Recent studies have highlighted the quandary of incidental findings on CT scans for radiotherapy planning. In the last eight years, studies have found that incidental findings occur in rates varying from 11% to approximately 30% on CT planning scans -- with a minority of these findings clinically significant. What is the radiation oncologist's course of action in cases involving incidental findings, and is there a standard of care that should be followed?
To find out, AuntMinnie.com reviewed some of the published literature on incidental findings and polled radiation oncologists about the practical and legal ramifications of incidental findings on CT scans for radiotherapy planning.
"I don't know of any medical center that has a written policy about incidental findings, but from both a legal and moral point of view, the radiation oncologist has a clear duty to report incidental findings," said Dr. Leonard Berlin, chairman of the department of radiology at Rush North Shore Medical Center in Skokie, IL.
Reporting incidental findings to the attending physician makes good sense legally, because if incidental findings are not reported and a patient goes on to develop a secondary cancer a year down the road, the radiation oncologist could be legally culpable, added Berlin, who is also a professor of radiology at Rush Medical College in Chicago.
However, should a diagnostic radiologist also be called in to consult on every incidental finding? Most radiation oncologists that AuntMinnie.com talked with argued that calling in a diagnostic radiologist for an incidental finding should be a standard of care. But studies have found that rates of incidental findings are low, and the percentage is even lower, in the range of 1% to 9%, for those that actually turn out to show additional benign conditions or cancerous growths that require further treatment.
Facts and figures
Here's a look at the literature and recent studies about incidental findings.
In a 2001 paper, Drs. Vivek Mehta and Don Goffinet reviewed 153 sequential scans of breast cancer patients referred for breast or chest wall radiation therapy at Stanford University Medical Center in Stanford, CA.
The planning scans were extended to cover the breast, neck, thorax, and liver. Any abnormal findings were additionally reviewed by a diagnostic radiologist. The researchers noted 17 (11%) previously unsuspected abnormalities, involving the lung, liver, gallbladder, esophagus, lymph nodes, and breast. In the end, four of these abnormalities represented additional cancer foci (about 3%) that required a change in treatment plan (International Journal of Radiation Oncology, Biology, Physics, March 1, 2001, Vol. 49:3, pp. 723-725).
In another study, Mehta -- this time with co-author Dr. Melanie Smitt -- prospectively evaluated the treatment planning scans of 162 radiotherapy patients. They also reviewed the diagnostic reports and records on all the patients to determine the incidence of previously unknown benign or cancer-related findings, the impact of such findings on treatment, and the need for additional radiologic studies or procedures based on the CT interpretations.
According to the results of that research, 32 (20%) of the patients had incidental benign findings. Of these, the researchers noted that three were clinically important: two aneurysms and one possible deep vein thrombosis.
Additionally, in 20 patients, the physicians found possible cancer-related findings involving the liver, lymph nodes, abnormal soft tissue, small bowel, and breast. After reviewing prior diagnostic studies and obtaining additional imaging, the physicians concluded that only three of the previously unknown findings required further investigation: two aneurysms, which did not require near-term treatment, and one metastatic neck node.
"Routine diagnostic interpretation of radiotherapy planning scans resulted in few important medical findings and changed patient care for less than 1% of patients," Mehta and Smitt wrote (American Journal of Roentgenology, September 2001, Vol. 177:3, pp. 521-524).
More recently, Dr. Anushka Patel and colleagues from the Henry Ford Health System in Detroit found that 15% of 351 early breast cancer patients treated over six years showed incidental findings on their CT planning scans for radiotherapy.
The scans were reviewed by a diagnostic radiologist, who determined that 60% of the incidental findings were potentially significant -- possibly signaling metastatic disease -- and worthy of additional imaging with MRI and CT. Among the 31 patients who required additional workup, 9% had clinically relevant findings. Patel presented the group's findings at the 2007 American Society for Therapeutic Radiology and Oncology (ASTRO) meeting in Los Angeles.
