Nonoperative management of rectal cancer with complete clinical response after neoadjuvant therapy. Ann Surg. 2012;256:965-972. [PMID: 23154394 DOI: 10.1097/sla.0b013e3182759f1c]

Avoiding radical surgery improves early survival in elderly patients with rectal cancer, demonstrating complete clinical response after neoadjuvant therapy: results of a decision-analytic model

BACKGROUND

In elderly and comorbid patients with rectal cancer, radical surgery is associated with significant perioperative mortality. Data suggest that a watch-and-wait approach where a complete clinical response is obtained after neoadjuvant chemoradiotherapy might be oncologically safe.

OBJECTIVE

This study aimed to determine whether patient age and comorbidity should influence surgeon and patient decision making where a complete clinical response is obtained.

DESIGN

Decision-analytic modeling consisting of a decision tree and Markov chain simulation was used. Modeled outcome parameters were elicited both from comprehensive literature review and from a national patient outcomes database.

SETTINGS

Outcomes for 3 patient cohorts treated with neoadjuvant therapy were modeled after either surgery or watch and wait.

PATIENTS

Patients included 60-year-old and 80-year-old men with mild comorbidities (Charlson score <3) and 80-year-old men with significant comorbidities (Charlson score >3).

MAIN OUTCOME MEASURES

Absolute survival, disease-free survival, and quality-adjusted life years were measured.

RESULTS

The model found that absolute survival was similar in 60-year-old patients but was significantly improved in fit and comorbid 80-year-old patients at 1 year after treatment where watch and wait was implemented instead of radical surgery, with a survival advantage of 10.1% (95% CI, 7.9-12.6) and 13.5% (95% CI, 10.2-16.9). At all of the other time points, absolute survival was equivalent for both techniques. There were no short- or long-term differences among any patient groups managed either by radical surgery or watch and wait in terms of either disease-free survival or quality-adjusted life years.

LIMITATIONS

Oncologic data for the watch-and-wait approach used for this study is derived from only a small number of studies pertaining to a highly selected group of patients. The 90-day postoperative mortality rate derived from the United Kingdom population-based study might be lower in other countries or individual institutions.

CONCLUSIONS

This study suggests competing effects of oncologic and surgical risk when using watch-and-wait management and that elderly and comorbid patients have the most to gain from this approach.

The role of tissue diagnosis prior to neoadjuvant chemoradiotherapy for locally advanced rectal cancer

AIM

Neoadjuvant chemoradiotherapy is the standard of care for locally advanced rectal cancer, with diagnostic work-up routinely including a biopsy confirming invasive carcinoma. For the occasional patient where initial biopsies reveal only dysplasia, or even normal epithelium, repeat biopsy is currently advised, but this may delay therapy and repeat biopsy has potential adverse effects. The study aimed to determine, in the setting of clinical findings and imaging demonstrating locally advanced rectal cancer, whether the absence of a tissue diagnosis prior to commencing chemoradiation compromises patient outcome.

METHOD

A review was conducted of our database, including comprehensive treatment and outcome details, in which consecutive patients with colorectal cancer have been enrolled since 1997 at a single institution. All records for patients who received neoadjuvant chemoradiotherapy for locally advanced rectal cancer were reviewed to identify patients for whom treatment was initiated before a tissue diagnosis was obtained, and to assess any consequences of this.

RESULTS

Of 254 patients who had received neoadjuvant treatment for rectal cancer, 16 (6.3%) were found to have had neoadjuvant therapy without a tissue diagnosis of invasive cancer. Compared with cases where a tissue diagnosis had been obtained, median age (59 vs 63 years, P = 0.497), sex (75% vs 71.3% male, P = 0.955) and tumour location (56.3% vs 73.5% < 8 cm, P = 0.230) were similar. Of these, 14 (87.5%) had adenocarcinoma identified on histopathology review of the surgical specimen. Three patients were considered to have had complete pathological responses with mucin lakes within the muscularis propria (n = 2) or lymph nodes (n = 1) or fibrosis (n = 3). One of these had no mucin evident and only fibrosis; thus final pathological proof of invasive cancer was present in 15 (93.5%) patients. There were no local recurrences, but three of the 16 (18.8%) cases developed distant recurrence.

