Circumferential resection margins of rectal tumours post-radiotherapy: how can MRI aid surgical planning?

Prognostic factors for local recurrence in patients with rectal cancer submitted to neoadjuvant chemoradiotherapy and total mesorectal excision

Prognostic factors for local recurrence in patients with rectal cancer submitted to neoadjuvant chemoradiotherapy and total mesorectal excision.

BACKGROUND

The standard curative treatment for locally advanced rectal cancer of the middle and lower thirds is long-course chemoradiotherapy followed by total mesorectal excision.

PURPOSE

To evaluate the prognostic factors associated with local recurrence in patients with rectal cancer submitted to neoadjuvant chemoradiotherapy and total mesorectal excision.

METHODS

Retrospective study including patients with rectal cancer T3-4N0M0 or T (any)N + M0 located within 10 cm from the anal border, or patients with T2N0M0 located within 5 cm, treated by long course chemoradiotherapy followed by total mesorectal excision with curative intent. Clinical, demographic, radiologic, surgical, and anatomopathological data were collected. Local recurrence was estimated using the Kaplan-Meier function, and risk was estimated according to each characteristic using univariate and multivariate analyses.

RESULTS

270 patients were included, 57.8% male and mean age 61.7 (30‒88) years. At initial staging, 6.7% of patients were stage I, 21.5% stage II, and 71.8% stage III. Open surgery was performed in 65.2%, with sphincter preservation in 78.1%. Mortality within 30 postoperative days was 0.7%. After 49.4 (0.5‒86.1) months of median follow-up, overall and local recurrences were 26.3% and 5.9%. On multivariate analyses, local recurrence was associated with involvement of the mesorectal fascia on restaging MRI (HR = 9.11, p = 0.001) and with pathologic involvement of radial surgical margin (HR = 8.19, p < 0.001).

CONCLUSION

Local recurrence of rectal cancer treated with long-course chemoradiation and total mesorectal excision is low and is associated with pathologic involvement of the radial surgical margin and can be predicted on restaging MRI.

Progress of MRI in predicting the circumferential resection margin of rectal cancer: A narrative review

Rectal cancer (RC) is the third most frequently diagnosed cancer worldwide, and the status of its circumferential resection margin (CRM) is of paramount significance for treatment strategies and prognosis. CRM involvement is defined as tumor touching or within 1 mm from the outermost part of tumor or outer border of the mesorectal or lymph node deposits to the resection margin. The incidence of involved CRM varied from 5.4 % to 36 %, which may associate with an in consistent definition of CRM, the quality of surgeries, and the different examination modalities. Although T and N status are essential factors in determining whether a patient should receive neoadjuvant therapy before surgery, CRM status is a powerful predictor of local and distant recurrence as well as survival rate. This review explores the significance of CRM, the various assessment methods, and the role of magnetic resonance imaging (MRI) and artificial intelligence-based MRI in predicting CRM status. MRI showed potential advantage in predicting CRM status with a high sensitivity and specificity compared to computed tomography (CT). We also discuss MRI advancements in RC imaging, including conventional MRI with body coil, high-resolution MRI with phased-array coil, and endorectal MRI. Along with a discussion of artificial intelligence-based MRI techniques to predict the CRM status of RCs before and after treatments.

Predicting Positive Radial Margin on Restaging MRI of Patients with Low Rectal Cancer: Can We Do Better?