One reason for the low rate of incidental findings is that patients often get extensive staging and workup for metastatic disease before they undergo radiotherapy planning CT scans. Patel said that her group did not find any correlation between staging distribution and abnormal incidental findings. However, they did note that older patients (mean age of 65.9 years) were more likely to have incidental findings versus those without such findings (mean age of 58.5 years).
While the group also found that more smokers had lesions categorized as previously unrecognized (or incidental findings) compared to nonsmokers, this particular result did not reach statistical significance, according to Patel.
"I was very surprised by that -- one would think that, of any group, smokers would tend to have more incidental findings, but it just wasn't the case," Patel said. The reason may be that today's careful imaging and follow-up may find metastatic disease -- even in smokers -- before the patient undergoes the CT planning scan, she added.
Patel noted that a review of all CT planning scans by a radiation oncologist for incidental findings is now a standard of care at her medical center. She also stated that it was important for radiation oncologists to look at other sites beyond the organ slated for radiotherapy. Any incidental finding should prompt a review of the patient's medical history and any comorbidities. And if the abnormality is significant, a diagnostic radiologist should be consulted.
Expert advice
In general, reporting incidental findings is considered part and parcel of the standard of care at many major cancer centers, but specific institutional policies dictating how these findings should be handled are not necessarily in place.
Dr. Thomas Buchholz, chair and professor in the department of radiology at University of Texas M. D. Anderson Cancer Center in Houston, told AuntMinnie.com that the center does not have an official policy about reviewing incidental findings. But to fulfill today's standard of care, any abnormal finding should be reviewed by a diagnostic radiologist, he said.
The problem is that many CT treatment planning scans are taken under different conditions than diagnostic scans and are of poorer quality. CT planning scans are often taken without contrast and breath-holds, for instance. However, even though these CT scans are not of the highest quality, they can still yield clinically important information, Buchholz said.
"It can provide us with good information that can affect treatment planning, as well as the clinical care of the patient," he explained. "Of course, it can also point us toward a red herring -- and, in those cases, may cause a patient some distress."
On the whole, Buchholz said, it is crucial to have incidental findings made known to the patient and have the findings reviewed by a diagnostic radiologist, even if it does cause some anxiety for patients. "Most patients would want to know of any unusual incidental finding," he said.
But should every single incidental finding require the scrutiny of a diagnostic radiologist? Making that decision can be a "hard call," according to Dr. Steven Feigenberg, an associate professor of radiation oncology at Fox Chase Cancer Center in Philadelphia.
"There isn't always a simple answer, especially since the quality of these scans is not as good as diagnostic scans. Undoubtedly, there are cases where we miss unexpected findings, because we're just not looking for them," he said. In his experience, only a handful of incidental findings have been additional cancers. These additional cancers may or may not need treatment right away, Feigenberg noted.
Yet any concern about subjecting the patient to additional scans is probably outweighed by the necessity of following up on unusual findings. "If I think something doesn't quite look right, then I'm going to take it to a diagnostic radiologist," he said.
In smaller hospital centers, radiation oncologists may be less likely to send incidental findings to a diagnostic radiologist, simply because of the cost involved, noted Dr. Ken Murdock, a locum tenens radiation oncologist and PET/CT specialist. He estimated that 5% to 7% of the time, he finds incidental findings that signal a metastasis. On top of that, he estimated that 15% of the time the findings are merely a marker of inflammation, which may not be clinically significant. "I find incidental findings more often in poorly differentiated tumors," he said.
Murdock stated that he does consider sending anything questionable to a diagnostic radiologist as part of his job. "There are some occasions where a radiation oncologist might pass off an incidental finding and say it's nothing to be excited about, but I usually advocate for getting an opinion from a diagnostic radiologist," he said.
Murdock holds nine state licenses, and believes strongly in following up incidental findings even in the smaller hospital centers where he works.
"It's important to the quality of care," Murdock said. "Not only is it important for standard of care, but it's important for patients. If we get an incidental finding of a colon cancer on a CT planning scan and refer that patient for treatment, it's going to save him or her a lot of trouble down the road."
By Barbara Boughton
AuntMinnie.com contributing writer
March 13, 2008
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