CONCLUSION

For the small number of cases without a confirmatory tissue diagnosis before chemoradiation, no adverse consequences were identified. In particular the initial diagnosis was confirmed in 15 out of 16 cases following pathological examination of the operative specimen. We would suggest that, where clinical and radiological features support a diagnosis of locally advanced rectal cancer, proceeding directly to neoadjuvant chemoradiotherapy in the absence of a biopsy demonstrating invasive cancer may not be unreasonable, particularly where repeat biopsy would delay the commencement of treatment.

Impact of radiotherapy boost on pathological complete response in patients with locally advanced rectal cancer: a systematic review and meta-analysis

PURPOSE

We conducted a systematic review and meta-analysis to quantify the pathological complete response (pCR) rate after preoperative (chemo)radiation with doses of ⩾60Gy in patients with locally advanced rectal cancer. Complete response is relevant since this could select a proportion of patients for which organ-preserving strategies might be possible. Furthermore, we investigated correlations between EQD2 dose and pCR-rate, toxicity or resectability, and additionally between pCR-rate and chemotherapy, boost-approach or surgical-interval.

METHODS AND MATERIALS

PubMed, EMBASE and Cochrane libraries were searched with the terms 'radiotherapy', 'boost' and 'rectal cancer' and synonym terms. Studies delivering a preoperative dose of ⩾60 Gy were eligible for inclusion. Original English full texts that allowed intention-to-treat pCR-rate calculation were included. Study variables, including pCR, acute grade ⩾3 toxicity and resectability-rate, were extracted by two authors independently. Eligibility for meta-analysis was assessed by critical appraisal. Heterogeneity and pooled estimates were calculated for all three outcomes. Pearson correlation coefficients were calculated between the variables mentioned earlier.

RESULTS

The search identified 3377 original articles, of which 18 met our inclusion criteria (1106 patients). Fourteen studies were included for meta-analysis (487 patients treated with ⩾60 Gy). pCR-rate ranged between 0.0% and 44.4%. Toxicity ranged between 1.3% and 43.8% and resectability-rate between 34.0% and 100%. Pooled pCR-rate was 20.4% (95% CI 16.8-24.5%), with low heterogeneity (I2 0.0%, 95% CI 0.00-84.0%). Pooled acute grade ⩾3 toxicity was 10.3% (95% CI 5.4-18.6%) and pooled resectability-rate was 89.5% (95% CI 78.2-95.3%).

CONCLUSION

Dose escalation above 60 Gy for locally advanced rectal cancer results in high pCR-rates and acceptable early toxicity. This observation needs to be further investigated within larger randomized controlled phase 3 trials in the future.

Multidisciplinary treatment of rectal cancer in 2014: where are we going?

In the present review we discuss the recent developments and future directions in the multimodal treatment of locally advanced rectal cancer, with respect to staging and re-staging modalities, to the current role of neoadjuvant chemo-radiation and to the conservative and more limited surgical approaches based on tumour response after neoadjuvant combined therapy. When initial tumor staging is considered a high accuracy has been reported for T pre-treatment staging, while preoperative lymph node mapping is still suboptimal. With respect to tumour re-staging, all the current available modalities still present a limited accuracy, in particular in defining a complete response. The role of short vs long-course radiotherapy regimens as well as the optimal time of surgery are still unclear and under investigation by means of ongoing randomized trials. Observational management or local excision following tumour complete response are promising alternatives to total mesorectal excision, but need further evaluation, and their use outside of a clinical trial is not recommended. The preoperative selection of patients who will benefit from neoadjuvant radiotherapy or not, as well as the proper identification of a clinical complete tumour response after combined treatment modalities,will influence the future directions in the treatment of locally advanced rectal cancer.