Objective  The aim of this study was to characterize the tissue involving the margin and study if this information will affect margin prediction on restaging magnetic resonance imaging (MRI) in low rectal adenocarcinoma (LRC) patients treated with neoadjuvant long-course chemoradiotherapy (LCCRT). Methods  In this retrospective study of nonmetastatic LRC (distal margin <5 cm from the anal verge) treated with LCCRT followed by surgery, a radiologist blinded to outcome reread the restaging MRI and documented if the radial margin was involved by tumor, fibrosis, or mucin reaction using T2 high-resolution (HR) and diffusion-weighted imaging (DWI). The diagnostic performance of tumor-involving margin on restaging MRI was assessed using surgical histopathology as a reference. Interobserver agreement between three independent radiologists was assessed in a subset. Results  We included 133 patients (80 males and 53 females) with a mean (range) age of 44.7 (21-86) years and 82% of them had well or moderately differentiated adenocarcinoma. Baseline MRI showed T3 ( n  = 58) or T4 ( n  = 60) disease in 89% of the patients. The pathological margin was positive in 21% ( n  = 28) cases. In restaging MRI, the circumferential resection margin (CRM) ≤1 mm in 75.1% ( n  = 100) cases and MRI predicted tumor, fibrosis, and mucin reaction at the margin in 60, 34, and 6%, respectively, and histopathology showed tumor cells in 33, 14.7, and 16.6% of them, respectively. LRC with tumor-involving margin and bad response (MR tumor regression grade [mr-TRG] 3-5) on restaging MRI had fourfold increased risk of positive pathological circumferential resection margin (pCRM). There was moderate and fair inter-reader agreement for the tissue type involving the CRM ( κ  = 0.471) and mr-TRG ( κ  = 0.266), p  < 0.05. The use of both distance criteria and tumor-involving margins improved the diagnostic accuracy for margin prediction from 39 to 66% on restaging MRI. Conclusions  Margin prediction on restaging MRI can be improved by characterizing the tissue type involving the margin in low rectal cancer patients. The inter-reader agreement was moderate for determining the tissue type.

Downstaging in Advanced Rectal Cancers: A Propensity-Matched Comparison Between Short-Course Radiotherapy Followed by Chemotherapy and Long-Course Chemoradiotherapy

BACKGROUND

Short-course radiotherapy followed by chemotherapy has not been widely evaluated as an alternative to traditional long-course chemoradiotherapy in locally advanced rectal cancer.

OBJECTIVE

This study compared the oncological and short-term outcomes between short-course radiotherapy + chemotherapy and long-course chemoradiotherapy in locally advanced rectal cancer.

DESIGN

This is a retrospective propensity-matched study.

SETTINGS

The study was conducted in a colorectal department at a tertiary care oncology center in India.

PATIENTS

There were 173 patients. Group A had 47 patients and group B had 126 patients. A 1:2.7 matching was done for age, sex, distance of tumor from the anal verge, sphincter preservation surgeries, MRI-based pretreatment T stage, and circumferential resection margin.

INTERVENTIONS

The interventions performed were short-course radiotherapy + chemotherapy (group A) and long-course chemoradiotherapy (group B) in locally advanced rectal cancer.

MAIN OUTCOME MEASURES

The primary measures were pathological circumferential resection margin positivity, downstaging, tumor regression grade, and postoperative complications.

RESULTS

Of the patients, 52% had a positive circumferential resection margin on MRI, 57% had low rectal tumors, and 20% had T4 tumors. Distribution of rectal surgeries was similar between the 2 groups. pT downstaging and tumor regression scores were significantly better in group B ( p = 0.028 and 0.026). Pathological circumferential resection margin, distal resection margin, and nodal yield were similar. On multivariate analysis, pretreatment N status was the only independent predictive factor for pathological circumferential resection margin status. Grade 3 to 4 Clavien-Dindo complications, anastomotic leak rates, and hospital stay were similar between the 2 groups.

LIMITATIONS

This was a retrospective study. Although propensity matching was performed, selection bias cannot be eliminated completely, as seen in the difference in the surgical approaches between the 2 groups.

CONCLUSIONS

In a cohort containing a significant portion of MRI circumferential resection margin-positive low rectal cancers, short-course radiotherapy + chemotherapy followed by delayed surgery resulted in lower T downstaging and lower tumor regression scores compared with long-course chemoradiotherapy, but pathological circumferential margin status, distal resection margin, nodal yield, and perioperative morbidity were similar between the 2 groups. This suggests that short-course radiotherapy + chemotherapy could be a viable alternative to long-course chemoradiotherapy in locally advanced rectal cancers. See Video Abstract at http://links.lww.com/DCR/B855 .

