William Henry Moore MD, Presenter: Research Grant, EDDA Technology, Inc Medical Board, EDDA Technology, Inc Research Grant, Galil Medical Ltd Research Grant, Endo Health Solutions Inc

Ammar Ahmed Chaudhry MD, Abstract Co-Author: Nothing to Disclose

Yair Chaya MD, Abstract Co-Author: Nothing to Disclose

Thomas Bilfinger MD, Abstract Co-Author: Nothing to Disclose

Samantha D. Glass MD, Abstract Co-Author: Nothing to Disclose

Sarel Gaur MD, Abstract Co-Author: Nothing to Disclose

George Mikhail MD, Abstract Co-Author: Nothing to Disclose

Kevin S. Baker MD, Abstract Co-Author: Nothing to Disclose

Bong S. Kim MD, Abstract Co-Author: Nothing to Disclose

To evaluate whether the pattern of nodule enhancement on delayed contrast-enhanced CT performed after Stereotactic ablative Radiotherapy (SABR) for early-stage lung cancer can differentiate individuals with recurrence from non-recurrence.

A retrospective study was performed evaluating a total of 81 patients who underwent SABR for primary stage I or II lung cancer with follow-up contrast chest CT at 1, 3, 6, 12, 18, and 24 months. The size of the ablation zone was measure in addition CT density of the nodules were obtained pre-contrast and at 30 seconds and 1, 2, 3, and 4 minutes post contrast injection at each follow-up. Each ablation zone was measured five times using a uniform region of interest pre-contrast and at each time point after contrast. The mean attenuation of these five points was recorded. The CT bed position was used to ensure that the same area was interrogated with each subsequent time point.

60 patients were included in this study. 49 patient without evidence of recurrence and 11 patients later proven to have recurrent lung cancer in the ablation zone. In the recurrence group there was a peak of enhancement seen with rapid washout. Specifically ,at 1 month the mean attenuation of the ablation zone in the recurrence group was 10 HU pre-contrast with a peak in attenuation of 35 HU at 1 minute with an attenuation of 18 HU at 4 minutes. The non-recurrence group showed a mean attenuation of -13HU pre-contrast and a peak attenuation of 47 HU at 4 minutes the mean peak attenuation. Similar findings were seen at each 3, 6 and 12 moth follow-up CT scans. Using a paired-samples student t-test, there was no statically significant difference in the change in attenuation .

The absolute change in attenuation is a poor discriminator of recurrence from non-recurrence. However, there is a difference in the pattern of enhancement. The patients with evidence of recurrence showed an early peak in enhancement and then a washout of contrast. While patients without recurrence showed continued increase in attenuation over time. This is similar to the patterns seen in other malignancies comparing malignancy to inflammatory masses.

Enhancement pattern changes associated with treatment of lung cancer with SABR may assist in evaluating potential early recurrence where a change in treatment can most affect prognosis.

Moore, W, Chaudhry, A, Chaya, Y, Bilfinger, T, Glass, S, Gaur, S, Mikhail, G, Baker, K, Kim, B, CT Nodule Enhancement Pattern in Patients after SABR.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14006847.html