MR imaging for rectal cancer: the role in staging the primary and response to neoadjuvant therapy

Pre-operative staging is an essential aspect of modern rectal cancer management and radiological assessment is central to this process. An ideal radiological assessment should provide sufficient information to reliably guide pre-operative decision-making. Technical advances allow high-resolution imaging to not only provide prognostic information but to define the anatomy, helping the surgeon to anticipate potential pitfalls during the operation. The main imaging modality for local staging of rectal cancer is Magnetic Resonance Imaging (MRI), as it defines the tumour and relevant anatomy providing the most detail on the important prognostic factors that influence treatment choice. In addition, there is an emerging role for MRI in the assessment of the response to neoadjuvant therapy. This article is an evidence-based review of rectal cancer staging focusing on post-treatment assessment of response using MRI. The discussion extends into the implications for reliably assessing response and how this may influence future rectal cancer management.

Genotypic characteristics of resistant tumors to pre-operative ionizing radiation in rectal cancer

Due to a wide range of clinical response in patients undergoing neo-adjuvant chemoradiation for rectal cancer it is essential to understand molecular factors that lead to the broad response observed in patients receiving the same form of treatment. Despite extensive research in this field, the exact mechanisms still remain elusive. Data raging from DNA-repair to specific molecules leading to cell survival as well as resistance to apoptosis have been investigated. Individually, or in combination, there is no single pathway that has become clinically applicable to date. In the following review, we describe the current status of various pathways that might lead to resistance to the therapeutic applications of ionizing radiation in rectal cancer.

Outcomes in non-metastatic colorectal cancer

The measurement of outcomes in non-metastatic colon and rectal cancer patients is a multi-dimensional endeavor involving prediction tools, standard of care, and best treatment guidelines. Socioeconomic, demographic, and racial impacts on outcome must be carefully considered. Consideration must also be given to measures of cost, quality, and healthcare delivery in response to initiatives meant to optimize patient health while maintaining quality of life.

Future directions in surgery for colorectal cancer: the evolving role of transanal endoscopic surgery

SUMMARY 

The morbidity associated with radical surgery for rectal cancer has launched a revolution in increasingly less-invasive methods of resection, including a recent resurgence in transanal endoscopic surgical approaches. The next evolution in transanal surgery for rectal cancer is natural orifice translumenal endoscopic surgery (NOTES). To date, 14 series of transanal NOTES total mesorectal excision (TME) for rectal cancer have been published (n = 76). Overall, the intraoperative and postoperative complication rates of 8 and 28%, respectively, compare favorably to those expected from laparoscopic and open TME. Short-term follow-up after NOTES TME has yielded no cancer recurrence in average-risk patients. High-risk patients have cancer recurrence rates similar to those after laparoscopic TME. Overall, these early data support transanal NOTES TME as a safe and viable alternative to conventional TME. Advances in instrumentation, surgical expertise and neoadjuvant treatment may expand current indications for NOTES even further.

Chromosomal instability portends superior response of rectal adenocarcinoma to chemoradiation therapy

BACKGROUND

Persistent chromosome segregation errors represent a conspicuous feature of human neoplasms. It is widely accepted that this chromosomal instability is associated with poor prognosis; however, its effect on therapeutic response is a matter of conjecture.

METHODS

Here, the role of chromosome segregation errors in the response of patients with rectal adenocarcinoma to chemoradiation therapy (CRT) was examined. Pretreatment samples from 62 patients were surveyed for evidence of chromosome mis-segregation and mis-segregation frequency was correlated to the pathological response to CRT as determined by the tumor regression grade after surgical resection of irradiated tumors.

RESULTS

Surprisingly, it was found that errors in chromosome segregation predicted enhanced pathological response of rectal adenocarcinoma to CRT (odds ratio, 3.9; P = .02). Furthermore, tumor response inversely correlated with the frequency of cells that exhibited segregation errors during anaphase (correlation coefficient, 0.94; P < .05). Strikingly, elevated chromosome mis-segregation combined with decreased levels of the DNA damage repair protein Mre11 portended a markedly enhanced response (odds ratio, 54.0; P = .008).

