Management and imaging of low rectal carcinoma

Evaluation of treatment response by multiparametric MR imaging in locally advanced rectal tumors following neoadjuvant chemotherapy

PURPOSE

To investigate the effectiveness of multiparametric MRI examination in determining tumor response after neoadjuvant chemoradiotherapy (CRT) in locally advanced rectal tumors.

METHODS

46 patients with locally advanced rectal adenocarcinoma were included and were divided into two groups as complete responders and nonresponders based on Mandard score. On MRI, relative T2w signal intensity and ADC values obtained before and after treatment and tumour volumes in dynamic contrast enhanced images (DCI) were used to determine complete response to treatment.

RESULTS

There were no significant differences between mean ADC values obtained by single slice ADC and three circular ROI methods. There were significant differences between two groups in terms of Post-CRT ADC value, ΔADC and %ΔADC obtained by whole tumour volume ADC method (p < 0.05). There were significant differences between Pre-CRT and Post-CRT volume values. ΔV DCI and %ΔV DCI, ΔV ADC and T2w volume values were significantly lower in complete responders (p < 0.05). In multivariate analysis, sensitivity and specificity were calculated as 88.9% and 91.9% (AUC = 0.943) when Post-CRT mean ADC value and Post-CRT DCI volume values were used together, and sensitivity and specificity were calculated as 88.9% and 94.6% (AUC = 0.949) when ΔADC and Post-CRT DCI volume values were used together.

CONCLUSION

Whole tumour volume mean ADC value is the most useful method to determine treatment response. Post-CRT DCI volume measurement stands out as the most useful method in assessing complete response alone. The highest diagnostic values are achieved when the post-CRT DCI volume is combined with the ADC change value of the whole tumor volume.

A multicentre cohort study assessing the utility of routine blood tests as adjuncts to identify complete responders in rectal cancer following neoadjuvant chemoradiotherapy

PURPOSE

Management of rectal cancer with a complete clinical response (cCR) to neoadjuvant chemoradiotherapy (NACRT) is controversial. Some advocate "watch and wait" programmes and organ-preserving surgery. Central to these strategies is the ability to accurately preoperatively distinguish cCR from residual disease (RD). We sought to identify if post-NACRT (preoperative) inflammatory markers act as an adjunct to MRI and endoscopy findings for distinguishing cCR from RD in rectal cancer.

METHODS

Patients from three specialist rectal cancer centres were screened for inclusion (2010-2015). For inclusion, patients were required to have completed NACRT, had a post-NACRT MRI (to assess mrTRG) and proceeded to total mesorectal excision (TME). Endoluminal response was assessed on endoscopy at 6-8 weeks post-NACRT. Pathological response to therapy was calculated using a three-point tumour regression grade system (TRG1-3). Neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), serum albumin (SAL), CEA and CA19-9 levels post-NACRT (preoperatively) were recorded. Variables were compared between those who had RD on post-operative pathology and those with ypCR. Statistical analysis was performed using SPSS (version 21).

RESULTS

Six hundred forty-six patients were screened, of which 422 were suitable for inclusion. A cCR rate of 25.5% (n = 123) was observed. Sixty patients who achieved cCR were excluded from final analysis as they underwent organ-preserving surgery (local excision) leaving 63 ypCR patients compared to 359 with RD. On multivariate analysis, combining cCR on MRI and endoscopy with NLR < 5 demonstrated the greatest odds of ypCR on final histological assessment [OR 6.503 (1.594-11.652]) p < 0.001]. This method had the best diagnostic accuracy (AUC = 0.962 95% CI 0.936-0.987), compared to MRI (AUC = 0.711 95% CI 0.650-0.773) or endoscopy (AUC = 0.857 95% CI 0.811-0.902) alone or used together (AUC = 0.926 95% CI 0.892-0.961).

CONCLUSION

Combining post-NACRT inflammatory markers with restaging MRI and endoscopy findings adds another avenue to aid distinguishing RD from cCR in rectal cancer.

