Watch and wait policy after preoperative radiotherapy for rectal cancer; management of residual lesions that appear clinically benign. Eur J Surg Oncol. 2016;42:288-296. [PMID: 26506863 DOI: 10.1016/j.ejso.2015.09.022]

Endoscopic resection of residual rectal neoplasia after definitive chemoradiotherapy for rectal cancer

The conventional approach to treating locally advanced rectal cancer, commonly defined as cT3 or cT4 primary tumors or with nodal metastases, involves chemoradiation (CRT) followed by surgical resection. There is a growing recognition of the potential for nonsurgical management following CRT or total neoadjuvant therapy (TNT), which allows for organ preservation. "Watch and wait" strategy may be considered if complete clinical response is achieved. In cases when adenoma or superficial cancer is present, a novel approach known as "salvage endoscopic resection of the residual disease" is emerging as a viable nonsurgical option for carefully selected patients. This review discusses available evidence and future potential for endoscopic management of residual neoplasia after oncological treatment of rectal cancer.

The implications from the interplay of neoadjuvant chemoradiotherapy and the immune microenvironment in rectal cancer

Neoadjuvant chemoradiotherapy (nCRT) is recommended for the treatment of locally advanced rectal cancer. Even though the combination of nCRT and immune checkpoint inhibitors (ICIs) has received much attention, the specific combination modes and dose fractions in radiotherapy (RT) are still indistinct. This review focuses on the immunological mechanism involved in nCRT, the clinical efficacy, the immunological effect of different combined strategies, concurrent or sequential nCRT plus ICIs, long-course RT and short-course RT. This review discusses the impact of nCRT on tumor immunity and summarizes the availability of different dose fractions in RT and distinct combined strategies, aiming at providing clues for optimal neoadjuvant therapy options that maximize efficacy and minimize side effects.

Role of Local Excision for Suspected Regrowth in a Watch and Wait Strategy for Rectal Cancer

Rectal cancer patients with a clinical complete response to neoadjuvant (chemo)radiation are eligible for Watch and Wait (W&W). For local regrowth, total mesorectal excision (TME) is considered the standard of care. This study evaluated local excision (LE) for suspected local regrowth. From 591 patients prospectively entered into a national W&W registry, 77 patients with LE for regrowth were included. Outcomes analyzed included histopathologic findings, locoregional recurrence, long-term organ preservation, and colostomy-free and overall survival. In total, 27/77 patients underwent early LE (<6 months after neoadjuvant radiotherapy) and 50/77 underwent late LE (≥6 months). Median follow-up was 53 (39−69) months. In 28/77 patients the LE specimen was histopathologically classified as ypT0 (including 9 adenomas); 11/77 were ypT1, and 38/77 were ypT2−3. After LE, 13/77 patients with ypT2−3 and/or irradical resection underwent completion TME. Subsequently, 14/64 patients without completion TME developed locoregional recurrence, and were successfully treated with salvage TME. Another 8/77 patients developed distant metastases. At 5 years, overall organ preservation was 63%, colostomy-free survival was 68%, and overall survival was 96%. There were no differences in outcomes between early or late LE. In W&W for rectal cancer, LE can be considered as an alternative to TME for suspected regrowth in selected patients who wish to preserve their rectum or avoid colostomy in distal rectal cancer.

Rapid Initiation of Neoadjuvant Chemoradiotherapy After Diagnosis is Associated With Improved Pathologic Response in Locally Advanced Rectal Cancer

INTRODUCTION

In rectal cancer, neoadjuvant chemoradiation (NCRT) is preferred because of toxicity profile, improved resectability and sphincter preservation, although with no impact on overall survival. Pathologic complete response (pCR) to NCRT has been linked with longer disease-free survival (DFS). The study purpose was to evaluate an association between clinical factors and treatment schedule with tumor response and treatment outcome, among patients with locally advanced rectal cancer.

PATIENTS AND METHODS

In this single-center retrospective study, conducted over 9 years (2011 to 2020), patients with stage II to III rectal cancer who had received NCRT were enrolled. The standard radiotherapy was 45 Gy to the pelvis, with a simultaneous integrated 50 Gy boost to the primary tumor. Continuous 5-Fluorouracil or oral capecitabine was administered concurrently. Surgery was preplanned within 6 to 8 weeks. Multinomial logistic regressions for evaluation of clinical factors, Kaplan-Meier method for DFS estimation, and receiver operating characteristic analysis for determination of the optimal timeframe were used.

