Restaging rectal cancer following neoadjuvant chemoradiotherapy

Correct tumour restaging is pivotal for identifying the most personalised surgical treatment for patients with locally advanced rectal cancer undergoing neoadjuvant therapy, and works to avoid both poor oncological outcome and overtreatment. Digital rectal examination, endoscopy, and pelvic magnetic resonance imaging are the recommended modalities for local tumour restaging, while chest and abdominal computed tomography are utilised for the assessment of distant disease. The optimal length of time between neoadjuvant treatment and restaging, in terms of both oncological safety and clinical effectiveness of treatment, remains unclear, especially for patients receiving prolonged total neoadjuvant therapy. The timely identification of patients who are radioresistant and at risk of disease progression remains challenging.

Changing patterns of neoadjuvant therapy for locally advanced rectal cancer: A narrative review

Standard treatment for patients with locally advanced rectal cancer has been the multidisciplinary approach of neoadjuvant chemoradiotherapy, followed by total mesorectal excision (TME) and postoperative adjuvant chemotherapy. This reduces the local recurrence rate, but the challenge of distant metastasis still persists. The improvement in treatment approach has always been the focus of clinical research and studies have been conducted worldwide in recent years. On one hand, evidence suggests that increasing the intensity of treatment can result in better tumor regression, for example by adding a second drug to the neoadjuvant chemoradiotherapy, or extending the interval between neoadjuvant therapy and surgery, or incorporating chemotherapy and chemoradiotherapy in the neoadjuvant setting. On the other hand, neoadjuvant immunotherapy and selective omission of neoadjuvant radiotherapy may improve the quality of life of patients. In this article, we review the key clinical research progresses in neoadjuvant therapy for locally advanced rectal cancer, hoping to provide some valuable views on the individualized treatment for rectal cancer.

The Multimodal Management of Locally Advanced Rectal Cancer: Making Sense of the New Data

In the past 40 years, the treatment of locally advanced rectal cancer has evolved with the addition of radiotherapy or chemoradiotherapy and providing (neo)adjuvant systemic chemotherapy to major surgery. However, recent trends have focused on improving our ability to risk-stratify patients and tailoring treatment to achieve the best oncologic outcome while limiting the impact on long-term quality of life. Therefore, there has been increasing interest in pursuing a watch-and-wait approach to achieve organ preservation. Several retro- and prospective studies suggest safety of the watch-and-wait approach, though it is still considered controversial due to limited clinical evidence, concerns about tumor regrowth, and subsequent distant progression. To further reduce treatment, MRI risk stratification, together with patient characteristics and patient preferences, can guide personalized treatment and reserve radiation and chemotherapy for a select patient population. Ultimately, improved options for reassessment during neoadjuvant treatment may allow for more adaptive therapy options based on treatment response. This article provides an overview of some major developments in the multimodal treatment of locally advanced rectal cancer. It reviews some relevant, controversial issues of the watch-and-wait approach and opportunities to personally tailor and reduce treatment. It also reviews the overall neoadjuvant treatment, including total neoadjuvant therapy trials, and how to best optimize for a potential complete response. Finally, it provides an algorithm as an example of how such a personalized, tailored, adaptive, and reduced treatment could look like in the future.

Current status of total neoadjuvant therapy for locally advanced rectal cancer

Neoadjuvant chemoradiotherapy (nCRT) plus total mesorectal excision (TME) has been the standard regimen for treatment of patients with locally advanced rectal cancer (LARC), because it significantly reduces the rate of local recurrence and enables sphincter preservation. However, distant metastasis remains the major reason for treatment failure, and the value of postoperative chemotherapy is still controversial. Recent studies have examined the use of total neoadjuvant therapy (TNT), defined as induction and/or consolidation chemotherapy (CONCT) with radiotherapy (RT) or nCRT prior to surgery. The results indicated that TNT may increase the rates of chemotherapy compliance and pathological complete response (pCR), and probably improve the success rate of sphincter preservation surgery. TNT may also improve disease-free survival and overall survival, and even reduce the rate of relapse. Here, we critically appraise the existing literature on three different TNT schemes used for LARC patients.

