Pearls of Wisdom: Radiation Exposure During Lung Cancer Screening

Arnold is a 62-year-old man with a 80 pack-year smoking history who will soon be undergoing standard low-dose spiral computed tomography (LDCT) screening for lung cancer.

He mentions that he is nervous about the procedure and asks how much radiation is used in an LDCT.

You explain to him that the dose of radiation delivered through LDCT would be best compared to:

A. A day in bright sunlight at the beach
B. 15-20 chest radiographs
C. 30-40 chest radiographs
D. 110-120 chest radiographs 

What is the correct answer?
(Answer and discussion on next page)

Louis Kuritzky, MD, has been involved in medical education since the 1970s. Drawing upon years of clinical experience, he has crafted each year for almost 3 decades a collection of items that are often underappreciated by clinicians, yet important for patients. These “Pearls of Wisdom” often highlight studies that may not have gotten traction within the clinical community and/or may have been overlooked since their time of publishing, but warrant a second look.

Now, for the first time, Dr Kuritzky is sharing with the Consultant360 audience. Sign up today to receive new advice each week.

Answer: 110-120 Chest Radiographs    

While the amount of radiation incurred through screening might seem the least of our patients' worries, I believe we still owe it to them to help clarify and quantify, whenever possible, any risks, toxicity, or potentially consequential burden of investigations that involved exposure to x-ray radiation.

“Typical” Effective Doses of X-rays

A standard CT scan of the chest delivers a radiation dose of 8 to 10 millisieverts (mSv), which is the equivalent of 600 to 750 chest radiographs. Low-dose CT, at 1.5 mSv, certainly features a dramatic reduction in the radiation dose, but it still represents the equivalent of approximately 113 chest radiographs. Considering that LDCT is recommended in at-risk individuals every year through age 80, this is quite a lot of radiation. Additionally, positive findings detected on LDCT may require follow-up imaging, in which case diagnostic CT is utilized at the level of 10 mSv.

The table below outlines the estimated number of radiation-related cancers that might be anticipated from repeated screening with LDCT.

Estimated Radiation-Related Cancers from Repeated LDCT Screening

What’s the “Take Home”?

The dose of radiation involved in LDCT screening is not insubstantial, and clinicians may want to provide patients with a full disclosure of the radiation burden before embarking on this screening process.

Reference:

Linet MS, Slovis TL, Miller DL, et al. Cancer risks associated with external radiation from diagnostic imaging procedures. CA Cancer J Clin. 2012;62(2):75-100.