CONCLUSIONS

The results of the current study demonstrate that chromosomal instability is a favorable predictor of response to CRT in patients with locally invasive rectal adenocarcinoma. Therefore, the authors propose that downstream structural damage to chromosomes resulting from segregation errors potentiates the effect of DNA-damaging therapies and synergizes with deficiencies in the DNA repair machinery. This work identifies a novel mechanistic marker that foretells treatment response to CRT and suggests that concomitant targeting of whole-chromosome segregation and DNA repair may constitute an effective therapeutic strategy.

Clinical criteria underestimate complete pathological response in rectal cancer treated with neoadjuvant chemoradiotherapy

BACKGROUND

Published criteria define specific mucosal features of clinical complete response for rectal cancer after neoadjuvant chemoradiotherapy.

OBJECTIVE

The aim of this study was to determine the performance of these criteria to identify a pathological complete response.

DESIGN

Histopathology reports were retrieved for consecutive rectal cancers treated with neoadjuvant therapy followed by proctectomy. The mucosal appearance of residual disease was compared with the final pathological stage.

SETTING

This study was conducted at a single-institution, tertiary referral center.

PATIENTS

The study included 238 patients.

INTERVENTIONS

All patients underwent neoadjuvant chemoradiation followed by proctectomy between 1997 and 2007.

MAIN OUTCOME MEASURES

Gross mucosal appearance was compared with the final pathological stage.

RESULTS

Following neoadjuvant chemoradiation, 61 of 238 (25%) patients were downstaged to ypT0. Forty-five of these 61 patients (74%) had a residual mucosal abnormality that precluded assignment of a complete response. Of these, 40 had residual ulcers (up to 10 mm in depth) and 5 had exophytic lesions. The remaining 16 patients with pathological complete response fulfilled criteria for clinical complete response and had either no visible abnormality or a scar. Although mucosal complete clinical response was statistically associated with ypT0 status (p < 0.0001), 6 of 22 (27%) patients with mucosal complete clinical response still had residual disease. Smaller size of residual mucosal abnormality was also associated with ypT0 status (p = 0.002).

LIMITATIONS

This is a retrospective study and preoperative clinical assessment of response is not recorded for comparison to resected specimens.

CONCLUSIONS

The majority of patients attaining ypT0 status do not display mucosal features of complete response. When present, a mucosal complete response is statistically associated with ypT0 status, but is poorly sensitive. If rectal conservation after chemoradiation is to be pursued, alternative means of restaging are required to maximize the number who might benefit from this approach.

Restaging of locally advanced rectal cancer with magnetic resonance imaging and endoluminal ultrasound after preoperative chemoradiotherapy: a systemic review and meta-analysis

BACKGROUND

Magnetic resonance imaging and endoluminal ultrasound play an important role in the restaging of locally advanced rectal cancer after preoperative chemoradiotherapy, yet their diagnostic accuracy is still controversial.

OBJECTIVE

Meta-analysis was performed to estimate the diagnostic performance of MRI and endoluminal ultrasound.

DATA SOURCES

Electronic databases from 1996 to March 2012 were searched.

STUDY SELECTION AND INTERVENTIONS

Either MRI or endoluminal ultrasound was used to restage rectal cancer after chemoradiotherapy or radiation.

MAIN OUTCOME MEASURES

T category, lymph node, and circumferential resection involvement were measured.

RESULTS

The sensitivity estimate for rectal cancer diagnosis (T0) by endoluminal ultrasound (37.0%; 95% CI, 24.0%-52.1%) was higher (p = 0.04) than the sensitivity estimate for MRI (15.3%; 95% CI, 6.5%-32.0%). For T3-4 category, sensitivity estimates of MRI and endoluminal ultrasound were comparable, 82.1% and 87.6%, whereas specificity estimates were poor (53.5% and 66.4%). For lymph node involvement, there was no significant difference between the sensitivity estimates for MRI (61.8%) and endoluminal ultrasound (49.8%). Specificity estimates for MRI and endoluminal ultrasound were 72.0% and 78.7%. For circumferential resection margin involvement, MRI sensitivity and specificity were 85.4% and 80.0%.

LIMITATIONS

To identify the heterogeneity, metaregression was performed on covariates. However, few of the covariates were identified to be statistically significant because of the lack of adequate original data.