MRI of Rectal Cancer: Tumor Staging, Imaging Techniques, and Management

Rectal cancer is prone to local recurrence and systemic metastasis. However, owing to improvements in TNM staging and treatment, including a more widespread use of rectal MRI and increased radiologist awareness of the key rectal cancer TNM staging features, the mortality rate of rectal cancer has been declining over the past few decades in adults over 50 years of age. Currently, rectal MRI plays a key role in the pre- and posttreatment evaluation of rectal cancer, assisting the multidisciplinary team in tailoring the most appropriate treatment option. The benefits achieved with rectal MRI are strictly dependent on obtaining good-quality images, which is important for the characterization of the main anatomic structures and their relationship with the tumor. In primary staging, rectal MRI helps the radiologist (a) describe the tumor location and morphology, (b) provide its T and N categories, (c) detect the presence of extramural vascular invasion, and (d) identify its relationship with surrounding structures, including the sphincter complex and involvement of the mesorectal fascia. These features help diagnose locally advanced rectal tumors (categories T3c-d, T4, N1, and N2), for which neoadjuvant chemoradiotherapy (CRT) is indicated. In restaging after neoadjuvant CRT, in addition to reassessing the features noted during primary staging, rectal MRI can help in the assessment of treatment response, especially with the emergence of nonsurgical approaches such as "watch and wait." ^©RSNA, 2019.

The use of MR imaging in treatment planning for patients with rectal carcinoma: have you checked the "DISTANCE"?

Rectal cancer is a common and serious disease in the Western hemisphere. Optimal treatment of rectal cancer involves a multidisciplinary approach, with collaboration required between radiologists, oncologists, surgeons, and pathologists to achieve local control and decrease the rate of recurrence. Several studies have been published that show the ability to accurately stage rectal cancer with magnetic resonance (MR) imaging. Moreover, advances in preoperative therapies require accurate preoperative staging with MR imaging to select those patients who may benefit from more intensive treatment, without subjecting those who will not benefit to unnecessary treatment. As we enter an era of individualized patient care, stratified according to the risk of both local and distant failure, imaging takes on the same importance as the tumor type and genetic susceptibility. MR imaging is now an essential tool to enable the oncology team to make appropriate treatment decisions. However, rectal cancer evaluation with MR imaging remains a challenge in the hands of nonexperts. This article describes a mnemonic device, "DISTANCE," to enable a systematic approach to the interpretation of MR images, thereby enabling all the clinically relevant features to be adequately assessed: DIS, for Distance from the Inferior part of the tumor to the transitional Skin; T, for T staging; A, for Anal complex; N, for Nodal staging; C, for Circumferential resection margin; and E, for Extramural vascular invasion.

Imaging of anal carcinoma

OBJECTIVE

The purpose of this article is to review the role of imaging in the management of patients with anal cancer. The relevant anatomy, imaging techniques, and interpretation of images of patients before and after therapy will be discussed.

CONCLUSION

Anal carcinomas are uncommon but increasing in frequency. Radiologists must recognize typical patterns of disease at initial evaluation, posttherapy appearances, and when to suspect residual or recurrent disease to guide clinicians and achieve optimal patient outcome.

MR volumetric measurement of low rectal cancer helps predict tumor response and outcome after combined chemotherapy and radiation therapy

PURPOSE

To retrospectively determine whether magnetic resonance (MR) volumetry of rectal cancer is a reproducible method for predicting disease-free survival (DFS) in patients with locally advanced low or midrectal tumors who undergo combined chemotherapy and radiation therapy (CRT) before total mesorectal excision.

MATERIALS AND METHODS

The institutional review board does not require approval for the use of patient data obtained for an observational retrospective study. Fifty-eight patients were included in the study; 42 patients had low-lying tumors. Two radiologists independently measured tumor volumes before and after CRT with use of semiautomated software. The radiologists were blinded to the clinical information for each patient. The tumor volume reduction ratio, circumferential resection margin, T stage, and occurrence of downstaging were compared with the histopathologic response and DFS. The threshold of tumor volume reduction for predicting DFS was assessed with receiver operating characteristic curve analysis. DFS was estimated with the Kaplan-Meier method and compared between groups with the log-rank test.

RESULTS

The interobserver correlation coefficient between the two radiologists was 0.87 (95% confidence interval [CI]: 0.76, 0.93) for pre-CRT volumetry and 0.81 (95% CI: 0.74, 0.90) for post-CRT volumetry. A tumor volume reduction of at least 70% was significantly associated with good histologic regression (tumor regression grade [TRG], 3 or 4) (P <.0001) compared with a volume reduction rate of less than 70%. DFS was studied in 51 patients. The mean follow-up of survivors at the time of analysis was 52 months ± 20 (standard deviation). Patients with a volume reduction ratio of at least 70% had a higher DFS (P <.0001). Tumor volume reduction was an independent prognostic parameter in multivariate analysis for DFS (P = .003; 95% CI: 0.01, 0.4).

CONCLUSION

The results demonstrate that volumetric measurements are reliable markers of rectal cancer prognosis, enabling the prediction of DFS and TRG. The cutoff of 70% is an easy parameter to use as a surrogate for clinical response to predict both TRG and outcome.

