Small lung nodules bring little risk with yearly follow-up

March 4, 2005

As CT screening for lung cancer takes hold, imagers are finding a high incidence of small nodules that must be reported but are most likely benign. Research from Italy suggests that 12-month follow-up is safe in most cases.

As CT screening for lung cancer takes hold, imagers are finding a high incidence of small nodules that must be reported but are most likely benign. Research from Italy suggests that 12-month follow-up is safe in most cases.

Researchers at the European Institute of Oncology in Milan who examined 1035 patients found 238 nodules smaller than 5 mm on standard lung CT screening. Over the course of nearly three years of follow-up, 23.6% of the nodules disappeared entirely, while 66.6% showed no change in size. Only three nodules eventually were classified as malignancies, and all were slow-growing.

Based on those findings, yearly follow-up poses little risk to the patient, said lead researcher Dr. Elvio De Fiori. Statistically, any given small nodule is unlikely to grow so rapidly that the patient's clinical status changes in 12 months.

It's not possible to ignore any small nodules entirely, however. Dr. Stefan Diederich from Dusseldorf, Germany, attempted to characterize small nonprogressing masses in 817 patient followed over five years. Of 998 noncalcified lesions, only 7.7% resolved entirely. While most of those were solid, smaller than 10 mm, and well-defined, no reliable profile emerged of nodules that will resolve over time.

"We can't definitively say you don't need follow-up," he said.

While reducing follow-up to once every 12 months will help minimize radiation exposure, lowering screening dose helps further. At Charite Hospital in Berlin, researchers have experimented with ultralow-dose CT screening that delivers radiation equivalent to a chest x-ray.

They acquired chest screening x-rays of 98 high-risk patients with an average dose of 0.07 to 0.21 mSv, along with a low-dose CT of 0.2 to 0.3 mSv and a standard CT of 4.9 to 12.5 mSv. The low-dose CT found all 52 malignancies identified on regular CT with four false positives. The chest x-ray, by comparison, found only 36, said lead researcher Dr. Uta Zaspel.