CONCLUSION

Accurate restaging of locally advanced rectal cancer by MRI and endoluminal ultrasound is still a challenge. Identifying T0 rectal cancer by imaging is not reliable. Before performing surgery, restaging is important, but some of the T0-2 patients are likely overestimated as T3-4. Both modalities for lymph node involvement are not very good. Magnetic resonance imaging may be a good method to reassess circumferential resection margin.

Paradigm-shifting new evidence for treatment of rectal cancer

BACKGROUND

Treatment of rectal cancer has dramatically evolved during the last three decades shifting toward a tailored approach based on preoperative staging and response to neoadjuvant combined modality therapy (CMT).

METHODS

A literature search was performed using PubMed/Medline electronic databases.

RESULTS

Selected patients with T1 N0 rectal cancer are best treated with local excision by transanal endoscopic microsurgery (TEM). Satisfactory results have been reported after CMT and TEM for the treatment of highly selected T2 N0 rectal cancers. CMT followed by rectal resection and total mesorectal excision is considered the standard of care for the treatment of locally advanced rectal cancer. However, a subset of stage II and III patients may not require neoadjuvant radiation treatment. Finally, there are mounting data supporting a "watch and wait" approach or local excision in patients with complete clinical response after neoadjuvant CMT.

CONCLUSIONS

Current evidence shows that selected T1 N0 rectal cancers can be managed by TEM alone, while locally advanced cancers should be treated by CMT followed by radical surgery. Studies are underway to identify patients that do not benefit from neoadjuvant radiation therapy. A non-operative approach in case of complete clinical response must be validated by large prospective studies.

Neoadjuvant therapy followed by local excision and two-stage total mesorectal excision: a new strategy for sphincter preservation in locally advanced ultra-low rectal cancer

BACKGROUND

With the increased usage of neoadjuvant chemoradiotherapy, improved surgical technique and stapling devices, sphincter-preserving resection has become more frequent for patients with rectal cancer. However, as for locally advanced ultra-low rectal cancer, sphincter-preservation is still facing an enormous challenge.

OBJECTIVE

To introduce an NLT strategy of sphincter-preservation-neoadjuvant therapy (NT) followed by local excision (LE) and two-stage total mesorectal excision (TME)-into the treatment of locally advanced ultra-low rectal cancer (lesions with anal sphincter invasion).

METHODS

From October 2010 to October 2011, nine patients with locally advanced rectal cancer located less than 3 cm from the anal verge were treated by the NLT strategy. All patients had shown good clinical response to NT. The LE procedure was carried transanally 6-8 weeks after completion of the NT. TME was performed to dissect mesorectal lymph nodes 4-6 weeks after LE.

RESULTS

Of the nine patients, the lesion was assessed as T2 in two, T3 in five, and T4 in two before NT, and lymph node metastasis was detected in five patients. The median distance from the tumor to the anal verge was 2.5 cm (range: 1-3 cm). The median follow-up was 27 months (range: 24-34 months). No distant metastasis was detected. Only one patient (11.1%) developed local recurrence at 12 months post-operatively and then underwent abdomino-perineal resection. The remaining eight patients had preserved long-term continence and the median Wexner score at two years post-operation was 4 (range: 2-6).

CONCLUSION

The new NLT strategy can achieve sphincter-preservation in some patients with ultra-low rectal cancer, with favorable oncological outcome and preservation of normal anal sphincter function.

Current approaches and challenges for monitoring treatment response in colon and rectal cancer

Introduction: With the advent of multidisciplinary and multimodality approaches to the management of colorectal cancer patients, there is an increasing need to define how we monitor response to novel therapies in these patients. Several factors ranging from the type of therapy used to the intrinsic biology of the tumor play a role in tumor response. All of these can aid in determining the ideal course of treatment, and may fluctuate over time, pending down-staging or progression of disease. Therefore, monitoring how disease responds to therapy requires standardization in order to ultimately optimize patient outcomes. Unfortunately, how best to do this remains a topic of debate among oncologists, pathologists, and colorectal surgeons. There may not be one single best approach. The goal of the present article is to shed some light on current approaches and challenges to monitoring treatment response for colorectal cancer.