REDUCCIN DEL ESTADIO EN LOS CNCERES RECTALES AVANZADOS UNA COMPARACIN DE PROPENSIN EQUIPARADA ENTRE LA RADIACIN DE CICLO CORTO SEGUIDA DE QUIMIOTERAPIA Y LA QUIMIO RADIACIN DE CICLO LARGO

ANTECEDENTES:La radioterapia de ciclo corto seguida de quimioterapia no ha sido evaluada ampliamente como una alternativa a la tradicional quimio radioterapia de ciclo largo en el cáncer de recto localmente avanzado.OBJETIVO:Estudio que compara los resultados oncológicos y a corto plazo entre la radioterapia de ciclo corto + quimioterapia y la quimio radioterapia de ciclo largo en el cáncer de recto localmente avanzado.DISEÑO:Estudio comparado de propensión de manera retrospectiva.AJUSTE:Departamento colorrectal en un centro de atención oncológica de tipo terciario en la India.PACIENTES:Hubo 173 pacientes. El grupo A tenía 47 y el grupo B tenía 126 pacientes. Se realizó una comparación de 1: 2,7 para edad, sexo, distancia del tumor desde el margen anal, cirugías de preservación del esfínter, estadio T previo al tratamiento basada en resonancia magnética y margen de resección circunferencial (CRM).INTERVENCIONES:Radioterapia de ciclo corto + quimioterapia (grupo A) y quimio radioterapia de ciclo largo (grupo B) en cáncer de recto localmente avanzado (LARC).PRINCIPALES MEDIDAS DE RESULTADO:Positividad histopatológica de CRM, reducción del estadio tumoral, grado de regresión tumoral, complicaciones posoperatorias.RESULTADOS:El 52% de los pacientes han tenido un margen de resección circunferencial positivo en la resonancia magnética, 57% de tumores rectales bajos, 20% de tumores T4. La distribución de cirugías rectales fue similar entre los 2 grupos. Las puntuaciones de regresión tumoral y de reducción del estadio de pT fueron significativamente mejores en el grupo B ( p = 0.028 y 0.026 respectivamente). El margen de resección circunferencial patológico, el margen de resección distal y los ganglios arrojados fueron similares. En el análisis multivariado, el estadio N previo al tratamiento fue el único factor predictivo independiente para el estadio de pCRM. Las complicaciones Clavien-Dindo de grado 3-4, las tasas de fuga anastomótica y la estancia hospitalaria fueron similares entre los dos grupos.LIMITACIONES:Retrospectiva; aunque la propensión coincide, existe potencial sesgo de selección.CONCLUSIONES:En una cohorte que contenía una porción significativa de cánceres rectales bajos con margen de resección circunferencial positivo por resonancia magnética, la radioterapia de ciclo corto + quimioterapia seguida de cirugía tardía dio como resultado una mayor reducción del estadio T y de regresión tumoral en comparación con la quimio radioterapia de ciclo largo. Pero el estatus histopatológico del margen circunferencial, el margen de resección distal, el rendimiento ganglionar y la morbilidad perioperatoria fueron similares entre los dos grupos. Esto sugiere que la radioterapia de ciclo corto + quimioterapia podría ser una alternativa viable a la quimio radioterapia de ciclo largo en cánceres rectales localmente avanzados. Consulte Video Resumen en http://links.lww.com/DCR/B855 . (Traducción-Dr. Osvaldo Gauto ).

MRI at Restaging After Neoadjuvant Therapy for Rectal Cancer Overestimates Circumferential Resection Margin Proximity as Determined by Comparison With Whole-Mount Pathology

BACKGROUND

Current guidelines recommend restaging with MRI after neoadjuvant therapy for rectal cancer, but the accuracy of restaging MRI in estimating circumferential margin involvement requires additional clarification.

