Implications of previously undetected incidental findings on 3D CT simulation scans for radiation therapy

To determine the frequency of significant incidental findings on diagnostic quality simulation computed tomographic (CT) scans for radiotherapy planning.

An institutional review board--approved retrospective review of radiation simulation CT scans with diagnostic radiology reports, performed between 2004 and 2006, was conducted to identify incidental findings, defined as previously unreported findings. An incidental finding was classified as a cancer-related finding (CRF) if it could potentially change the staging and treatment of the cancer. Other nonmalignant findings, not likely caused by cancer, were classified as noncancer findings (NCFs).

Of the 580 CT scans performed for radiation planning, 61 (11%) NCFs and 45 (8%) CRFs were identified. Common NCFs included degenerative bone changes (20%), diverticulosis (15%), and lung (11%), kidney (10%), thyroid (10%), and vascular (7%) abnormalities. Two of the vascular NCFs were thrombi requiring anticoagulation. The CRFs included suspected local recurrence (22%); lymphadenopathy (18%); significant progression of local disease (16%); distant metastasis to the liver (16%), bone (11%), and other sites (16%); and malignancy not evident (2%). Eight CRFs prompted additional workup, all with negative results, causing 2 treatment delays. Three CRFs warranted change of treatment without further imaging, including the use of induction chemotherapy before radiation, an increase in radiation dose, and proceeding with surgery up front followed by radiation. The remaining 34 CRFs did not require additional action because the abnormalities were already addressed by the planned treatment (33%), were believed to be benign with further review (29%), or would have been better evaluated by additional imaging that had been scheduled prior to radiation simulation (13%). Overall, 7 of 580 (1%) scans prompted treatment alterations, including 2 treatment delays.

A comprehensive review of radiation planning CT scans by diagnostic radiologists resulted in a significant change in medical or cancer management in only a small percentage of cases.