CT Colonography Detects Cancers Inside and Outside the Colon

Fran Lowry

April 01, 2010

April 1, 2010 — More than 1 in every 200 asymptomatic people undergoing routine screening with computed tomographic colonography (CTC), or "virtual colonoscopy," were found to have a clinically unsuspected malignancy, most of which were located outside the colon.

Because the majority of these cancers were found at an early stage, clinical outcomes to date have been very favorable, researchers report in the April issue of Radiology.

The finding is a clear sign of the utility of CTC and proponents of the noninvasive test hope that it will help persuade the Centers for Medicare and Medicaid Services (CMS) to finally allow the test to be covered by Medicare as another option for colon cancer screening in American seniors.

The CMS decided that CTC would not be covered by Medicare in May 2009, as reported by Medscape Oncology, concluding that there was insufficient evidence that the test improved health benefits for asymptomatic average-risk Medicare beneficiaries.

"Now they have proof," Andrew Spiegel, CEO of the Colon Cancer Alliance, a national patient advocacy organization, told Medscape Oncology. "This study shows that there is indeed evidence that the test is beneficial and relevant to the Medicare-age population."

A Surprising Finding

"We were surprised by our findings," lead author Perry J. Pickhardt, MD, professor of radiology and chief of gastrointestinal imaging at the University of Wisconsin Medical School in Madison, admitted to Medscape Oncology. "We weren't expecting to find this number of important findings outside of the colon. CTC is unique among colorectal cancer screening tests in its ability to evaluate extracolonic structures."

Dr. Pickhardt and his team analyzed the stage, treatment, and clinical outcomes of all unsuspected cancers that were detected at routine screening CTC in 10,286 adults (5,388 men, 4,898 women; mean age, 59.8 years) from a retrospective review of their medical records.

All screenings were performed from April 2004 to March 2008.

They found unsuspected pathologically confirmed cancers in 58 (0.56%) subjects — colorectal cancer in 22 (0.21%) and extracolonic cancer in 36 (0.35%) patients.

The mean age of the patients with unsuspected cancer was 60.8 years, which is, on average, 1 year older than the mean age of those without cancer (59.8 years; P = .32).

Extracolonic cancers were renal cell carcinoma in 11 patients, lung cancer in 8 patients, non-Hodgkin's lymphoma in 6 patients, and a variety of other cancers in 11 patients.

Most (53.4%) of the cancers were stage I or localized at diagnosis. Six patients had stage II disease, 12 had stage III disease, and 7 had stage IV disease. Two patients with carcinoid tumors had regional lymph node involvement.

Forty-six patients (79.3%) underwent surgical (n = 43) or endoscopic (n = 3) resection, and 2 patients with renal cell carcinoma underwent percutaneous ablation.

Nineteen patients (32.8%) received chemotherapy or hormonal therapy and 7 patients (12.1%) received radiation therapy.

The mean follow-up was 30.2 months (range, 12 to 56 months), and the follow-up interval was at least 1 year for all patients. At the time of the most recent follow-up, 54 of the 58 patients (93.1%) were alive, and the majority were in good health with no evidence of disease, Dr. Pickhardt said.

"To our knowledge, there has been no disease progression in patients with stage I, stage II, or localized disease at diagnosis," he said.

Three patients died from their cancer: 1 from metastatic colorectal cancer, 1 from metastatic bronchogenic carcinoma, and 1 from malignant mesothelioma. All of these cancers were advanced at the time of diagnosis. The other death was from an unrelated cause.

CT Colonography a Double-Edged Sword

"It appears that CTC can provide a more comprehensive evaluation than simply [colorectal cancer] screening all in one single test," Dr. Pickhardt said in an interview. "In addition to finding extracolonic cancers, CTC can detect abdominal aortic aneurysms and even screen for osteoporosis and other often silent conditions."

But this ability also means that CTC represents a double-edged sword, he added.

On the one hand, CTC can reassure the great majority of patients that important disease is absent. On the other, CTC will reveal something that looks suspicious in about 6% of cases. This results in the need for additional imaging. Half of the time, the suspicious finding turns out to be clinically relevant.

"Potential harms include the anxiety, inconvenience, potential complications, and added costs related to additional diagnostic workups for findings that ultimately prove to be unimportant," he explained.

But the benefits include the potential for early diagnosis of cancer at a time when the possibility of cure is greatest.

CTC also has been shown to be more clinically and cost effective than colorectal cancer screening in detecting aortic aneurisms and extracolonic cancers, Dr. Pickhardt said.

Commenting on the cost-benefit issue, Beth G. McFarland, MD, a radiologist from the Center of Diagnostic Imaging in St. Louis, Missouri, and recent chair of the American College of Radiology colon cancer committee, said that the issue of extracolonic findings at CTC has been controversial.

"Since CT colonography scans the entire abdominal and pelvic cavity from the lung bases to the pelvis, much more anatomic detail of organs beyond the colon are evaluated. To some third-party payers — especially CMS — this has raised red flags about concerns of the potential extra costs of additional imaging tests needed to further evaluate these extracolonic findings," she said. "The bias has been that these are unfavorable additional costs; however, this study introduces the other side, namely that there can be cost savings. Early detection and treatment of unsuspected cancer can prevent progression of disease, which can have a tremendous cost savings. Although this effort does not prove that cost savings outweigh cost expenditures, it certainly shows that better efforts to model downstream cost savings from early cancer detection need to be developed."

If CTC Is Good Enough for President Obama . . .

According to Mr. Spiegel, the CMS is running out of excuses for not covering CTC, especially now that this study has been published. The Colon Cancer Alliance is seeking to introduce new legislation to have Congress mandate that the CMS cover CTC screening.

"We recently met with them and it was a more positive meeting than in the past. President Obama had his first colon cancer screening test [in March] and he chose virtual colonoscopy. So if he and his medical advisors feel that this test is good enough for him, it ought to be good enough for American seniors."

Dr. Pickhardt also hopes that the CMS will sit up and take notice of his study's findings. "One of the CMS's main concerns is the uncertain consequences of extracolonic evaluation. In the end, I believe that the extracolonic evaluation at CTC provides a net benefit to patients."

Dr. Pickhardt reports financial relationships with Viatronix and Medicsight. Mr. Spiegel and Dr. McFarland have disclosed no relevant financial relationships.

Radiology. 2010;255:83-88. Abstract

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