OBJECTIVE

The objective of this study was to measure the accuracy of circumferential resection margin assessment by MRI after neoadjuvant therapy and identify characteristics associated with accuracy.

DESIGN

MRI data were retrospectively analyzed for concordance with the findings of whole-mount pathology analysis of the corresponding surgical specimens. Univariate and multivariate logistic regression analyses were performed to identify characteristics associated with accuracy.

SETTING

This study was conducted at a comprehensive cancer center.

PATIENTS

Included in the study were consecutive patients who underwent total mesorectal excision for rectal cancer between January 2018 and March 2020 after receiving neoadjuvant therapy and undergoing restaging with MRI.

MAIN OUTCOME MEASURES

The primary outcome of this study included accuracy, sensitivity, specificity, and positive and negative predictive values for categorizing the circumferential resection margin as threatened; mean and paired mean differences were in proximity of the margin.

RESULTS

Of the 94 patients included in the analysis, 39 (41%) had a threatened circumferential resection margin according to MRI at restaging, but only 17 (18%) had a threatened margin based on pathology. The accuracy of MRI in identifying a threatened margin was 63.8%, with margin proximity overestimated by 0.4 cm on average. In multivariate logistic regression, anterior location of the margin and tumor proximity to the anal verge were independently associated with reduced MRI accuracy.

LIMITATIONS

A limitation was the retrospective design at a single institution.

CONCLUSIONS

The knowledge that MRI-based restaging after neoadjuvant therapy overestimates circumferential margin proximity may render some surgical radicality unnecessary and thereby help avoid the associated morbidity. With the recognition that MRI-based assessment of margin proximity may not be reliable for anterior margin and for distal tumors, radiologists may want to use greater caution in interpreting images of tumors with these characteristics and to acknowledge the uncertainty in their reports. See Video Abstract at http://links.lww.com/DCR/B814.

LA IRM EN LA REESTADIFICACIN LUEGO DE TERAPIA NEOADYUVANTE EN EL CNCER DE RECTO SOBRESTIMA LA PROXIMIDAD DEL MARGEN DE RESECCIN CIRCUNFERENCIAL SEGN LO DETERMINADO COMPARATIVAMENTE CON LA PIEZA DE ANATOMOPATOLOGA

ANTECEDENTES:Las pautas actuales recomiendan la re-estadificación por medio de la resonancia magnética luego de terapia neoadyuvante en los casos de cáncer de recto, pero la precisión de la reevaluación con la IRM para estimar el grado de implicación del margen circunferencial requiere aclaraciones adicionales.OBJETIVO:Medir el grado de exactitud en la evaluación del margen de resección circunferencial mediante resonancia magnética después de la terapia neoadyuvante e identificar las características asociadas con la precisión.DISEÑO:Se analizaron retrospectivamente los datos de resonancia magnética para determinar la concordancia entre los hallazgos del análisis de la pieza de anatamopatología y las muestras quirúrgicas correspondientes. Se realizó el análisis de regresión logística univariada y multivariada para identificar las características asociadas con la exactitud.AJUSTE:Centro oncológico integral.PACIENTES:Todos aquellos que se sometieron consecutivamente a una excisión total del mesorrecto por cáncer rectal entre Enero 2018 y Febrero 2020 luego de recibir terapia neoadyuvante y someterse a una re-estadificación por imágenes de resonancia magnética (IRM).PRINCIPALES MEDIDAS DE RESULTADO:La exactitud, la sensibilidad y especificidad; los valores predictivos positivos y negativos para categorizar el margen de resección circunferencial como amenazado; la diferencia media y las medias pareadas de proximidad a los margenes.RESULTADOS:De los 94 pacientes incluidos en el análisis, 39 (41%) tenían un margen de resección circunferencial amenazado según la resonancia magnética en la re-estadificación, pero solo 17 (18%) tenían un margen amenazado basado en la patología. La precisión de la resonancia magnética para identificar un margen amenazado fue del 63,8%, con la proximidad del margen sobreestimada en 0,4 cm en promedio. En la regresión logística multivariada, la ubicación anterior de los bordes de resección y la proximidad del tumor al margen anal se asociaron de forma independiente con la reducción en la precisión de la resonancia magnética.LIMITACIONES:Diseño retrospectivo en una institución única.CONCLUSIONES:El saber que la re-estadificación basada en la IRM, luego de terapia neoadyuvante sobreestima la proximidad de la lesión a los márgenes circunferenciales, hace innecesaria cierta radicalidad quirúrgica complementaria, lo que ayuda a evitar morbilidad asociada. Reconociendo que la evaluación de proximidad de los márgenes de resección basada en la resonancia magnética, no puede ser confiable en casos de márgenes anteriores y en casos de tumores distales. Los radiólogos recomiendan tener más precaución en la interpretación de imágenes de tumores con estas características y reconocen cierto desasosiego en sus informes. Consulte Video Resumen en http://links.lww.com/DCR/B814.