Magnetic resonance imaging (MRI) in rectal cancer: a comprehensive review

Magnetic resonance imaging (MRI) has established itself as the primary method for local staging in patients with rectal cancer. This is due to several factors, most importantly because of the ability to assess the status of circumferential resection margin. There are several newer developments being introduced continuously, such as diffusion-weighted imaging and imaging with 3 T. Assessment of loco-regional lymph nodes has also been investigated extensively using different approaches, but more work needs to be done. Finally, evaluation of tumours during or after preoperative treatment is becoming an everyday reality. All these new aspects prompt a review of the most recent advances and opinions. In this review, a comprehensive overview of the current status of MRI in the loco-regional assessment and management of rectal cancer is presented. The findings on MRI and their accuracy are reviewed based on the most up-to-date evidence. Optimisation of MRI acquisition and relevant regional anatomy are also presented, based on published literature and our own experience.

Magnetic resonance imaging prediction of an involved surgical resection margin in low rectal cancer

PURPOSE

Low rectal cancers (<5 cm from the anal verge), compared with all others, have greater positive resection margin rates, attributed to mesorectal tapering and higher perforation risk. The aim of this study was to assess positive resection margin prediction by using magnetic resonance imaging staging.

METHODS

The following features were analyzed by using preoperative magnetic resonance imaging from 101 consecutive patients with low rectal tumors: tumor location (posterior/anterior) and magnetic resonance stage (Stage 1-2, tumor within the intersphincteric plane; Stage 3-4 tumor extending into the intersphincteric plane). Magnetic resonance imaging tumor regression grade was measured where posttreatment magnetic resonance imaging was available and compared with histopathologic findings.

RESULTS

Seventy of 101 patients had abdominoperineal excisions, and 31 of 101 had low anterior resections. Using logistic regression, positive resection margin odds were higher for magnetic resonance Stages 3 to 4 than Stages 1 to 2 by a factor of 17.7 (P < 0.001), and positive resection margin odds were higher by a factor of 2.8 for anterior vs. posterior tumors (P = 0.026). Magnetic resonance imaging tumor regression grade strongly predicted for positive resection margins; 11 of 15 patients with little treatment response had positive resection margins, compared with 2 of 15 with >50 percent complete treatment response on magnetic resonance imaging (P < 0.001).

CONCLUSION

Significant magnetic resonance imaging positive resection margin predictors are tumor into or beyond the intersphincteric plane and magnetic resonance imaging tumor regression grade.

MRI staging of low rectal cancer

Low rectal tumours, especially those treated by abdominoperineal excision (APE), have a high rate of margin involvement when compared with tumours elsewhere in the rectum. Correct surgical management to minimise this rate of margin involvement is reliant on highly accurate imaging, which can be used to plan the planes of excision. In this article we describe the techniques for accurate magnetic resonance imaging (MRI) assessment and a novel staging system for low rectal tumours. Using this staging system it is possible for the radiologist to demonstrate accurately tumour-free planes for surgical excision of low rectal tumours.

Sites of surgical wasting in the abdominoperineal specimen

BACKGROUND

In the abdominoperineal excision (APE) specimen 'surgical wasting' has been described, where the least amount of tissue covers the rectum. This is associated with high positive margin rates. The aim of this study was to locate the site of surgical wasting, namely the least amount of tissue excised at APE.

METHODS

Distances from the anal verge to the distal and proximal edges of the sphincter, puborectalis and levator muscles were measured in 12 patients using morphological features on magnetic resonance images. Distances from the mucularis propria to the outer surface of the pelvic muscles and the outer edge of the specimen were measured on axial images. The height from the anal verge at which axial measurements of tissue were minimal was determined.

RESULTS

The presence of a surgical waist between 35 and 42 mm above the anal verge, corresponding to the puborectalis, was confirmed. A smaller amount of perirectal tissue was resected at this level than at other heights (P < 0.001).

CONCLUSION

Because less tissue is excised at the puborectalis, careful dissection along the levator plane is necessary, especially if tumour is present. More radical excision of the levators and puborectalis may be of benefit in such patients.

Prognostic factors after preoperative irradiation and surgery for locally advanced rectal cancer

AIMS

The experience of preoperative irradiation in clinically locally advanced rectal cancer for the period 1991-2003 is reported. Prognostic factors for survival and recurrence, and parameters for obtaining a free circumferential margin were evaluated.