Methods: A literature search was conducted utilizing PubMed and the OVID library. Key-word combinations included colorectal cancer metastases, neoadjuvant therapy, rectal cancer, imaging modalities, CEA, down-staging, tumor response, and biomarkers. Directed searches of the embedded references from the primary articles were also performed in selected circumstances.

Results: Pathologic examination of the post-treatment surgical specimen is the gold standard for monitoring response to therapy. Endoscopy is useful for evaluating local recurrence, but not in assessing tumor response outside of the limited information gained by direct examination of intra-lumenal lesions. Imaging is used to monitor tumors throughout the body for response, with CT, PET, and MRI employed in different circumstances. Overall, each has been validated in the monitoring of patients with colorectal cancer and residual tumors.

Conclusion: Although there is no imaging or serum test to precisely correlate with a tumor's response to chemo- or radiation therapy, these modalities, when used in combination, can aid in allowing clinicians to adjust medical therapy, pursue operative intervention, or (in select cases) identify complete responders. Improvements are needed, however, as advances across multiple modalities could allow appropriate selection of patients for a close surveillance regimen in the absence of operative intervention.

A Predictive Genetic Signature for Response to Fluoropyrimidine-Based Neoadjuvant Chemoradiation in Clinical Stage II and III Rectal Cancer

PURPOSE

Pre-operative chemoradiation (CRT) is currently the standard of care for patients with clinical stage II and III rectal cancer but only about 45% of patients achieve tumor downstaging and <20% of patients achieve a pathologic complete response. Better methods to stratify patients according to potential neoadjuvant treatment response are needed. We used microarray analysis to identify a genetic signature that correlates with a pathological complete response (pCR) to neoadjuvant CRT. We performed a gene network analysis to identify potential signaling pathways involved in determining response to neoadjuvant treatment.

PATIENTS AND METHODS

We identified 31 T3-4 N0-1 rectal cancer patients who were treated with neoadjuvant fluorouracil-based CRT. Eight patients were identified to have achieved a pCR to treatment while 23 patients did not. mRNA expression was analyzed using cDNA microarrays. The correlation between mRNA expression and pCR from pre-treatment tumor biopsies was determined. Gene network analysis was performed for the genes represented by the predictive signature.

RESULTS

A genetic signature represented by expression levels of the three genes EHBP1, STAT1, and GAPDH was found to correlate with a pCR to neoadjuvant treatment. The difference in expression levels between patients who achieved a pCR and those who did not was greatest for EHBP1. Gene network analysis showed that the three genes can be connected by the gene ubiquitin C (UBC).

CONCLUSION

This study identifies a 3-gene signature expressed in pre-treatment tumor biopsies that correlates with a pCR to neoadjuvant CRT in patients with clinical stage II and III rectal cancer. These three genes can be connected by the gene UBC, suggesting that ubiquitination is a molecular mechanism involved in determining response to treatment. Validating this genetic signature in a larger number of patients is proposed.

Role of p53, Bax, p21, and DNA-PKcs in radiation sensitivity of HCT-116 cells and xenografts

BACKGROUND

Molecular factors that dictate tumor response to ionizing radiation in rectal cancer are not well described.

METHODS

We investigated the contribution of p53, p21, Bax, and DNA-PKcs in response to ionizing radiation in an isogeneic colorectal cancer system in vitro and in vivo.

RESULTS

HCT-116 DNA-PKcs(-/-) cells and xenografts were radiosensitive compared with wild-type (WT) HCT-116 cells. HCT-116 p53(-/-) cells and tumor xenografts displayed a radioresistant phenotype. Separately, p21 or Bax deficiency was associated with a radiosensitive phenotype in vitro and in vivo. In vivo, Bax deficiency led to increased tumor necrosis and decreased microvessel density. In vitro, HCT-116 Bax(-/-) cells had decreased levels of vascular endothelial growth factor. HCT-116 WT cells had a more radioresistant phenotype after pancaspase inhibition, but pancaspase inhibition did not alter radiosensitivity in HCT-116 Bax(-/-) cells subjected to ionizing radiation. There was no difference in cell growth in HCT-116 WT cells subjected to transient apoptosis-inducing factor (AIF) inhibition; however, HCT-116 Bax(-/-) cells treated with AIF siRNA followed by ionizing radiation had a significant survival advantage compared with control-treated cells, implicating AIF in the radiosensitivity of Bax(-/-) cells.