RESULTS

Of 279 cases, pCR was observed in 72 (25.8%). In 207 cases, pTis-4N-negative was obtained in 137 (66.2%), pT0N-positive in 6 (2.9%), and pTis-4N-positive in 64 (30.9%). The pCR group had shorter diagnosis-NCRT time (P<0.01) and on-treatment time (P=0.05). DFS was longer for pCR and partial responders with clinical stage II and III (P<0.0001). Diagnosis-NCRT time was shown different between pCR and non-pCR groups. receiver operating characteristic analysis (P<0.01) showed that a diagnosis-NCRT time of <4.5 weeks predicts pCR with a sensitivity of 88% and specificity of 81% accuracy.

CONCLUSION

The time elapsed between rectal cancer diagnosis and NCRT initiation is significantly associated with pCR. Reducing this time may increase the probability of achieving pCR.

International consensus recommendations on key outcome measures for organ preservation after (chemo)radiotherapy in patients with rectal cancer

Multimodal treatment strategies for patients with rectal cancer are increasingly including the possibility of organ preservation, through nonoperative management or local excision. Organ preservation strategies can enable patients with a complete response or near-complete clinical responses after radiotherapy with or without concomitant chemotherapy to safely avoid the morbidities associated with radical surgery, and thus to maintain anorectal function and quality of life. However, standardization of the key outcome measures of organ preservation strategies is currently lacking; this includes a lack of consensus of the optimal definitions and selection of primary end points according to the trial phase and design; the optimal time points for response assessment; response-based decision-making; follow-up schedules; use of specific anorectal function tests; and quality of life and patient-reported outcomes. Thus, a consensus statement on outcome measures is necessary to ensure consistency and facilitate more accurate comparisons of data from ongoing and future trials. Here, we have convened an international group of experts with extensive experience in the management of patients with rectal cancer, including organ preservation approaches, and used a Delphi process to establish the first international consensus recommendations for key outcome measures of organ preservation, in an attempt to standardize the reporting of data from both trials and routine practice in this emerging area.

The evaluation of follow-up strategies of watch-and-wait patients with a complete response after neoadjuvant therapy in rectal cancer

AIM

Many of the current follow-up schedules in a watch-and-wait approach include very frequent MRI and endoscopy examinations to ensure early detection of local regrowth (LR). The aim of this study was to analyse the occurrence and detection of LR in a watch-and-wait cohort and to suggest a more efficient follow-up schedule.

METHOD

Rectal cancer patients with a clinical complete response after neoadjuvant therapy were prospectively and retrospectively included in a multicentre watch-and-wait registry between 2004 and 2018, with the current follow-up schedule with 3-monthly endoscopy and MRI in the first year and 6 monthly thereafter. A theoretical comparison was constructed for the detection of LR in the current follow-up schedule against four other hypothetical schedules.

RESULTS

In all, 50/304 (16%) of patients developed a LR. The majority (98%) were detected at ≤2 years, located in the lumen (94%) and were visible on endoscopy (88%). The theoretical comparison of the different hypothetical schedules suggests that the optimal follow-up schedule should focus on the first 2 years with 3-monthly endoscopy and 3-6 monthly MRI. Longer intervals in the first 2 years will cause delays in diagnosis of LR ranging from 0 to 5 months. After 2 years, increasing the interval from 6 to 12 months did not cause important delays.

CONCLUSION

The optimal follow-up schedule for a watch-and-wait policy in patients with a clinical complete response after chemoradiation for rectal cancer should include frequent endoscopy and to a lesser degree MRI in the first 2 years. Longer intervals, up to 12 months, can be considered after 2 years.

Watch-and-wait strategy in rectal cancer: Is there a tumour size limit? Results from two pooled prospective studies

BACKGROUND

Frequency and predictive factors for a clinical complete response (cCR) in unselected patients are unclear.

MATERIAL AND METHODS

Two prospective observational studies were designed and pooled to explore predictive factors for cCR. Both studies evaluated the watch-and-wait strategy in consecutive patients; the first single-institutional study in elderly with a small tumour, the second multi-institutional study in all the patients receiving standard of care preoperative radiotherapy.

