Date Published: January 25, 2019
Publisher: Public Library of Science
Author(s): Chul Hwan Park, Tae Hoon Kim, Sungsoo Lee, Duk Hwan Moon, Heae Surng Park, Atsushi Miyamoto.
The authors compared maximal tumor diameters between fresh lung tissue and axial and multiplanar reformatted chest computed-tomography (CT) images in lung adenocarcinoma and investigated the factors affecting tumor-size discrepancies. This study included 135 surgically resected lung adenocarcinomas. An experienced pulmonary pathologist aimed to cut the largest tumor section and measured pathological tumor size (PTS) in fresh specimens. Radiological maximal tumor sizes (RTS) were retrospectively measured on axial (RTSax) and multiplanar reformatted (RTSre) chest CT images. Mean PTS, RTSax, and RTSre were 19.13 mm, 18.63 mm, and 20.80 mm, respectively. RTSre was significantly larger than PTS (mean difference, 1.68 mm; p<0.001). RTSax was also greater than PTS for 6−10-mm and 11−20-mm tumors. PTS and RTS were strongly positively correlated (RTSax, r2 = 0.719, p<0.001; RTSre, r2 = 0.833, p<0.001). The intraclass correlation coefficient was 0.915 between PTS and RTSax and 0.954 between PTS and RTSre. Postoperative down-staging occurred in 11.0% and 27.4% of tumors on performing radiological staging using RTSax and RTSre, respectively. Postoperative up-staging occurred in 12.3% and 1.4% of tumors on performing radiological staging using RTSax and RTSre, respectively. Multiple linear regression revealed that pleural dimpling (p = 0.024) was an independent factor affecting differences between PTS and RTSax. Specimen type (p = 0.012) and tumor location (p = 0.020) were independent factors affecting differences between PTS and RTSre. In conclusion, RTSre was significantly larger than PTS and caused postoperative down-staging in 27.4% of the tumors. Reliability analysis revealed that RTSre was more strongly correlated with PTS than RTSax. Specimen type and anatomical tumor location influenced the measured size differences between PTS and RTSre.
Tumor size is an important prognostic factor in cancers of solid organs. There are, however, discrepancies in tumor size measured using pathological and radiological methods. In renal tumors, computed tomography (CT) of radiological tumor size (RTS) generally overestimates pathological tumor size (PTS)[1, 2]. In non-small cell lung cancer (NSCLC), chest CT usually overestimates PTS[3–5]; however, conflicting results have been reported. Lung tumor size discrepancies between radiological and pathological methods are affected by several factors. First, the degree of lung aeration and expansion when measuring PTS and RTS is quite different. In lung cancer, RTS is usually measured in the fully expanded condition when the patient holds a deep breath. However, PTS is measured with the lung in the collapsed condition, when it is compressed during one-lung ventilation for surgery, and the resected lung tissue becomes more flat due to deflation and blood drainage after removal of surgical clip(s) or staples(s)[3, 5]. Second, the tumor planes in CT and specimens, where the maximal tumor size is measured, are different. For example, radiologists usually measure tumor size in the axial plane of chest CT, unless the tumor extends vertically lengthwise. However, pathologists tend to cut the largest tumor section perpendicular to the visceral pleura and resected surface to assess pleural invasion and resection margin, and then measure tumor size. If the tumor shape is vertically long, the axial plane of chest CT may underestimate tumor size compared with sagittal or coronal planes of CT, or pathology specimen.
A total of 135 tumors from 128 patients were included in the study. Mean time interval between CT scan and surgery was 17 days (range, 0–91). Demographic data from the study population are summarized in Table 1. Mean (± standard deviation) PTS, RTSax, and RTSre were 19.13±9.41 mm, 18.63±8.60 mm, and 20.80±9.46 mm, respectively. Mean RTSre was significantly larger than PTS (mean difference, 1.68±3.94 mm; p<0.001); however, there was no significant difference between RTSax and PTS (mean difference, 0.49±5.31 mm; p = 0.285). When tumors were divided into 10-mm intervals, the mean RTS (both RTSax and RTSre) was significantly greater than the mean PTS for tumors in 6–10 mm and 11–20 mm categories, and the mean difference was greater in RTSre than in RTSax (Table 2). For tumors in the 21–30 mm category, RTSax was significantly larger than PTS. However, PTS was significantly larger than RTSax for tumors in the 41–50 mm category. In the remaining categories, there was no significant difference between PTS and RTS. Tumor size became a very important prognostic descriptor for NSCLC in the American Joint Committee on Cancer Staging Manual, 8th Edition. For T staging purposes in lung cancer, the manual defines RTS as the single largest tumor dimension measured on axial, coronal, or sagittal CT sections at the lung window setting[14, 15]. Measurement of PTS is recommended to be performed in fresh specimens after cross-sectioning[9, 16]. As the longest tumor axis does not always align with axial, coronal, or sagittal planes, we also evaluated the RTS in obliquely reconstructed CT images in this study. In addition, as measuring tumor size in a cut section of fresh lung tissue is not a routine practice in pathology, we specifically designed the study cohort to measure PTS in the fresh state using the same cutting methodology. Source: http://doi.org/10.1371/journal.pone.0211141