CONCLUSION

These data might be used along with other markers to predict response to radiation in patients with rectal cancer.

Current options in chemoradiotherapy for rectal cancer

SUMMARY The management of rectal adenocarcinoma and the role of radiation in the adjuvant and neoadjuvant setting is evolving. Randomized clinical trials established the role of neoadjuvant chemoradiation (CRT), primarily in patients with T3/T4 and/or node-positive tumor presentations. Clinical trials comparing short-course radiotherapy with long-course CRT have been undertaken, and data supporting treatment with definitive CRT-reserving surgery for salvage is emerging. Clinical research to enhance the efficacy of the 5-fluorouracil-based CRT platform is being investigated, incorporating a variety of chemotherapeutics and targeted agents.

Future directions in combined modality therapy for rectal cancer: reevaluating the role of total mesorectal excision after chemoradiotherapy

Most patients who develop rectal cancer present with locoregionally advanced (T3 or node-positive) disease. The standard management of locoregionally advanced rectal cancer is neoadjuvant concurrent chemoradiotherapy (nCRT), followed by radical resection (low-anterior resection or abdominoperineal resection with total mesorectal excision). Approximately 15% of patients can have a pathologic complete response (pCR) at the time of surgery, indicating that some patients can have no detectable residual disease after nCRT. The actual benefit of surgery in this group of patients is unclear. It is possible that omission of surgery in these patients, termed selective nonoperative management, can limit the toxicities associated with standard, multimodal combined modality therapy without compromising disease control. In this review, we discuss the clinical experiences to date using selective nonoperative management and various attempts at escalation of nCRT to improve the number of patients who have a pCR. We also explore several clinical, laboratory, imaging, histopathologic, and genetic biomarkers that have been tested as tools to predict which patients are most likely to have a pCR after nCRT.

Non-operative management for locally advanced rectal cancer: critical review and future perspective

SUMMARY Over the last few decades we have observed important advances in diagnostic imaging, surgery, pathology and multimodal treatments for rectal cancer, as well as increased efforts to reduce treatment-related toxicities and preserve quality of life for curatively treated patients. Neoadjuvant short-course radiotherapy and long-course chemoradiotherapy followed by total mesorectal excision remain widely accepted as the standard of care for patients with locally advanced rectal cancer. However, a carefully selected group of patients achieving a complete response to neoadjuvant chemoradiotherapy may be spared the effects of surgery and achieve satisfactory oncologic outcomes with a ‘wait-and-see’ strategy. Although supported by the results of previous studies, this intriguing paradigm shift needs prospective evaluation within a clinical trial setting and a more accurate prediction and assessment of response by means of tumor biomarkers and diagnostic imaging.

Diffusion weighted MRI: overview and implications for rectal cancer management

Diffusion weighted imaging (DWI) is an MRI technique that quantifies the movement of water molecules at a cellular level. As the diffusion properties of water vary in areas of necrosis, high cellularity, inflammation and fibrosis, this technique is inherently sensitive to different pathologies. Having become a well-established adjunct to standard sequences during neurological MRI, technological advances have enabled extrapolation to abdominopelvic imaging, including staging of rectal cancer. Scan acquisitions can be performed rapidly using widely available equipment and consequently there has been rapid dissemination into routine practice. However, while DWI shows promise for detecting, staging and monitoring rectal cancer response to therapy, the evidence base remains scant with no current consensus for technical protocols, interpretation or integration into rectal cancer management. Moreover, those studies available to date have a small sample size and few observers, and their results may not be generalizable to daily practice. This article outlines the physical principles of DWI, reviews the literature and suggests avenues for future research into this important technical development.