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California Statistics Indicate Kidney Cancer Rates Might Be Declining Overall

by Annette Boyle

October 16, 2017

Renal Cell Carcinoma Make Up 90% of VA’s Kidney Cancer Cases

By Annette M. Boyle

SACRAMENTO, CA — After years of apparently rising rates of kidney cancer, the incidence of early-stage disease seems to be declining, at least in California.

A study conducted at the University of California Davis and published in Kidney Cancer is the first to indicate a change in kidney cancer trends and to demonstrate significant changes in treatment.

“The increased incidence of small, localized tumors without a corresponding increase in kidney cancer deaths suggests that the incidence trends, until around 2009, were mostly driven by incidental findings associated with the increased use of advanced diagnostic imaging,” said lead author Cyllene Morris, chief epidemiologist at UC Davis’ Institute for Population Health Improvement.1

Click to Enlarge.

From 1988 to 2000, the incidence of renal cell carcinoma (RCC) nationwide rose approximately 1.5% per year, then spiked to 4.8% until 2008, after which it stabilized, the researchers found. Nearly all of the increase in RCC detected before 2008 occurred at the localized stage, with tumors of less than 4 cm.

Several studies have suggested that the apparent increase could be attributed to the sharp rise in the use of imaging. From 1996 through 2010, the number of ultrasounds performed doubled, while the number of computed tomography scans tripled and use of magnetic resonance imaging quadrupled. From 2004 to 2010, positron emission tomography scans increased 1000%, the authors noted. Since 2010, the use of imaging has largely leveled off and actually declined among privately-insured patients.Kidney cancers, primarily renal cell carcinoma and urothelial renal pelvis cancer, account for about 3.3% of all cancers in veterans. Of those, renal cell carcinoma (RCC) represents about 90% of cases. Within the VA, the rate of RCC has held relatively steady, Michael Kelley, MD, VA’s national program director for oncology told U.S. Medicine last year.

In analyses of various subgroups of patients with RCC, the researchers found the general trends of rapid increase followed by leveling off after 2009 applied across most demographic groups. Individuals aged 20 to 44 years were one notable exception, with the incidence rate rising from 1.2 per 100,000 at the start of the study to 3.4 at the end. While two of the three most common contributing factors to RCC increased over the study period—obesity and hypertension—they affected all age groups, leaving the researchers uncertain as to the cause of the uptick in incidence among younger Californians.

Metastatic Disease in Elderly

Mortality rates generally declined, except among Asian and Pacific Islanders, for whom the rate was still lower than that seen in other racial or ethnic groups, and patients over the age of 75. The researchers suggested that some of the increase in mortality among elderly patients could be associated with an increase in metastatic disease seen in this group.

While several new drugs have significantly changed the treatment for RCC in some patient groups (see accompanying article), surgery remains the treatment of choice for most patients. In the California study, 91% of patients with localized RCC had surgery, with the majority having a partial nephrectomy. The average hides a notable trend, however. During the study period, the percentage of RCC patients who had any surgery for the disease dropped from 96.3% to 88.6%.

From 1988 to 2013, the rate of partial nephrectomies for the removal of tumors less than 4 cm increased sixfold, from 13.8% to 74.6%. Surgical resection is the only curative treatment for localized RCC, although about 30% of patients who have surgery will experience a recurrence.

With imaging detecting more, smaller tumors, the challenge of distinguishing which are aggressive and require surgery and which can be managed with watchful waiting has become ever more important. “It’s an important distinction because not all small renal tumors are indolent, and metastatic disease can be present at the time of diagnosis,” said Kenneth W. Kizer, director of the Institute for Population Health Improvement. 

At the VA, the age and health status of many RCC patients further complicates the calculus of the benefit of surgery. “Some renal masses don’t grow very fast, and patients might have comorbidities where they have other illnesses—sometimes very serious ones. The patient in consultation with their physician may decide not to do anything about that mass. Because there’s nothing we can do and there’s nothing we need to do. Other problems will be more pressing,” Kelley said.

Morris and her colleagues acknowledged that surgery may not be the best approach for all cases of RCC, even for patients who can withstand it. “There is some concern that at least a portion of early-detected kidney cancers are actually indolent tumors unlikely to diminish longevity, and that aggressive treatment in these cases may cause more harm than benefit. Furthermore, evaluating outcomes of early-diagnosed cancers can be problematic due to time biases that result in artificially inflated survival estimates,” they wrote.

The authors cautioned against dismissing the importance of even small tumors as previous studies have found that most cases of RCC identified by screening imaging are likely to progress to clinical diagnosis.

  1. Morris CR, Lara PN, Parikh-Patel A, Kizer KW. Kidney Cancer Incidence in California: End of the Trend? Kidney Cancer, 2017; 1 (1): 71

 


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