Lung cancer is the leading cause of death from cancer in the United States, more than breast, colon, prostate, and pancreatic cancer combined. Smoking is the single biggest cause of lung cancer.
Hi, my name’s David Affleck. I’m a cardiothoracic surgeon at St. Mark’s Hospitalin Salt Lake City. I’ve been asked to talk to you today about screening for lung cancer.
A low-dose CT scan is a CAT scan that’s done with a low dose of radiation and it basically takes thin slices through the chest in order to detect small nodules in the lung that might be early cancers. It’s a very small radiation exposure,about equivalent to what a woman might have with a mammogram. It allows us to get a good picture of the lungs to detect those early cancers. To date, lung cancer screening with low-dose CT scanning, is the only screening tool that we have that’s been shown to reduce, well increase the risk of, increase the detection of lung cancer and thereby decrease the risk of death from lung cancer.
Patients that are appropriate for low-dose CT scanning are those that have an extensive smoking history and they’re divided primarily into two categories. Age 55 to 74 with a 30 pack year smoking history, so they’ve smoked a pack of cigarettes a day for 30 years, and even if they’ve quit smoking in the last 15 years,they still fall in that criteria.
The second criteria is someone that has similar age range but 50 to 74 and they have a 20 pack year smoking history,but they also have a secondary risk factor. Those risk factors can be personal history of cancer, exposure to a heavy metals, silica, those sort of things.
The two categories are extensive smoking history of 30 pack years or 20 pack years plus an additional risk factor. If they’re appropriate to be screened with a low-dose CT scan then they have an annual low-dose CT scan. There’s a lot of discussion about negative CT scans after five years and then stopping that. Usually we find some small nodules that are benign and we follow those for some period of time.
The next step would be a follow-up CT scan at an earlier interval if there’s something suspicious. If it’s a very small nodule, say 5 millimeters, then we might just repeat the scan in one year to make sure that it hasn’t increased in size. The results of the National Lung Screening Trial showed that over 90% of the nodules we find actually turn out to be benign.
So, greater than 90% of the time,even when we find a nodule, those ultimately are benign. Now, if we find something that’s suspicious. For example, it’s a little bit hazy or what we call ground glass appearance our suspicions raised a little bit and we follow those more closely. There is a great deal of evidence that nodules that are between 5 millimeters and 10 millimeters, or half a centimeter to a centimeter, can be followed safely for a period of time provided they don’t have those worrisome characteristics.
Some of the incidental findings, that means things that we weren’t searching for that we find on the CAT scan, are calcification in the heart arteries, or the coronary arteries, occasionally we find a thyroid nodule. We can even see little cysts in the liver, sometimes in the kidneys or the adrenal glands. Again, mostly these are all benign things that we find and so they’re incidental findings. Depending on the finding,then we may refer the patient for follow-up to a specialist in that area. For example, someone that deals with thyroid, we have them meet with that doctor. Most of these findings can be characterized quite easily on CT scan and are known to occur with a certain percentage in the general population.
Low Dose CT Scan Protocol
At St. Mark’s Hospital, we’ve established a low dose CT scan protocol to screen patients at risk for lung cancer. This program has developed over the course of a couple of years, and follows the strict guidelines. The CT scans are ordered by the primary care physician or treating physician, and once ordered,are read by a select panel of radiologists that are trained to read the specific criteria that we’re looking for.
The results of the CT scans are sent back to the primary care physician,as well as to any other doctors that might be involved in the patient’s care. The difference between a chest x-ray and then low dose CT scan isa chest x-ray is a single shot of radiation that has a picture of your chest. Unfortunately, it’s not good at detecting lesions less than one centimeter in size, or 10 millimeters.
A low dose CT scan is taking very thin slices of the lung tissue and allowing us to put those together,stack them, look at the lungs and detect lesions that are less than five millimeters in size. Low dose CT scanning is a much more sensitive test than chest x-ray, and this has been born out of numerous trials in this country, as well as in England. On completion of the low dose CT scan,the referring physician will receive a report from our program within two to three business days.
Patients will receive a letter confirming the CT scan findings and follow up for any future studies. Patients that are appropriate for low dose CT scanning are those that have an extensive smoking history. And they’re divided primarily into two categories. Age 55 to 74, with a 30 pack year smoking history. So they’ve smoked a pack of cigarettes a day for 30 years.
And even if they’ve quit smoking in the last 15 years,they still fall in that criteria. The second criteria is someone that has similar age range, but 50 to 74,and they have a 20 pack year smoking history,but they also have a secondary risk factor.
The risk factors that would qualify a patient in category two for low dose CT scanning to screen for lung cancer include a personal history of cancer in the past, as well as emphysema, pulmonary fibrosis,a family history of lung cancer,and then environmental exposure to elements such as asbestos, arsenic, beryllium,cadmium, chromium, diesel fumes,nickel, silica, uranium, and radon.