RESULTS

Four hundred and ninety patients were analysed. Short-course radiotherapy alone, or with consolidation chemotherapy or chemoradiation was given to 40.6%, 40.2% and 19.2% of the patients, respectively. The median interval from the radiation start to the first tumour response assessment was 10.2 weeks for short-course radiation and 13.2 weeks for chemoradiation. Seventy-three patients had cCR and 71 underwent w&w with the median follow-up of 24 months. The regrowth rate was 26.8%. cCR rate was 39.0% for low-risk cancer (cT1-2N0), 16.8% for intermediate-risk (cT3 with unthreatened mesorectal fascia [MRF-] or cT2N+) and 5.4% for high-risk (cT4 or MRF+). In the multivariable analysis, tumour volume (or tumour length and circumferential extent) and cN status were significant predictors for cCR. In circular cancers or with a length ≥7 cm (n = 184), cCR rate was only 2.7%, sustained cCR 1.6% and the sensitivity of cCR diagnosis 23.1%. None of 27 patients with a tumour larger than 120 cm³ achieved cCR.

CONCLUSIONS

Considering watch-and-wait strategy is questionable in patients with circular tumours or with tumour length ≥7 cm.

Local excision after (near) complete response of rectal cancer to neoadjuvant radiation: does it add value?

PURPOSE

Neoadjuvant radiotherapy is commonly used in rectal cancer. When used prior to radical surgery in locally advanced disease, up to one-quarter of patients have no residual cancer at surgery suggesting that radical surgery was unnecessary; those with complete clinical response may be managed on a rectal-preserving 'watch-and-wait' pathway. In those receiving radiotherapy for early stage cancer, local excision of small volume residual or recurrent tumour is possible, but its value is unclear.

METHODS

Data were collected from two institutions (UK and Denmark) which maintain prospective databases on all patients undergoing local excision by transanal endoscopic microsurgery (TEM). The study group was all patients who had TEM after neoadjuvant radiation for rectal cancer over an 11-year period.

RESULTS

Forty-five patients had TEM after neoadjuvant radiation, 18 after short course radiotherapy (SCRT) and 27 after chemoradiotherapy (CRT). Local recurrence occurred in 13 (29%) and distant metastases in 11 (24%). Complete pathological response was noted in 10 (22%), 28% after SCRT and 19% after CRT, p = 0.02. However, local recurrence still occurred in 60% of those with ypT0 after SCRT. The recurrence rate may be higher in those with residual disease at TEM compared with complete responders (40 vs 30%).

CONCLUSION

If complete response can be determined clinically, local excision of the scar does not confer benefit, but follow-up should be maintained. If there is regrowth or residual tumour at TEM, further recurrence is common, and the benefits of TEM may not outweigh the risks, except in those unsuitable for radical surgery.

MRI Assessment of Complete Response to Preoperative Chemoradiation Therapy for Rectal Cancer: 2020 Guide for Practice from the Korean Society of Abdominal Radiology

Objective

To provide an evidence-based guide for the MRI interpretation of complete tumor response after neoadjuvant chemoradiation therapy (CRT) for rectal cancer using visual assessment on T2-weighted imaging (T2) and diffusion-weighted imaging (DWI).

Materials and Methods

PubMed MEDLINE, EMBASE, and Cochrane Library were searched on November 28, 2019 to identify articles on the following issues: 1) sensitivity and specificity of T2 or DWI for diagnosing pathologic complete response (pCR) and the criteria for MRI diagnosis; 2) MRI alone vs. MRI combined with other test(s) in sensitivity and specificity for pCR; and 3) tests to select patients for the watch-and-wait management. Eligible articles were selected according to meticulous criteria and were synthesized.

Results

Of 1615 article candidates, 55 eligible articles (for all three issues combined) were identified. Combined T2 and DWI performed better than T2 alone, with a meta-analytic summary sensitivity of 0.62 (95% confidence interval [CI], 0.43–0.77; I² = 80.60) and summary specificity of 0.89 (95% CI, 0.80–0.94; I² = 92.61) for diagnosing pCR. The criteria for the complete response on T2 in most studies had the commonality of remarkable tumor decrease to the absence of mass-like or nodular intermediate signal, although somewhat varied, as follows: (near) normalization of the wall; regular, thin, hypointense scar in the luminal side with (near) normal-appearance or homogeneous intermediate signal in the underlying wall; and hypointense thickening of the wall. The criteria on DWI were the absence of a hyperintense signal at high b-value (≥ 800 sec/mm²) in most studies. The specific algorithm to combine T2 and DWI was obscure in half of the studies. MRI combined with endoscopy was the most utilized means to select patients for the watch-and-wait management despite a lack of strong evidence to guide and support a multi-test approach.