Can CRM Status on MRI Predict Survival in Rectal Cancers: Experience from the Indian Subcontinent

To determine the role of MRI as a predictor of circumferential resection margin (CRM) involvement. To study the impact of CRM status on MRI on recurrence and survival, in correlation with pathology. Analysis of a prospective database was performed over a period of 1 year. All patients with adenocarcinoma of rectum were included in the study. The MRI at presentation for all patients irrespective of stage (MRIT), pre-NACTRT MRI (MRI1) for patients with locally advanced tumours, and post-NACTRT MRI (MRI2) of these patients were analysed separately. The status of CRM on MRI was compared to that on histopathology and as a predictor of recurrence and survival. Two hundred twenty-one patients were included with a median follow-up 30 months. Sensitivity, specificity, positive predictive value, negative predictive value (NPV) and accuracy were 50%, 65.46%, 5.63%, 96.95% and 64.85% for MRIT; 50%, 55.32%, 5.97%, 95.12% and 55.03% for MRI1; and 77.78%, 63.29%, 10.77%, 98.04% and 64.07% for MRI2, respectively. On multivariate analysis, pathological positive margin alone predicted a poor overall survival (OS) whereas involved CRM on pathology and MRIT predicted poorer disease-free survival (DFS) and local recurrence. Pre-treatment and post-treatment MRI scans have a moderate sensitivity, specificity and accuracy and a high negative predictive value to predict CRM status on pathology. Pathological CRM status is the only factor to impact OS, DFS and LR on multivariate analysis. CRM status on MRI at presentation (MRIT) does impact DFS and local recurrence but not OS.

Persistent involvement of anterior mesorectal fascia in carcinoma rectum - extended resection of rectum vs total pelvic exenteration: results from a single-centre retrospective study

AIM

Involvement of the anterior mesorectal fascia (iAMRF) after neoadjuvant treatment leads to either resection of the involved organ alone [extended resection of the rectum (ERR)] or total pelvic exenteration (TPE). The purpose of this study was to compare the rate of recurrence and survival of patients undergoing ERR or TPE for iAMRF after neoadjuvant treatment. The outcome of patients who underwent total mesorectal excision after downstaging was also compared.

METHOD

This was a retrospective study of primary rectal cancer patients.

