Almost 100% of patients with small kidney tumors never developed advanced cancer or died of the disease during more than 4 years of follow-up in active surveillance.
More than half of the mostly older patients remained alive without metastatic disease at last follow-up. Two of 103 patients developed metastatic disease, one of whom died of kidney cancer.
Fewer than 20% of patients underwent definitive treatment, half of whom did so because of patient preference, not changes in disease status, Ricardo Rendon, MD, of Dalhousie University in Halifax, Nova Scotia, and co-authors reported in the Journal of Urology.
“At a median follow-up of close to 5 years, most small renal masses in patients on active surveillance displayed indolent behavior, and the risk of progression to metastatic disease was low,” the authors concluded. “Thus, active surveillance is a safe treatment option in patients at high risk for the morbidity of active treatment. Further studies are needed to identify factors associated with disease aggressiveness and progression.”
The results are consistent with those of a Mayo Clinic surveillance program that has grown to encompass about 600 patients, said Matthew Tollefson, MD, of Mayo in Rochester, Minnesota. In particular, the Canadian study showed an annual tumor growth rate of about 2 mm, and the tumor growth rate in the Mayo program has ranged between 1 and 3 mm.
“Basically, I would say that this study is supportive of this approach that has been catching some steam to observe small renal masses,” he told MedPage Today.
“Studies like this support the importance of recognizing that the majority of these small tumors are very indolent and can be managed over quite a long period without any actual treatment,” Tollefson added.
Improved imaging techniques have increased incidental detection of small renal masses. Today more than 90% of patients have asymptomatic disease at diagnosis. Younger patients with few comorbidities often undergo partial nephrectomy, but such surgery in older patients or those with multiple comorbid conditions carries a substantial risk of morbidity, including adverse effects on renal function. Active surveillance has emerged as a preferred management strategy for many of these patients, the authors noted in their introduction.
Several studies documented the safety of active surveillance for older patients with small renal masses, but the data came primarily from small, retrospective data sets. Most current prospective studies have small sample size, limited follow-up, and little data regarding factors associated with renal mass growth and progression, the authors continued.
The Canadian group reported findings from a prospectively enrolled patient cohort with a median follow-up of 55 months in active surveillance. The 103 patients had a total of 107 renal masses. The study population had a median age of 75, median maximum mass diameter of 2.1 cm, and median maximum volume of 4.8 cm3. The small masses had a peripheral location in 70% of cases, and seven patients had symptoms suggestive of kidney cancer at diagnosis. Eleven patients had image-guided percutaneous biopsies, which revealed renal cell carcinoma (RCC) in four cases, benign masses in three, and nondiagnostic information in four.
All patients had masses suggestive of RCC on imaging. Follow-up imaging with ultrasound, computed tomography, or magnetic resonance imaging occurred at least every 6 months. The decision to discontinue active surveillance was individualized following discussion between the patient and treating physician, not because of any defined growth rate criteria.
During follow-up, 17 patients (16.5%) had active treatment, partial/radical nephrectomy in 16 cases, and radiofrequency ablation in one. One patient received treatment because of renal vein thrombus, three because of gross hematuria, and five because of tumor growth considered to represent disease progression. The remaining eight patients had treatment because of personal preference. Final pathology confirmed RCC in 12 of the 17 patients.
The authors reported that 53 patients (51.5%) remained alive without metastatic progression at last follow-up and that 48 patients (45.6%) died of causes other than kidney cancer. Annual linear and volumetric growth of the tumors averaged 0.21 cm and 6.15 cm3, respectively.
“Nearly 50% of patients in our cohort died of a competing cause throughout follow-up, indicating that active treatment would not likely have been beneficial,” the authors noted. “However, there is limited evidence on the application of active surveillance in younger and healthier patients. Although most renal masses grow slowly, during a longer time, significant changes in size could be seen, and it is likely that many patients with longer life expectancy would ultimately require treatment. Therefore, even longer follow-up is needed to clarify the role of active surveillance in young and healthy patients.”
The authors reported having no relevant disclosures.