Sub-mSv CT bests chest x-ray for lung cancer follow-up

Low-dose chest CT delivered much greater sensitivity at lung cancer detection than chest x-ray, according to a study presented May 6 at the American Association for Thoracic Surgery meeting. Radiation exposure for the sub-mSv CT protocol was on par with chest x-ray.

Chest x-ray has served as the standard of care to monitor patients after lung cancer surgery. However, physicians had been reluctant to utilize CT imaging, primarily because of concerns about radiation exposure, according to Waël C. Hanna, MDCM, MBA, of the department of thoracic surgery at University of Toronto.

Minimal dose CT (MnDCT) of the thorax, which delivers radiation exposure of 0.2 mSv, offers a new model that keeps exposure on the 0.16 mSv range of chest x-ray.

Hanna and colleagues hypothesized that surveillance of patients with completely resected lung cancer via MnDCT, compared with chest x-ray, could deliver earlier detection of recurrence and higher rate of treatment of new or recurrent disease.

Between 2007 and 2012, the researchers prospectively enrolled 311 patients after curative resection of lung cancer. Patients underwent MnDCT and chest x-ray at three, six, 12, 18, 24, 36, 48 and 60 months after surgery. A total of 1,096 pairs of chest x-ray and MnDCT images were analyzed by radiologists blinded to the other modality.

If a radiologist suspected new or recurrent disease, full-dose CT and/or biopsy was ordered to confirm the diagnosis.

MnDCT delivered sensitivity of 94 percent, compared with 21 percent for chest x-ray. MnDCT edged out x-ray in terms of negative predictive value for the diagnosis of new or recurrent lung cancer at 99 percent and 96 percent, respectively.

Of the 63 patients diagnosed with new or recurrent disease, 46 cases were asymptomatic and detected only via MnDCT. Seventy-six percent of these asymptomatic patients were treated with curative surgery or radiation; median survival was 69 months from the first surgery. The remaining patients received palliative care and survived a median 25 months.

“MnDCT offers the best of both worlds: on the one hand it allows for precise imaging close to what is produced from a standard CT scan, and on the other hand it only delivers a small amount of radiation which is comparable to what a regular x-ray would deliver and much less than a standard dose CT scan,” Hanna said in a release. “More importantly, now we can detect recurrent lung cancer at a much earlier stage, allowing patients to possibly undergo another surgery, and live longer, healthier lives."