Radiation

In the past few years, there have been a number of articles in the medical as well as the lay media suggesting that CT scans can cause substantial harm and may cause cancer.

Harm can come in the form of improperly done CT scans that inappropriately expose patients to much higher than necessary levels of radiation exposure - another reason why CT screening should only be done at a competent, experienced site that adheres to a well-defined protocol for screening.

The evidence suggests that the risk of cancer caused by lung cancer screening CT-scans is very low.

Furthermore, it is well understood that radiation risk of future cancer is much higher when children and young adults are exposed to radiation than when older people are. One reason for this is that cancers caused by radiation exposure occur many years after the exposure. Young people are not and will not be screened for lung cancer. Only older adults, who are known to have a markedly lower lifetime risk of subsequent cancer from radiation exposure, would receive screening CT scans in properly conducted lung cancer screening programs.

In addition, there is substantial data from multiple sources that demonstrates no measurable increase in cancer incidence or mortality resulting from diagnostic radiographic studies in adults.

Radiation exposure received by adult women during radiation therapy for breast cancer results in much higher radiation exposure than does radiation exposure from lung cancer screening, by an enormous factor. And yet, even in the case long-term follow-up following such high-dose radiation therapy treatment for breast cancer, in tens of thousands of non-smoking adult women, there is no indication of any statistically increased incidence of lung cancer on the side of radiation therapy compared to the contralateral un-radiated lung.

CT scans are not new. Diagnostic CT scans were first performed in the U.S. at the Mayo Clinic in Rochester, MN in the early 1970s and there has been a steadily increasing use of the technology during the subsequent 40 years. At present, the number of CT scans performed exceeds 70,000,000 each year.

CT scans make up only a percentage of total radiation exposure from diagnostic procedures such as x-rays and angiograms. Yet, when looking for an increase in total cancers in the U.S. that might have been caused by these diagnostic tests, one finds that there is no identifiable increase in the incidence of cancer in the U.S., despite the marked increase in the number of CT and angiographic studies performed over the past 40 years. Rather, the overall incidence of cancer in the U.S. is decreasing, as is the number of cancer deaths.

Furthermore, if one looks at annual incidence in the U.S. of cancers known to occur in children exposed to high-dose radiation therapy, such as leukemia and soft tissue sarcoma, again, there is no evidence of increased numbers of these cancers.

The bottom line is that, despite speculation to the contrary, if there is any increased risk of cancer caused by low-dose CT scans in middle-aged and elderly individuals at high risk of lung cancer because of previous or current smoking, it is not measurable, and must be very small. There would accordingly be a highly favorable risk to benefit ratio in the chance of the individual suffering and dying of lung cancer as a result of lung cancer screening.

Finally, even if a hypothetical cancer occurred within the field of a previous chest CT scan, one might reasonably expect that such a radiation-induced cancer would be diagnosed by subsequent computerized tomogram studies in early, curable stage.