RESULTS

Of 237 patients, 61 (21.5%) patients with nonmetastatic carcinoma rectum had iAMRF at baseline. Ten patients defaulted before completion of neoadjuvant chemoradiotherapy. After neoadjuvant chemoradiotherapy, 22 patients (43.1%) developed systemic metastases, seven patients (13.8%) were downstaged to free anterior mesorectal fascia and underwent total mesorectal excision (anterior resection/abdominoperineal resection) and the remaining 22 patients (43.1%) had persistent iAMRF. Thirteen patients with persistent iAMRF underwent ERR, whereas nine patients underwent TPE. The median duration of hospital stay in the TPE group was 13 days (10-26), whereas it was 7 days (5-21) in the ERR group. A clear circumferential resection margin, R0 resection, was achieved in all patients with TPE and ERR. After a median follow-up of 31.6 months, five patients with TPE (55.6%), four patients with ERR (30.7%) and three patients in the downstaged group (42.9%) developed systemic recurrence. None of the patients with TPE and the downstaged group developed local recurrence, whereas three patients with ERR (23.1%) developed local recurrence. Median disease-free survival was 12.3 months in the TPE group, 18.9 months in the ERR group and 10.6 months in the downstaged group, whereas mean overall survival was 36.2, 32.8 and 27.9 months, respectively.

CONCLUSION

Although there is no significant difference in the overall survival and disease-free survival, ERR is associated with a high risk of local recurrence compared to TPE and the downstaged group.

Mucinous Rectal Adenocarcinoma Is Associated with a Poor Response to Neoadjuvant Chemoradiotherapy: A Systematic Review and Meta-analysis

BACKGROUND

Mucinous adenocarcinoma represents a potentially poor prognostic subgroup of rectal cancer. A consensus on the effect of mucinous cancer on outcomes following neoadjuvant chemoradiotherapy and curative resection for rectal cancer has not been reached.

OBJECTIVE

The aim of the current study is to use meta-analytical techniques to assess the association between mucinous histology and response to neoadjuvant chemoradiotherapy in rectal cancer.

DATA SOURCES

A comprehensive literature search of PubMed, Embase, and The Cochrane Library was performed.

STUDY SELECTION

All studies examining the effect of mucinous histology on chemotherapeutic response in rectal cancer were included.

INTERVENTIONS

No direct interventions were performed.

MAIN OUTCOME MEASURES

Outcomes of mucinous rectal adenocarcinoma were compared with nonmucinous tumors by using random-effects methods to analyze data. Data are presented as ORs with 95% CIs. The main outcomes measured were the rates of pathological complete response, tumor and nodal downstaging, positive resection margin rate, local recurrence, and overall mortality.

RESULTS

Eight comparative series describing outcomes in 1724 patients were identified, 241 had mucinous tumors (14%). Mucinous tumors had a reduced rate of pathological complete response (OR, 0.078; 95% CI, 0.015-0.397; p = 0.002) and tumor downstaging (OR, 0.318; 95% CI, 0.185-0.547; p < 0.001) following neoadjuvant chemoradiotherapy with an increased rate of positive resection margin (OR, 5.018; 95% CI, 3.224-7.810; p < 0.001) and poorer overall survival (OR, 1.526; 95% CI, 1.060-2.198; p = 0.023) following resection. Mucin expression did not significantly affect nodal downstaging (OR, 0.706; 95% CI, 0.295-1.693; p = 0.435) or local recurrence (OR, 1.856; 95% CI, 0.933-3.693; p = 0.078). There was no across-study heterogeneity for any end point.

LIMITATIONS

Most studies were retrospectively designed, and there were variations in patient populations and duration of follow-up.

CONCLUSIONS

Mucinous rectal adenocarcinoma represents a biomarker for poor response to preoperative chemoradiotherapy and is an adverse prognostic indicator.

MRI Local Staging and Restaging in Rectal Cancer

Magnetic resonance imaging (MRI) with rectal protocol modification is a reliable staging modality which is rapidly replacing transrectal ultrasound for staging. The added information delivered by MRI includes wide circumferential radial margin compromise, distant lymph node metastasis in the pelvis, and level of sphincter compromise in the low rectum. As more information becomes available through ongoing studies, MRI may be able to contribute the decision to treat rectal cancer nonoperatively.