Conclusion

This systematic review and meta-analysis provide an evidence-based practical guide for MRI assessment of complete tumor response after CRT for rectal cancer.

Watch and wait approach in rectal cancer: Current controversies and future directions

According to the main international clinical guidelines, the recommended treatment for locally-advanced rectal cancer is neoadjuvant chemoradiotherapy followed by surgery. However, doubts have been raised about the appropriate definition of clinical complete response (cCR) after neoadjuvant therapy and the role of surgery in patients who achieve a cCR. Surgical resection is associated with significant morbidity and decreased quality of life (QoL), which is especially relevant given the favourable prognosis in this patient subset. Accordingly, there has been a growing interest in alternative approaches with less morbidity, including the organ-preserving watch and wait strategy, in which surgery is omitted in patients who have achieved a cCR. These patients are managed with a specific follow-up protocol to ensure adequate cancer control, including the early identification of recurrent disease. However, there are several open questions about this strategy, including patient selection, the clinical and radiological criteria to accurately determine cCR, the duration of neoadjuvant treatment, the role of dose intensification (chemotherapy and/or radiotherapy), optimal follow-up protocols, and the future perspectives of this approach. In the present review, we summarize the available evidence on the watch and wait strategy in this clinical scenario, including ongoing clinical trials, QoL in these patients, and the controversies surrounding this treatment approach.

How to measure tumour response in rectal cancer? An explanation of discrepancies and suggestions for improvement

Various methods categorize tumour response after neoadjuvant therapy, including down-staging and tumour regression grading. Response categories allow comparison of different treatments within clinical trials and predict outcome. A reproducible response categorization could identify subgroups with high or low risk for the most appropriate subsequent treatments, like watch and wait. Lack of standardization and interpretation difficulties currently limit the usability of these approaches. In this review we describe these difficulties for the evaluation of chemoradiation in rectal cancer. An alternative approach of tumour response is based on patterns of residual disease, including fragmentation. We summarise the evidence behind this alternative method of response categorisation, which explains a number of very relevant clinical discrepancies. These issues include differences between downstaging and tumour regression, high local regrowth in advanced tumours during watchful waiting procedures, the importance of resection margins, the limited value of post-treatment biopsies and the relatively poor outcome of patients with a near complete pathological response. Recognition of these patterns of response can allow meaningful development of novel biomarkers in the future.

Value of intra-tumor heterogeneity evaluated by diffusion-weighted MRI for predicting pathological stages and therapeutic responses to chemoradiotherapy in lower rectal cancer

Aim: Diffusion-weighted MRI (DWI) has the potential to reveal intra-tumor structural heterogeneity consisting of stroma through an evaluation of uniformity on DWI. In present study, we examined the diagnostic value of intra-tumor heterogeneity evaluated by DWI in lower rectal cancer (LRC).

Patients and Methods: A total of 172 LRC patients underwent radical surgery between 2009 and 2017. T1 tumors and cases without pre-operative MRI were excluded. Twenty-nine primary resection cases (PR) and 37 pre-operative chemoradiotherapy followed by radical surgery cases (pCRT) were targeted. Intra-tumor heterogeneity on DWI was quantified using a specific formula (HSD). Structural heterogeneity was objectively quantified by an image analysis of resected specimens using a digital microscope (HSP). The relationships between HSD and HSP, pathological factors, and tumor regression grades (TRG) of pCRT were evaluated.

Results: The relationship between HSD and HSP was analyzed by a linear regression model in PR cases, revealing a positive correlation (R²=0.43). PR cases were divided into HSD-high and HSD-low according to the median. There were more pT3 or N(+) cases in HSD-high (p=0.038, 0.095). HSD before pCRT correlated with TRG (grade 1 versus 2/3) in pCRT cases (p=0.001). The diagnostic accuracy of HSD for predicting T and N stages and therapeutic grades was evaluated by cut-off values calculated using a ROC curve and revealed that each factor may be accurately diagnosed.

