A retrospective study analyzing missed diagnosis of lung metastases at their early stages on computed tomography

Abstract

Background: Lungs are one of the target organs of metastases of primary lung, breast, liver, colorectal, and esophageal cancer. While computed tomography (CT) is the most widely used modality for detecting lung metastases, it is still very challenging to detect them at the earlier stages. If lung metastases could be found on CT scans at the earliest time points, patients would benefit by beginning treatment earlier. The objective of this study was to demonstrate that CT can reveal lung metastases in many cases at even earlier stages than current radiological practice may find.

Methods: One hundred patients with lung metastases were randomly selected and their surveillance CT scans were analyzed retrospectively. The patients had primary cancer in the breasts, lungs, esophagus, colorectum, and liver. All patients had multiple CT examinations of the lungs and their metastases, if any, were confirmed by subsequent CT scans. The earliest CT scans were examined to determine whether lung metastases at the same locations had been diagnosed or missed. Missed lung metastases, categorized by type of the primary cancer and adjacency to nearby blood vessels, were statistically analyzed.

Results: There were 36/100 (36%) cases of missed lung metastases, including 15 cases of single metastasis and 21 cases of multiple metastases. There were a total of 174 missed loci of lung metastases. Where metastases were missed, there was a statistically significant difference (P<0.001) in their distribution within the sub-regions of the lungs. Adjacency to blood vessels appeared to be a significant factor in metastases being missed during diagnosis (P<0.001).

Conclusions: There was a considerable percentage of early lung metastases that were missed by radiologists but actually appeared on CT scans. The capability of CT to reveal such early metastases opens up an opportunity to move up the time points of detecting lung metastases through clinical and training improvement and technology development such as computer-aided detection.

Keywords: Computed tomography (CT); early detection; lung metastases.

Figure 1

Two cases of missed nodules and their outcomes. (A,C,E) A case of a 63-year-old breast cancer patient with a missed nodule detection at the initial CT scan. (A) A missed nodule (arrow) on the first scan. The nodule was found only after mapping the position of the detected nodule (arrow) on the second scan 7 months later (C) to the first scan. (E) After chemotherapy, the nodule (arrow) was seen becoming smaller on the third scan performed another 5 months later. (B,D,F) A case of a 53-year-old breast cancer patient. The initial scan (B) was truly negative. Eight months later two nodules (arrows) were detected on the second scan (D). An additional 12 months later, the nodules (arrows) were significantly larger and a new nodule was found on the third scan (F).

Figure 2

A case of a 46-year-old male liver cancer patient. (A) The metastasis was missed by a radiologist (arrow) on the first scan; (B) the metastasis, with an increased size, was found by a radiologist on the second scan at 4 months late (arrow).

Figure 3

Sizes (in diameter) of the 174 missed pulmonary nodules measured on HRCT. Mean diameter of the nodules was 2.66 mm in diameter (broken line). Minimum and maximum diameters were 0.67 and 7.60 mm, respectively. HRCT, high-resolution computed tomography.

Figure S1

Division of the lungs into the upper, center, and lower regions.

Figure S2

Division of the lungs into the inner, middle, and outer regions.