Magnetic resonance imaging accuracy in assessing tumour down‐staging following chemoradiation in rectal cancer

Abstract

Objective Magnetic resonance imaging (MRI) is increasingly accepted as the radiological modality of choice staging rectal cancer but is subject to error. Neoadjuvant therapy is increasingly used in rectal cancer and MRI is used to stage response and occasionally plan surgery. We aim to assess the staging accuracy of MRI following chemoradiotherapy in rectal cancer.Method Retrospective analysis of 86 patients with MRI stage pre-and postlong-course chemoradiotherapy and comparison with pathological assessment.Results Fourty-nine patients (34 men, 15 women) with median age 68 years (60-74) were analysed. The median time from completion of CRT to MRI was 32 days (16-37). Chemoradiotherapy led to significant down-staging (P < 0.001). MRI-staging accuracy was 43% (21 ⁄ 49) with over-and under-staging in 43% (21 ⁄ 49) and 14% (7 ⁄ 49) respectively. T-stage accuracy was 45% (22 ⁄ 49) with overstaging in 33% (16 ⁄ 49) and under-staging in 22% (11 ⁄ 49).MRI stage correlated poorly with pathological assessment for International Union Against Cancer (j = 0.255) and T stages (j = 0.112). MRI nodal assessment was 71% (35 ⁄ 49) accurate, with 82% (9 ⁄ 11) sensitivity, 68% (26 ⁄ 38) specificity and positive predictive value (PPV) of 43% (9 ⁄ 21) and negative predictive value of 93% (26 ⁄ 28). There was a significant difference in node positivity between MRI and pathological staging (P = 0.005, Fisher's exact). Complete radiological response was observed in 4% (2 ⁄ 49). Complete pathological response was observed in 10% (5 ⁄ 49), which were staged 0(1), I(1), II(2) and III(1) postchemoradiotherapy by MRI.Conclusion MRI staging following chemoradiation is poor. Over-staging occurs three times more commonly than under-staging. Over-staging is due to poor PPV of nodal assessment.

Oncologic Outcomes according to the Treatment Strategy in Radiologic Complete Responders after Neoadjuvant Chemoradiation for Rectal Cancer

“…These findings also may have affected oncologic outcomes. Although the MERCURY group believes that MRI after nCRT should be mandatory and is very helpful in predicting pathologic T stage and prognosis [7], others argue that MR reimaging after nCRT is of limited value because of its low accuracy [25,26,27]. The MERRION study, in particular, showed that the positive predictive value [18.2% (2/11)] and κ statistics (0.021) of MRI were very poor in predicting pathologic CR [25].…”

Application of Endorectal Ultrasound in Evaluation of Anorectal Diseases

“…Many studies have proved that ERUS is still the most accurate method to determine neoplastic wall infiltration and lymph node involvement even after RCT [78,79] . After neoadjuvant treatment, the status of the lymph nodes remains a problem; ERUS and MRI both have a low accuracy to evaluate metastatic lymph nodes after neoadjuvant [80] . For the correctly restaging rectal cancer after neoadjuvant treatment, it is of vital important to choose the correct time between the end of neoadjuvant therapy and the procedure of ERUS.…”

Is the Standardized Uptake Value of FDG-PET/CT Predictive of Pathological Complete Response in Locally Advanced Rectal Cancer Treated with Capecitabine-Based Neoadjuvant Chemoradiation?

“…The TRG score accurately reflects the variation in the biological response to radiation, also in the absence of T stage change [25]. The common methods for monitoring the tumor response to neoadjuvant CRT, such as physical examination and conventional imaging modalities, have several limitations due to the difficulties in the distinction between disease persistence and treatment-induced fibrosis [9]. Up to 75% of patients who appear to have obtained a clinical complete response still have microscopic disease at the time of full thickness biopsy [26,27].…”

“…The achievement of downstaging or pathological complete response (pCR) after neoadjuvant CRT is correlated with improved survival, decreased local recurrence, and higher chances of sphincter-preserving surgeries [4,5,6,7]. Conventional imaging modalities, including CT, MRI, and endoscopic ultrasound, have shown promise in monitoring the response to neoadjuvant CRT [8,9,10]. However, these techniques rely on the documentation of morphological changes, with limited accuracy and reproducibility in determining clinical downstaging and distinguishing viable tumor from fibrotic tissue.…”