Conclusion: Intra-tumor heterogeneity on DWI corresponded with stromal pathological heterogeneity. It is useful for predicting T3 or deeper tumor invasion, pathological N(+), and the therapeutic effects of pCRT.

Wait-and-see treatment strategies for rectal cancer patients with clinical complete response after neoadjuvant chemoradiotherapy: a systematic review and meta-analysis

Wait-and-see treatment strategies may benefit rectal cancer patients who achieve a clinical complete response (cCR) after neoadjuvant chemoradiotherapy (NCRT). In this study, we analyzed data from 9 eligible trials to compare the oncologic outcomes of 251 rectal cancer patients achieving a cCR through nonsurgical management approaches with the outcomes of 344 patients achieving a pathologic complete response (pCR) through radical surgery. The two patient groups did not differ in distant metastasis rates or disease-free and overall survival, but the nonsurgical group had a higher risk of 1, 2, 3, and 5-year local recurrence. Hence, we concluded that for rectal cancer patients achieving a cCR after NCRT, a wait-and-see strategy with strict selection criteria, an appropriate follow-up schedule, and salvage treatments achieved outcomes at least as good as radical surgery. Long-term randomized and controlled trials with more uniform inclusion criteria and standardized follow-up schedules will help clarify the risks and benefits of wait-and-see treatment strategies for these patients.

Sequential PET/CT with [18F]-FDG Predicts Pathological Tumor Response to Preoperative Short Course Radiotherapy with Delayed Surgery in Patients with Locally Advanced Rectal Cancer Using Logistic Regression Analysis

Previous studies indicate that FDG PET/CT may predict pathological response in patients undergoing neoadjuvant chemo-radiotherapy for locally advanced rectal cancer (LARC). Aim of the current study is evaluate if pathological response can be similarly predicted in LARC patients after short course radiation therapy alone. Methods: Thirty-three patients with cT2-3, N0-2, M0 rectal adenocarcinoma treated with hypo fractionated short course neoadjuvant RT (5x5 Gy) with delayed surgery (SCRTDS) were prospectively studied. All patients underwent 3 PET/CT studies at baseline, 10 days from RT end (early), and 53 days from RT end (delayed). Maximal standardized uptake value (SUVmax), mean standardized uptake value (SUVmean) and total lesion glycolysis (TLG) of the primary tumor were measured and recorded at each PET/CT study. We use logistic regression analysis to aggregate different measures of metabolic response to predict the pathological response in the course of SCRTDS. Results: We provide straightforward formulas to classify response and estimate the probability of being a major responder (TRG1-2) or a complete responder (TRG1) for each individual. The formulas are based on the level of TLG at the early PET and on the overall proportional reduction of TLG between baseline and delayed PET studies. Conclusions: This study demonstrates that in the course of SCRTDS it is possible to estimate the probabilities of pathological tumor responses on the basis of PET/CT with FDG. Our formulas make it possible to assess the risks associated to LARC borne by a patient in the course of SCRTDS. These risk assessments can be balanced against other health risks associated with further treatments and can therefore be used to make informed therapy adjustments during SCRTDS.

Effect of Interval between Neoadjuvant Chemoradiotherapy and Surgery on Oncological Outcome for Rectal Cancer: A Systematic Review and Meta-Analysis

Aim. To evaluate the influence of interval between neoadjuvant chemoradiotherapy (NCRT) and surgery on oncological outcome. Methods. A systematic search was conducted in PubMed, the Cochrane Library, and Embase databases for publications reporting oncological outcomes of patients following rectal cancer surgery performed at different NCRT-surgery intervals. Relative risk (RR) of pathological complete response (pCR) among different intervals was pooled. Results. Fifteen retrospective cohort studies representing 4431 patients met the inclusion criteria. There was a significantly increased rate of pCR in patients treated with surgery followed 7 or 8 weeks later (RR, 1.45; 95% CI, 1.18-1.78; and P < 0.01 and RR, 1.49; 95% CI, 1.15-1.92; and P = 0.002, resp.). There is no consistent evidence of improved local control or overall survival with longer or shorter intervals. Conclusion. Performing surgery 7-8 weeks after the end of NCRT results in the highest chance of achieving pCR. For candidates of abdominoperineal resection before NCRT, these data support implementation of prolonging the interval after NCRT to optimize the chances of pCR and perhaps add to the possibility of ultimate organ preservation.