Doctors Weigh Risks and Benefits of Imaging in Cancer Patients
Allison Gandey
March 10, 2008 (Hollywood, Florida) — National guidelines continue to err on the side of caution when it comes to screening cancer patients. For example, routine computed tomography (CT) scans for lung cancer patients are discouraged, and the evidence does not support the use of posttreatment positron emission tomography (PET) in breast cancer. Experts presenting here at the National Comprehensive Cancer Network (NCCN) 13th Annual Conference debated the pros and cons of imaging in cancer patients.
“There are no absolutes in imaging,” presenter Harmeet Kaur, MD, a radiologist from the University of Texas MD Anderson Cancer Center in Houston, told Medscape Oncology. “In many cases, the CT and PET findings will contradict one another. The only way to deal with these complexities is to take the clinical context into account.”
One of the many concerns with imaging is patient exposure to radiation. How carcinogenic is it and when is screening necessary or worth avoiding? During the question-and-answer period at the end of the session, 1 attendee asked how many scans are considered safe. “I’ve heard that 5 CTs should be considered the limit,” she said. “Is this the case?”
Dr. Kaur said that she has heard of no such number and is unaware of any evidence suggesting this. “We need to screen known malignancies, but the potential risks have to be carefully weighed against the potential benefits, and I think everyone has to find that balance,” she noted.
“The stakes can be high,” presenter Mohammad Jahanzeb, MD, from the University of Tennessee Health Science Center in Memphis, said during an interview. “Without adequate or thorough screening, there are dangers of missing diagnoses. But there are also anxieties associated with nonspecific findings.”
Rely on Radiologists, Experts Urge
During the session, another presenter, David Ettinger, MD, from the Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins in Baltimore, Maryland, encouraged clinicians to rely on radiologists. “They get paid the big bucks and what we’re paying for is their interpretation. I look at all my CTs, but I’m not the one certified to interpret them so I look to the radiologists for their insight.”
Dr. Ettinger said he has noticed a range of capability and has sometimes been frustrated by the noncommittal results provided by younger, less-confident radiologists. He quipped that the results provided by trainees tend to be preliminary results, whereas those offered by faculty tend to be final.
Dr. Kaur said that doctors should give radiologists as much clinical data as possible. “Clinicians won’t get as many noncommittal reports if they provide as much information as they can,” she encouraged.
The presenters said there is a general consensus that any modality should not be interpreted in isolation. PET scans, for example, should be interpreted in conjunction with CT scans. And Dr. Kaur said contrast enhanced CT is preferable.
“To date, one group of people has been interpreting CTs and another group has focused on the newer PET technique. But now that we are combining these 2 modalities, we need a new group of people to specialize in these 2 different tracks.”
Another key imaging controversy pertains to which is better: bone scanning or PET. Dr. Kaur suggested that both are comparable when it comes to sensitivity, but PET has demonstrated better specificity. “PET scanning is generally less widely available, however, so there is still a tendency to rely on bone scans, which aren’t always the most popular with patients,” she said.
During the session, Dr. Jahanzeb outlined the many problems associated with posttreatment PET scanning in breast cancer patients. He pointed out that there is no evidence suggesting that such scanning does any good. “Unfortunately,” he said, “finding metastatic disease early does not increase survival.”
Dr. Jahanzeb added: “It’s like tying a person to train tracks but giving them a pair of binoculars. What’s the point? It won’t do anything to help and you potentially ruin their quality of life in the process.”
The presenters said that the guidelines are not meant to be prescriptive and they acknowledge that there are exceptions. The guidelines are evidence based, but they suggest that roughly 10% of patients fall outside the standard.
Dr. Ettinger pointed out that as clinicians become savvier in treating and curing cancer, patients will be living longer and potentially suffering long-term consequences of treatment. “I think in most cases, the benefits will outweigh the risks. If a patient 20 years from now is suffering the consequences of radiation, I think that patient should be pretty happy. They didn’t die of cancer.”
Dr. Ettinger said that doctors will need to learn from pediatricians who have been dealing with these issues for some time now. “The good news about therapy is that patients are getting better and living longer, but the bad news is that therapy has consequences.”
Dr. Ettinger reports having financial ties to AstraZeneca, Bayer, Bristol-Myers Squibb, Eli Lilly, Genentech GlaxoSmithKline, Merck, MGI, Pharmion, Pfizer, and Sanofi Aventis. Dr. Jahanzeb reports having financial ties to Genentech, GlaxoSmithKline, Merck, Pfizer, and Sanofi Aventis.
National Comprehensive Cancer Network 13th Annual Conference: Controversies in the use of imaging in the management of patients with cancer. Presented March 9, 2008.
