In December the United States Preventative Task Force completed its review of the available science on whether using a low dose CT scan could reduce the number of lung cancer deaths. Lung cancer is the most lethal cancer, likely due to its late detection. Treatment in late stage lung cancer is seldom successful, and is invasive (i.e., surgery, radiation, chemotherapy).
The task force members reviewed 6 effectiveness studies and 20 studies that explored adverse effects from low dose CT - including exposure to radiation, the rate of false positives and the associated stress and unnecessary procedures that follow false positives. You can read the summary and full report from the task force here.
It appears that only one of the studies that found a protective effect from low dose CT was of high quality. That study showed reduced lung cancer death as well as reduced death from any cause (all cause mortality) in the smokers who received the CT. The evidence from this study and several moderate quality studies was convincing enough to some to recommend the screening change.
I am addressing the issue in my blog for two reasons, 1) I have worked in the smoking cessation field and 2) I often post about medical radiation and my grave concern over excessive use of imaging. Almost four years ago, I wrote this post which was an over view of chapter 4 in the President's Cancer Panel report on Reducing Environmental Cancer Risk. Chapter 4 is Exposure to Hazards from Medical Sources. From that chapter we learned that CT scans are over used, that they expose the patient to high levels of radiation (higher levels than are necessary for the scans to be effective) and that the radiation dose from a CT scan can increase a person's risk for cancer.
The new recommendations are for physicians to offer the low dose CT (LDCT) to persons who are between the ages of 55 and 74 who have smoked 1 pack of cigarettes per day for 30 years or 2 packs per day for 15 years, or any other combination that would equal 30 pack years. If a person has this smoking history, but has quit smoking, they should still have the screens if they have been smoke free for less than 15 years. [Notice the significant screening criteria - SMOKERS only. To me this is as strong a declaration on the lethal consequences of smoking as one will ever hear.]
According to the task force, 20% more lung cancer deaths could be prevented if these heavy smokers were screened with LDCT instead of a chest x-ray. I do not know what this means in actual numbers, i.e., 20% of how many - how many do X rays find?
What I did spend time looking for was the amount of radiation a low dose CT provided. Recall from chapter 4, not all imaging machines deliver the same amount per test .. so a rough estimate is the best we can do. The estimate is that low dose CT delivers the radiation equivalent of about 15 xrays. Fifteen! Radiation in this case is measured as millisieverts, or mSv. A regular chest CT has 5 to 20 mSv and the low dose CT has 1 to 4 mSv. Better - still a heck of a lot and more than I would routinely expose myself to. (To be fair, some estimates of the radiation in regular chest CT suggest the equivalence of 350 Xrays... yes that is three hundred - so to answer my question; indeed, the low dose CT is a lower dose of radiation)
In the summary from the report, it is clearly stated that most lung cancer is caused by smoking and that the most important thing we can do to reduce death and disease from lung cancer is to reduce smoking.
I am really concerned that smokers will keep smoking because they believe that this screening will find a tumor in time to remove it. That is a HUGE risk. Click here to learn more about quitting.. I did it, so can you.