Incidental detection of small kidney tumors has risen dramatically over the past several decades due to increasing use of diagnostic imaging. In the past, surgery was the standard approach to managing all of these lesions, but recent research suggests that many small, incidentally discovered tumors do not become aggressive; therefore, in select patients, these small masses can be safely managed through an initial period of observation or active surveillance.

Small Kidney Tumors Pose Low Risk of Mortality

A clinical update was published in the April 23/30, 2019, issue of JAMA, describing investigations by William C. Huang, MD, associate professor in the Department of Urology, chief of the urology service at Tisch Hospital, and co-director of the Robotic Surgery Center at NYU Langone, and others. According to their research, small tumors measuring 4 cm or less—which are often found during imaging for other problems—pose very low risk of mortality from kidney cancer. Dr. Huang, part of NYU Langone’s Perlmutter Cancer Center and a pioneer in developing the most effective minimally invasive surgical approaches to managing kidney cancer, and his colleagues note that while 75 to 80 percent of small lesions ultimately prove to be malignant, the remaining 20 to 25 percent are actually benign. Although less than 5 percent of the small malignant tumors will metastasize at this size, treatment is still currently recommended because imaging and even biopsy provide limited information as to which tumor will ultimately become life-threatening.

Active Surveillance Is as Effective as Initial Management Strategy

Dr. Huang and colleagues point to recent evidence supporting active surveillance as an effective initial management strategy for many patients. For example, the Delayed Intervention and Surveillance for Small Renal Masses (DISSRM) Registry reported a 100 percent cancer-specific survival rate over 5 years for patients under active surveillance. Another large review published in Cancer reported metastatic disease rates of only 1 to 2 percent for patients managed with active surveillance for 2 to 3 years. “The low risk posed by small kidney lesions suggests that these tumors can be managed similarly to low-risk prostate cancer, which also frequently has an indolent or ‘lazy’ course,” says Dr. Huang.

Individualized Treatment Plans and Shared Decision-Making

Management of small tumors should be individualized to each patient, advises Dr. Huang. Factors to consider when creating a treatment plan include the risk of mortality from kidney cancer, mortality risk from comorbid conditions, and the potential for treatment-related side effects. The most recent American Urological Association clinical guidelines endorse an initial period of active surveillance instead of treatment as an option for small lesions measuring less than 2 cm. The guidelines caution that patients should be fully informed about the low risk of cancer-specific mortality for very small lesions, in the absence of comorbid conditions, and also be given the option to pursue biopsy when warranted.

Decisions about whether to pursue surgery versus surveillance should take into account the overall health and anticipated longevity of the patient. In addition, tumor characteristics such as location may also play a role in decision-making as the treatment may unnecessarily result in loss of kidney function. In patients with small renal masses and significant comorbid conditions or significant preexisting chronic kidney disease, any surgical treatment (including partial) may negatively impact their kidney function, their quality of life, or both.

While active surveillance is emerging as a safe and effective option for select patients with very small tumors, evidence from randomized trials is lacking, Dr. Huang notes. As a result, physicians should fully inform patients about the potential risks and benefits of various treatment options and engage them in shared decision-making.

“In the future, we hope to develop new tests so that we can accurately identify tumors which are not safe to observe,” says Dr. Huang. “However, for now, we can help patients fully understand the low mortality risk associated with many of these small tumors so that they are enabled to make an informed decision as to whether they want to pursue treatment for their small renal mass.”

Disclosure: William C. Huang, MD, reported membership on the American Society of Clinical Oncology Guidelines Panel for Small Renal Masses.