METHODS

A prospective cohort study of 204 M0 patients given >45 Gy preoperatively (median age 66 years; 29% women; tumour level <16 cm from the anal verge).

RESULTS

Multivisceral and/or pelvic wall resections were performed in 61% of the patients. R0, R1 and R2 resections were achieved in 74%, 21% and 5%. Five-year survival was 52% for all patients, 60% for R0 resections, 31% for R1 and 0% for R2. The calculated 5-year recurrence rates were 13% for R0 resections and 24% for R1 resections (p<0.035). R-stage, N-stage, age, type of rectal resection and pelvic wall resection remained significant in Cox multivariate analysis for survival. Regarding local recurrence, the following parameters were independent: N-stage, carcinoembryonic antigen (CEA) response and pelvic wall resection. Medium high tumour level and reduced histopathological differentiation are important individual factors that seem to predict increased risk for not obtaining a R0 resection.

CONCLUSIONS

After preoperative irradiation and surgery, about 50% of the patients with locally advanced rectal cancer without overt metastases (M0) can be cured.

Better surgery and better selection for adjuvants--still the key to improving outcomes in rectal cancer

In reviewing the current issues in rectal cancer management the word specialist recurs again and again. The modern hospital requires consultants with special interest in each of the key stages of decision making: Clinical assessment--usually the surgeon MRI. Fine slice individually orientated phased array coil studies with a specially trained radiologist. CT--now routine for metastases Neo-adjuvant therapy. Special interest in the disease in both clinical and medical oncology is essential.

SURGERY

The challenges of the distal pelvis make it increasingly unacceptable for surgeons without a "special interest" to operate on mid and low cancer. Histopathology: The lessons of Professor Quirke have brought the specialised histopathologist out of his laboratory into the cruel role of "surgical auditor"--providing circumferential margin examination plus naked eye, TME quality assessment. This gives us two invaluable measurable short-term goals improving the quality for surgical practice. When a hospital can provide special interest doctors in all these fields and when they co-operate in a constructive manner the modern colorectal MDT can lead the way for the whole field of cancer management. It remains a probability that the use of high definition improved quality video based teaching of surgical technique is the single most effective weapon that we have in our battle against this most challenging of malignanvies.

Preoperative radiotherapy for operable rectal cancer--is a lower dose to a reduced volume acceptable?

AIMS

A retrospective audit was carried out to determine the rate of local recurrence (recurrent tumour within the lesser pelvis or the perineal wound) in 88 rectal cancer patients treated with 20 Gy/four fractions of adjuvant preoperative radiotherapy and curative surgery.

MATERIALS AND METHODS

All patients were followed-up by clinical examination with rigid sigmoidoscopy at 6 monthly intervals if the rectum was intact, and computed tomography of the pelvis at 1, 2 and 5 years after surgery. In total, 171 patients with rectal cancer were identified under the care of one surgeon over a period of 11 years from May 1992 to April 2003. We excluded patients with rectal cancer from preoperative adjuvant radiotherapy if they had evidence at presentation of distant metastases, if they had fixed rectal tumours, were treated by local excision and had previous radiotherapy to the pelvis. On this basis, only 88 were considered for preoperative radiotherapy and curative resection with a median follow-up of 5.16 years.

RESULTS

The 5-year survival by stage was Dukes A 96%, Dukes B 65% and Dukes C 36%. Overall, four patients (of 88) developed a recurrence within the lesser pelvis or the perineal wound, giving a local recurrence of 4.2% at 3 years (from a Kaplan-Meier graph).

CONCLUSIONS

This single-centre audit suggests that a lower dose of radiotherapy to a smaller volume provides an acceptable local recurrence rate that compares very favourably with the well-publicised Swedish and Dutch trials of 25 Gy/five fractions. It was not the intention of this audit to suggest that this dose should be widely adopted. However, given the long-term gastrointestinal morbidity and risk of second malignancies, we advise caution when formulating even more intensive radiotherapy and chemoradiotherapy regimens for rectal cancer.

