Lung Cancer Screening With CT?
Early detection: Computed tomography (CT) examinations could reduce the number of lung cancer deaths, at least among smokers. But at the same time, the images very often trigger false alarms
Dangerous growth? CT image with abnormal findings (left)
© Your Photo Today / PHANIE Voisin
To date, women and men in Germany are entitled to a total of five examinations for the early detection of cancer. A sixth could be added in the next few years. Objective: the diagnosis of lung cancer in a stage that is as curable as possible. The procedure for introducing the investigation is already ongoing.
On the trail of suspicious herds
It is already clear that when the offer comes, health insurances will only reimburse heavy smokers for the costs. Because 85 to 90 percent of lung tumors are due to tobacco. And only in this group of patients can the benefits offset the disadvantages of the examination.
Specifically, it is about imaging the lungs using computed tomography (CT). All that is needed is a low dose of radiation. It corresponds roughly to the average annual natural background radiation in Germany, and it will continue to decrease with new devices. As doctors say, suspicious foci can be identified better with the images than with X-rays. However, the finding is by no means always clear.
Early detection for smokers
Nevertheless, the expert commission for early detection in the USA, which is known to be critical, recommends such an examination - but only to smokers who have more than 30 so-called pack years behind them. That corresponds to one pack of cigarettes a day for 30 years or two packs a day for 15 years.
Such frequent smokers, according to the expert opinion, should make use of the early diagnosis annually between the ages of 55 and 80 - unless they have been abstinent for more than 15 years.
The recommendation is based on an examination of more than 53,000 people in whom researchers had examined the chances and risks of the CT examination. The conclusion of the study: the risk of dying from lung cancer can be reduced by 20 percent. In absolute numbers: of 100,000 smokers who were examined three times by CT instead of an X-ray, 62 fewer died of lung cancer each year.
Women are more likely to benefit than men
European experts did not want to rely on the US data and published their own studies. Most of them are arguably too small to provide statistically accurate evidence of a decrease in lung cancer deaths.
"If you summarize the studies in a so-called meta-analysis, you can clearly see this effect," explains Professor Rudolf Kaaks, head of the cancer epidemiology department at the German Cancer Research Center in Heidelberg. He was involved in the evaluation of a corresponding German study.
One result of the research work: women benefit more from early detection than men. Why is not entirely clear. They may be more likely to develop a type of lung cancer that can be seen particularly well on CT.
Too many false positives
But for women as well as men, the investigation has a downside: the so-called false-positive findings - recordings classified as suspicious, which later turn out to be a false alarm. Their rate was 95 percent in the US study. Only in one out of 20 cases did the CT provide the correct information.
Professor Hans-Ulrich Kauczor heads a commission of the German Radiological Society on lung cancer screening
© W & B / Andreas Reeg
In a recent, large European study on the subject, 60 percent of the findings were still false-positive. Most of the patients who were called to see a doctor for this reason had to go through the CT tube again. In others, the airways and lungs were examined endoscopically, a biopsy was taken, or the suspicious focus was removed immediately. The complication rate for such interventions was less than one percent, and deaths were extremely rare. But the patients had to endure the greatest fears unnecessarily.
The point system should decide on the right to early detection
"We absolutely have to reduce this damage caused by the examination", demands Professor Hans-Ulrich Kauczor, who heads a commission of the German Radiological Society for lung cancer screening. The best way to achieve this is through a stricter selection of participants.
In addition to the age and duration of the smoking history, further criteria should be taken into account, says Kauczor. This includes the type of cigarette, the age when you started smoking, previous illnesses, the family risk, how often the patient had pneumonia. All these factors should be included in a point system that decides whether there is a right to the early diagnosis examination.
In addition, the definition of a suspicious finding could be narrowed down. In the US study, the limit was a hearth of at least 0.4 millimeters. Most of the lumps in this area are benign, or the cancer has not yet invaded the surrounding tissue. Hence, Kauczor would raise the threshold.
Experts are looking for other methods
Re-admission months later could clarify whether the hearth is growing at all and how quickly. For many of those examined, however, such a waiting time would be difficult to bear.
Whether a stricter selection of participants or a more liberal assessment of the findings: Both ways could reduce the rate of false alarms. At the same time, however, they have the disadvantage that some of the patients would recognize the danger later.
The relationship between the benefits and risks of a Germany-wide program is now initially being clarified by the Federal Office for Radiation Protection (BfS) together with a specialist commission. "As a first step, our experts examined which other early detection programs are possible and classified lung cancer screening as a priority," says a spokeswoman for the agency.
320 long-time smokers must be screened to prevent lung cancer death
© W & B / Jörg Neisel
Decision on assumption of costs
The working group has just started to evaluate the scientific literature. It then determines which requirements the devices should meet and how the medical staff should be trained. The Federal Environment Ministry uses the evaluation of the BfS as a guide when it ultimately has to decide whether it will allow the early detection examination for lung cancer despite radiation exposure.
If the ministry says yes, the introduction of a national program on health insurance costs is by no means guaranteed. Experts suspect that there will be model tests first.
Finally, the Federal Joint Committee of Doctors, Health Insurance Funds and Clinics has to decide whether and for whom the insurance companies have to bear the costs. And what requirements the institutions that are allowed to carry out the investigation have to meet. "There are still a few questions to be clarified, that will certainly take a few more years," said Rudolf Kaaks.
Quitting smoking is most effective
Carefully estimated, such an early detection program could prevent every fourth to fifth lung cancer death within ten years. Currently, lung cancer is often discovered very late. Most people die within a few months to two years of diagnosis.
For smokers who want to avoid this fate, however, there is a much more effective measure than a CT scan: stop.