaining kidney function for a longer time. However, there are no randomized controlled studies comparing ablative treatment with nephrectomy for T1a tumors in the kidney.

3. Hypothesis

Ablative treatment of small kidney tumors may result in shorter hospital stays with fewer complications compared to surgical resection.

There is no difference in long-term oncological outcomes between the methods.

4. Outcome Measures

The primary purpose of the study is to compare surgical complications, findings of remaining tumors after primary treatment, and the time patients are hospitalized after each procedure. Secondary outcomes include oncological outcomes in the short and long term, as well as functional factors

Inclusion Criteria:

• Age 18 - 99 years
• Patient suitable based on clinical status for both ablative treatment and surgery
• Primary kidney tumor
• Tumor size ≤ 3 cm
• Clinical stage of the tumor T1a (no macroscopic vascular or extrarenal invasion)
• Tumor location suitable for both ablative treatment and resection
• Absence of radiological signs of metastasis
• Biopsy with malignant pathological analysis (PAD)
• ISUP grade I-III"

Exclusion Criteria:

• Radiological signs of metastasis
• Synchronous kidney tumors
• ISUP grade IV or sarcomatoid growth in the biopsy
• Other metastasized cancer in the last 5 years
• Patient unable to make an informed decision to participate in the study