Magnetic resonance imaging of the low rectum: defining the radiological anatomy

Low rectal cancer provides a particular surgical challenge of local tumour control and sphincter preservation. Histopathological studies have shown that an involved circumferential resection margin (CRM) and depth of extramural invasion are independent markers of poor prognosis and correlate with high local recurrence rates due to residual microscopic disease [1]. Recent data suggests that a CRM at risk of tumour involvement can be reliably seen on the pre-operative magnetic resonance imaging (MRI) scan with good correlation with the histological specimen [2-5]. In published series, low rectal cancers have a higher incidence of involved resection margins, with rates up to 30% for abdomino-perineal excision (APE) vs 10% for low anterior resection (LAR) [6-9]. This has been attributed to narrow surgical planes deep within the pelvis as the mesorectum becomes narrowed and tapered, forming a bare muscle tube at the level of the anal sphincter complex. The challenge for the surgeon is to undertake careful removal of a cylinder of tissue beyond the rectal wall without perforating the tumour. An overall local recurrence rate of 10% after APE for all stages of rectal cancer has been reported and this low rate was attributed to the surgical technique that included a wide peri-anal dissection and lateral division of the levator ani. The abdominal dissection was stopped above the tumour, taking care to avoid separation of the tumour from the levator ani to reduce the risk of inadvertent tumour cell spillage [8]. Therefore, rates of involved surgical margins from APE specimens may be reduced when a cuff of levators is taken compared with standard resection. In this review, we will discuss how MRI of the low rectum can aid in the staging and optimization of the best treatment strategy for low rectal cancer.

Pathological assessment of rectal carcinoma after preoperative therapy

Increasingly neoadjuvant therapy is being used to improve outcomes in patients with rectal carcinoma in which the circumferential resection margins are considered to be at risk for involvement if primary surgery were to be undertaken. Assessment of the response to this approach relies on radiological examination, particularly magnetic resonance imaging (MRI) studies. Following definitive surgery, careful histological examination allows full assessment of the tumour response to these preoperative approaches. Histological examination requires careful fixation, examination of the entire area occupied by the tumour prior to down-staging and careful lymph node harvesting. Adequate fixation helps in these endeavours and the lymph node harvest appears to be unaffected by neoadjuvant chemo- or radiotherapy. Correlation between preoperative assessment of response by MRI and the subsequent histological assessment is close, but the presence of isolated residual neoplastic glands in a post-treatment fibrotic stroma is impossible to detect prior to resection. The clinical significance of these microscopic foci remains uncertain, particularly in view of the prolonged tumour doubling time associated with colorectal adenocarcinoma. The preoperative discussion with the patient requires a synthesis of their own scan results and the experience of detailed clinico-pathological studies. While MRI frequently predicts the presence or absence of residual tumour the possibility of under-staging remains and this is of crucial importance if a 'watch and wait' policy is to be adopted following apparent complete clinical and radiological remission. The significance of potential residual microscopic disease in patients with apparent radiological complete remission needs further investigation but may need to be interpreted in individual patients in the context of overall life-expectancy.

Adjuvant radiotherapy is associated with increased sexual dysfunction in male patients undergoing resection for rectal cancer: a predictive model

OBJECTIVES

The objectives of this study were to evaluate the effect of radiotherapy (RT) on sexual function in patients undergoing oncologic resection for rectal cancer, and to develop a mathematical model for quantifying the risk of sexual dysfunction through time for this group of patients.

METHODS

Data were prospectively collected on patients undergoing proctosigmoidectomy (group 1: n = 101) or adjuvant radiotherapy (40-50 Gy) and resection (group 2: n = 100) for rectal cancer at a tertiary referral center between December 1998 and July 2004. Study end points were recorded at 7 time intervals (preoperatively, 4 months, 8 months, 1 year, 2 years, 3 years, and 4 years after surgery) and included: 1) ability to have an erection, 2) maintain an erection, 3) attain orgasm, 4) dry orgasm, and 5) whether they were sexually active. Multilevel logistic regression analysis for repeated measures was used to identify factors associated with the sexual dysfunction. A predictive model was developed and internally validated by comparing observed and model-predicted outcomes.

RESULTS

Radiotherapy had an adverse effect on the ability to get an erection, maintain an erection, attain orgasm, and being sexually active in comparison with patients undergoing surgery alone (7.4%, 12.6%, 16.2%, and 13.7% reduction 8 months after surgery respectively; P < 0.05). The effect of sexual dysfunction deteriorated with age (odds ratio for erectile function, 0.40 per 10-year increase in age; 95% confidence interval, 0.29-0.49; P < 0.001). A significant variability in sexual function was present among the 7 time points with a maximal deterioration occurring at 8 months after surgery with subsequent slow but not complete recovery (P < 0.001). The predictive model showed adequate discrimination on 4 of the 5 domains of sexual dysfunction (area under the receiver operating characteristic curve >0.70).

CONCLUSIONS

Radiotherapy has an adverse effect on sexual function, the effect being maximal at 8 months after surgery. The risk of sexual dysfunction can be quantified preoperatively using the proposed index and can assist patients in making better informed choices on the type of treatment they receive.