Interobserver Variability in CT-based Morphologic Tumor Response Assessment of Colorectal Liver Metastases

Abstract

Purpose To evaluate interobserver variability in the morphologic tumor response assessment of colorectal liver metastases (CRLM) managed with systemic therapy and to assess the relation of morphologic response with gene mutation status, targeted therapy, and Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 measurements. Materials and Methods Participants with initially unresectable CRLM receiving different systemic therapy regimens from the randomized, controlled CAIRO5 trial (NCT02162563) were included in this prospective imaging study. Three radiologists independently assessed morphologic tumor response on baseline and first follow-up CT scans according to previously published criteria. Two additional radiologists evaluated disagreement cases. Interobserver agreement was calculated by using Fleiss κ. On the basis of the majority of individual radiologic assessments, the final morphologic tumor response was determined. Finally, the relation of morphologic tumor response and clinical prognostic parameters was assessed. Results In total, 153 participants (median age, 63 years [IQR, 56-71]; 101 men) with 306 CT scans comprising 2192 CRLM were included. Morphologic assessment performed by the three radiologists yielded 86 (56%) agreement cases and 67 (44%) disagreement cases (including four major disagreement cases). Overall interobserver agreement between the panel radiologists on morphology groups and morphologic response categories was moderate (κ = 0.53, 95% CI: 0.48, 0.58 and κ = 0.54, 95% CI: 0.47, 0.60). Optimal morphologic response was particularly observed in patients treated with bevacizumab (P = .001) and in patients with RAS/BRAF mutation (P = .04). No evidence of a relationship between RECIST 1.1 and morphologic response was found (P = .61). Conclusion Morphologic tumor response assessment following systemic therapy in participants with CRLM demonstrated considerable interobserver variability. Keywords: Tumor Response, Observer Performance, CT, Liver, Metastases, Oncology, Abdomen/Gastrointestinal Clinical trial registration no. NCT02162563 Supplemental material is available for this article. © RSNA, 2022.

Keywords: Abdomen/Gastrointestinal; CT; Liver; Metastases; Observer Performance; Oncology; Tumor Response.

Graphical abstract

Figure 1:

Flow diagram of selection study sample for morphologic tumor response assessment. CLRM = colorectal liver metastases.

Figure 2:

Morphologic response categories. Baseline and follow-up CT scans show (A, B) an optimal morphologic response of colorectal liver metastases with the transition of heterogeneous attenuation and ill-defined tumor–liver interface (A) to homogeneous and hypoattenuating attenuation and sharp tumor–liver interface (B) and (C, D) suboptimal morphologic response with the transition of heterogeneous attenuation and ill-defined tumor–liver interface (C) to homogeneous attenuation but ill-defined tumor–liver interface remaining after treatment (D).

Figure 3:

Distribution of the morphology group assignments according to baseline CT scan (n = 153) and follow-up CT scan (n = 153) performed by the three radiologists.

Figure 4:

Distribution of the morphologic tumor response assessments (n = 153) performed by the three radiologists.

Figure 5:

Distribution of the morphologic tumor response assessments of the disagreement cases (n = 67) performed by the additional two radiologists.

Figure 6:

Bar chart depicts the morphologic tumor response assessment of the 67 disagreement cases of the three radiologists and the assessment by the two additional radiologists involved only in the disagreement cases’ assessment. Each bar represents one participant. The chart depicts the percentages of radiologists’ assessment for classifying participants as optimal morphologic response (blue), suboptimal morphologic response (orange), and no morphologic response (dark blue). Based on the majority of votes, 58 cases were solved and nine cases remained unsolved.