Using CT scan of the chest to screen for lung cancer

It is not uncommon to be asked by a patient who has been, or still is, a cigarette smoker whether or not to have a CT scan of the chest.

In the past chest X-rays have been the standard consideration of monitoring a high risk patient for the early detection of a “shadow” that may become a lung mass and a cancer. Early detection of lung cancer offers the best hope for a successful and optimistic outlook.

In the Annals of Internal Medicine (October 18, 2011, Volum 155, Number 8) two articles appeared that address this concern: “Screening for lung cancer: it works, but does it really work?” by Silvesti et al and “Screening for lung cancer: for patients at increased risk for lung cancer, it works” by Jett and Midthun.

So, here are some considerations to ponder in making your decision with your physician.

An important study called the NLST (National Lung Screening Trial) involved 53,454 persons. These were considered heavy smokers and were between 55 and 74 years of age. A comparison between those patients monitored with conventional chest Xray compared to CT scans showed that the latter was more sensitive in finding lung cancer by about 20%.

When patients present with symptoms of lung cancer there is about a 16% five year survival. The goal in helping to improve our patient’s survival is both cessation of cigarette smoking and possibly early detection. If found early, stage I, have a 70% to 80% five year survival. If a person if found to have a later stage IV cancer, the average 5 year survival is only 4%. Clearly, we all want our patients to have an earlier, lower stage lung cancer and whip this disease!

Of the 26, 309 participants who were involved in the CT scan “arm” of the study, 27% had abnormal findings. This must be clearly understood with patients who desire to have these studies performed. The issue is of those 27% findings that were considered abnormal, what happened to those patients? It turns out that 96% were “false positives”. This means that most of these abnormalities found were not cancer.

Many have further radiation exposures with further testing, repeat CT scans, PET scans, Chest Xrays, etc. Others end up have needle biopsies of these abnormalities done and still others proceed to surgery. Many of these tests or procedures are ultimately found out to have been unnecessary. The risks for lung cancer due to a low dose CT scan of the chest is estimated at about 1-3 deaths per 10,000 screening tests performed.

Patients that have needle biopsies done have about a 1% chance of bleeding. Of those, 18% end up with blood transfusions. A collapse of the lung, called a pneumothorax, is seen about 15% of the time. Of those patients, 6% end up with a chest tube and hospitalization.

If the screening low dose CT scan study was without abnormalities the next question is what to do with those patients? The final census is not known yet, but in patients who are significant smokers (eg. 30-pack years or more) they should be at least considered to have repeat low dose CT scans yearly for three years, per this review.

If on the other hand, an abnormality is found on the first screening study, a careful review with your doctor and/or lung specialist will decide what course is best suited for you.

Remember that at the time of this writing, Medicare and insurance companies do not routinely reimburse for the low dose screening CT scan of the chest. This is another variable that must be taken into account.

On other point, the CT scanner itself and the person who interprets the scan all come into play as to the quality of the study and its proper evaluation. Please discuss this with your doctor as well.