Recent advances in computed tomography scanning soon could rob lung cancer, the second-leading cause of death in the U.S., of much of its lethal punch.
Researchers at New York Hospital Cornell Medical Center and New York University Medical Center have found that fast CT scans taken months or even weeks apart can reliably identify lung tumors at an early stage when treatment is highly effective.
They hope that the imaging techniques, which take as little as 90 seconds on high-performance CT machines, could be used to screen patients at high risk for lung cancer, much as mammography is now used to detect early-stage breast cancer.
"We're finding that CT scanning . . . is doing better than we even thought," said Claudia Henschke, M.D., a radiologist who presented the data at the Radiological Society of North America's 84th annual scientific meeting in Chicago last week. "Lung-cancer screening is feasible."
The CT scanning technique used by Henschke's group costs $150 to $200 per scan and requires no injections of contrast agent or special patient preparation to perform. The research subjects were 60 years old or older and had smoked the equivalent of a pack a day of cigarettes for at least 10 years.
Henschke's group detected 228 suspicious lung nodules in 1,000 patients scanned by CT during a four-year period. Among those patients, 22 turned out to have malignant tumors at biopsy. The same patients also had chest X-rays, the more common first-line diagnostic technique used for unspecified lung problems. However, only five of the cancerous tumors were also found on chest films.
Currently, screening for lung cancer is not recommended. Previous studies using chest X-rays to screen for the disease showed no clinical benefit, Henschke said.
However, early lung-cancer detection by CT could produce significant clinical rewards. Among the 22 patients with lung cancer, 17 had the disease in the earliest of six standardized stages. "We know these are real lung cancers that would cause death," she said. But as a result of the early warning, these patients, Henschke said, have a 70% to 90% chance of living at least five years.
A critical CT imaging advance by Henschke's group made the new screening protocol possible.
The scientists developed precise methods for quickly and accurately calculating the growth rate of tumors by comparing its volume in sequential CT exams.
Fast-growing tumors are much more likely to be malignant than stagnant or slow-growing masses. Careful calculation of tumor growth rates can minimize cancer false alarms by reserving painful and expensive biopsies for only the fast-growing tumors most likely to be malignant.
Significantly, Henschke said only one biopsy turned up a benign tumor, confirming that the CT protocol was specific as well as sensitive. This was an important factor in winning over referring physicians and patients, she said.
If the baseline findings of Henschke's group are borne out by one-year follow-up CT exams, as she says is likely, the study could lay the groundwork for policymakers to consider annual CT lung-cancer screening for the millions of people at risk for the disease.
Whether it's appropriate to consider screening for lung cancer in the near future is "very much an open question," said Robert Smith, senior director for cancer detection and treatment at the American Cancer Society headquarters in Atlanta. This week lung- cancer experts, including Henschke and Smith, are convening in Italy to discuss the matter.
Though probably years away even under the most optimistic scenario, widespread CT screening for lung cancer would swell demand for scans in hospital and outpatient imaging centers and strain the budgets of insurers asked to pay for the exams.
The stakes are huge both in terms of human lives devastated by the disease and the financial commitment a massive screening campaign would require.
The American Cancer Society expects more than 171,000 new lung cancer cases will be diagnosed in 1998. Because most of these cancers aren't found until they have grown large enough to cause symptoms, lung cancer usually defeats attempts at treatment. Despite steady advances in surgical techniques, chemotherapy and radiation therapy, only 14% of all lung-cancer patients are still alive five years after diagnosis, according to the cancer society. This year alone, more than 160,000 people are expected to succumb to the disease.
"It's like having two jumbo jets crashing every single day of the year," Henschke said.
But if the disease is detected early, survival rates improve dramatically.
However, instituting widespread screening for lung cancer would be a momentous public health decision.
Millions of outwardly healthy people would be exposed to radiation, albeit modest doses, and society would bear a tremendous direct cost to pay for the program. If even two million people were screened this way each year, the total cost of the CT images alone would be at least $300 million.
For both fiscal and ethical reasons, scientists and policymakers must satisfy meet a heavy burden of clinical proof to recommend screening.
While encouraged by the CT screening results, other scientists urged caution.
"Clearly, we'll be able to find smaller nodules than chest films," said Carl Ravin, M.D., chairman of radiology at Duke University School of Medicine. But he stressed the need for longer-term follow-up to make sure the information was as clinically useful.
"Will patients in the CT (group) survive longer?" he asked.