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by Dr. C.H. Weaver M.D. updated 6/2022

Many small renal masses are incidentally discovered when a CT or MRI is performed for other reasons. These masses may be benign or a non-aggressive cancer. Patients with small renal masses must decide whether to surgically remove or ablate the mass and often undergo unnecessary treatment of these benign and potentially indolent cancers.1,2

Kidney Cancer CancerConnect Renal

Another option is to consider a program of “active surveillance.” Most small cancers grow very slowly and have a low potential to spread to other organs. Because all treatment options carry some risk, some patients with early stage renal cell cancers may want to consider a program of “active surveillance.” 

During active surveillance, the patient and their urologist agree to observe the cancer by obtaining regular imaging scans – usually some combination of MRI/ PET/CT. Using this approach some individuals may be able to avoid surgery and others, reach a “trigger for intervention” and definitive therapy is initiated. Doctors have reported the results of an active surveillance program implemented in 371 patients over a ten year period. No patients experienced metastatic progression or died of kidney cancer, however almost 50% ultimately elected to undergo definitive treatment of the mass due to anxiety.3

Who should consider surveillance?

Individuals with masses less than 2 centimeters in size are ideal candidates for active surveillance because there is a low likelihood the cancer will spread during observation. Some patients with cancers between 2-4 centimeters can also be safely watched based on a number of factors:

  • Patients with a single kidney or those with poor kidney function. Because intervention to treat the cancer can cause further deterioration of kidney function, these patients may be better off selecting active surveillance. Deterioration in kidney function puts a patient at risk of needing dialysis. Dialysis, while lifesaving, may be associated with poor outcomes and a low quality of life.
  • Patients with hereditary forms of kidney cancer - Von-Hippel-Lindau (VHL) or other conditions in which patients are at risk of having multiple tumors on both sides. These tumors are typically placed on active surveillance until they reach 3 centimeters or larger.
  • Elderly patients and those with other co-morbid medical conditions that increases the risk of intervention. Since the risk that a small kidney tumor spreads is low surveillance in individuals with a short life expectancy may be prudent. Like prostate cancer many of these patients die with the cancer rather than from the cancer.
  • Patients who do not wish to have treatment.
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Active surveillance for masses with no evidence of spread to lymph nodes or other organs consists of performing imaging of the renal mass every three to six months for two years then every six to 12 months annually. Doctors typically use CT or MRI for the initial evaluation and then alternate between CT, MRI, and ultrasound to minimize radiation exposure.

Genitourinary Cancer Newsletter 490 GU

During surveillance if the mass grows your doctor can remove the mass using surgery or other treatments. The risk of spread for a cancer less than 2 centimeters is less than 1%. The risk is 1–2% for 3-centimeter tumors and 3–5% for 4-centimeter tumors. Each patient and cancer are unique, your doctor can help you understand your individual risk and make an informed decision.