Added value and clinical impact of second-opinion subspecialist radiologist interpretations of baseline rectal MRI in patients with rectal cancer

Abstract

Objectives: To evaluate the completeness and discordance of outside rectal MRI initial staging reports compared to second-opinion reviews, and to assess the potential clinical impact of major discordance on treatment decisions in patients with rectal adenocarcinoma.

Materials and methods: A retrospective analysis of outside rectal MRI reviews submitted for second-opinion interpretation by subspecialized radiologists from June 2014-March 2020 was conducted. Outside and second review reports were compared side-by-side; cases with discordance (and those with major discordance, i.e., may alter treatment, particularly) were identified. Two colorectal surgeons, blinded to report origins, reviewed cases with major discordance to evaluate their theoretical impact on patient management and rated their confidence level of the reports on a five-point Likert scale (1=lowest confidence).

Results: In 461 patients (median age, 57 years [IQR: 49-67]; 274 male), compared to outside reviews, second reviews demonstrated improved report completeness across tumor characteristics, local extent, and nodal/metastatic disease clinical staging categories. The largest reporting gaps were in tumor morphology (66.4%, 306/461 vs. 98.7%, 455/461) and extramural venous invasion (29.1%, 134/461 vs. 93.9%, 433/461). Overall, 53.8% (248/461) of cases showed discordance, with 56.5% (140/248) classified as major. In this subset, second reviews led to fewer cases with insufficient information, e.g., 18.6% (26/140) to 7.1% (10/140) for Surgeon 1, and changes in surgical planning in 38.1-46.3% (43/113 to 44/95) of patients. Surgeons rated reports from second reviews with higher confidence scores (median, 4 vs. 2-3, p < 0.001).

Conclusions: Second-opinion reviews may impact patient care and improve surgeons' confidence for treatment planning.

Key points: Question Do subspecialist radiologist second-opinion reviews improve rectal MRI report completeness and affect treatment decisions in rectal adenocarcinoma staging? Findings While outside reviews often under-reported key imaging findings, second reviews improved report completeness, which led to increased confidence by our surgeons in treatment planning. Clinical relevance These findings underscore the value of expert interpretation and highlight the need for optimized MRI protocols and broader adoption of structured reporting in rectal cancer staging.

Keywords: Rectal adenocarcinoma; Rectal neoplasms; Second-opinion; Treatment planning; Tumor staging.

Fig. 1

Study inclusion flow

Fig. 2

Completeness of reporting elements: outside vs. second review. Comparison of reported MRI elements between outside and second reviews. Bars represent the number of reports that included (“Reported”) or did not include (“Not reported”) each element, stratified by outside vs. second review. Percentages indicate the proportion of reports in which the element was reported. Elements shown in bold indicate a statistically significant difference in reporting frequency between outside and second reviews. Abbreviations: ARJ = anorectal junction, AV = anal verge, APR = anterior peritoneal reflection, MRF = mesorectal fascia, EMD = extramural depth of invasion, EMVI = extramural venous invasion

Fig. 3

Discordant rates of categorical reporting elements: outside vs. second review. Discordant rates between outside radiology reports and internal second reviews across categorical reporting elements. The horizontal bar chart displays the percentage of discordance for each element, defined as discordance between the outside and second review findings. Discordant rates are labeled as percentages with absolute counts. Abbreviations: APR = anterior peritoneal reflection, EMVI = extramural venous invasion

Fig. 4

Example of major discordance between the outside review and second review in a 35-year-old male patient with rectal adenocarcinoma undergoing initial staging MRI. (A–D) MRI lacked oblique and small field-of-view images. (A) Sagittal T2-weighted imaging shows a circumferential mid-to-upper rectal tumor (white arrow), 7.7 cm from the AV. (B, C) EMVI (dotted arrow) and suspicious intramesorectal nodal metastases (arrowheads) are seen. Summary table shows that tumor location, T category, and EMVI were not mentioned in the outside report. APR = abdominoperineal resection; ARJ = anorectal junction; AV = anal verge; EMVI = extramural venous invasion; MRF = mesorectal fascia

Fig. 5

Example of major discordance between the outside review and second review in a 62-year-old female patient with rectal adenocarcinoma undergoing initial staging MRI. (A) Sagittal T2-weighted imaging shows a circumferential low rectal tumor with anal canal involvement (arrowheads) and suspected anterior extension to the posterior vaginal wall (arrow). (B) Right obturator adenopathy (dotted arrow). (C) Coronal T2-weighted imaging shows involvement of the left levator ani muscle (arrowheads). Summary table shows discordance in T category and primary tumor description between the outside review and the second review. The outside review described levator ani involvement but assigned T3c category and misidentified the extramesorectal node as an external iliac node. These findings were correctly reported in the second review.

Fig. 6

The number of elements cited as informing treatment decisions in each report. Second review consistently provided more complete information than outside review across nearly all categories, except for anal verge distance (Surgeon 1) and tumor morphology (both surgeons)