Evaluation and Predictive Factors of Complete Response in Rectal Cancer after Neoadjuvant Chemoradiation Therapy

The response to neoadjuvant chemoradiation therapy is an important prognostic factor for locally advanced rectal cancer. Although the majority of the patients after neoadjuvant therapy are referred to following surgery, the clinical data show that complete clinical or pathological response is found in a significant proportion of the patients. Diagnostic accuracy of confirming the complete response has a crucial role in further management of a rectal cancer patient. As the rate of clinical complete response, unfortunately, is not always consistent with pathological complete response, accurate diagnostic parameters and predictive markers of tumor response may help to guide more personalized treatment strategies and identify potential candidates for nonoperative management more safely. The management of complete response demands interdisciplinary collaboration including oncologists, radiotherapists, radiologists, pathologists, endoscopists and surgeons, because the absence of a multidisciplinary approach may compromise the oncological outcome. Prediction and improvement of rectal cancer response to neoadjuvant therapy is still an active and challenging field of further research. This literature review is summarizing the main, currently known clinical information about the complete response that could be useful in case if encountering such condition in rectal cancer patients after neoadjuvant chemoradiation therapy, using as a source PubMed publications from 2010–2021 matching the search terms “rectal cancer”, “neoadjuvant therapy” and “response”.

Time interval between neoadjuvant radio-chemotherapy and surgery in rectal cancer: is the long interval correct for all patients?

BACKGROUND

Optimal time between neoadjuvant radio-chemotherapy period and surgery remains controversial in patients with rectal cancer: an increasing number of studies show results in favour of a long interval.

METHODS

We conducted a retrospective analysis of the cases of low-middle rectal adenocarcinoma undergoing neoadjuvant RT-CT and surgery: the primary endpoint was the complete pathological response rate and the secondary endpoint the rate of complications. We analysed cases from 1/01/2003 to 31/12/2018 divided in two periods: from 2003 to 2010 (23 pts) and from 2011 to 2018 (23 pts). The two periods were characterised by two different surgical teams which use different time intervals (≤vs>8 weeks).

RESULTS

The pCR rate is 21.7% in both groups; as regards the complications, the difference between the two groups is in grade IIIb: 8.7% in the first group and 17.4% in the second group (p 0.66).

CONCLUSIONS

Although our study is based on a small number of patients, it shows the same rate of pCR with respect to two different time intervals; this suggests the need for studies based on the division of patients into subgroups and the evaluation of different time intervals in order to reach the best oncological outcomes.

Improved response rate in patients with prognostically poor locally advanced rectal cancer after treatment with induction chemotherapy and chemoradiotherapy when compared with chemoradiotherapy alone: A matched case-control study

INTRODUCTION

The addition of induction chemotherapy (ICT) to neoadjuvant chemoradiotherapy (CRT) has the potential to improve outcomes in patients with locally advanced rectal cancer (LARC). However, patient selection is essential to prevent overtreatment. This study compared the complete response (CR) rate after treatment with and without ICT of LARC patients with prognostically poor characteristics.

METHODS

All LARC patients who were treated with neoadjuvant CRT, whether or not preceded by ICT, and who underwent surgery or were considered for a wait-and-see strategy between January 2016 and March 2020 in the Catharina Hospital Eindhoven, were retrospectively selected. LARC was defined as any T4 tumour, or a T2/T3 tumour with extramural venous invasion and/or tumour deposits and/or N2 lymph node status, and/or mesorectal fascia involvement (T3 tumours only). Case-control matching was performed based on the aforementioned characteristics.

RESULTS

Of 242 patients, 178 (74%) received CRT (CRT-group) and 64 patients (26%) received ICT followed by CRT (ICT-group). In the ICT-group, 3 patients (5%) did not receive the minimum of three cycles. In addition, in this selected cohort, compliance with radiotherapy was 100% in the ICT-group and 97% in the CRT-group. The CR rate was 30% in the ICT-group and 15% in the CRT-group (p = 0.011). After case-control matching, the CR rate was 28% and 9%, respectively (p = 0.013).

CONCLUSION

Treatment including ICT seemed well tolerated and resulted in a high CR rate. Hence, this treatment strategy may facilitate organ preservation and improve survival in LARC patients with prognostically poor characteristics.

Deep regional hyperthermia with preoperative radiochemotherapy in locally advanced rectal cancer, a prospective phase II trial

PURPOSE

The goal of the present study was to investigate the effect of deep regional hyperthermia on early and long-term oncological outcomes in the context of preoperative radiochemotherapy in rectal cancer.

METHODS

In this prospective phase II trial, patients with locally advanced rectal cancer were treated with 5-fluorouracil based preoperative radiochemotherapy with 50.4 Gy in 28 fractions. Deep regional hyperthermia was scheduled twice weekly. Pathological tumor regression was scored according to the Dworak regression system. The primary endpoint was pathological complete response (pCR). Further endpoints were local control (LC), distant control (DC), disease-free survival (DFS) and overall survival (OS). Hyperthermia was defined as feasible if 70% of patients received at least eight treatments. Quality of life was assessed at follow-up by the EORTC-QLQ-C30 and QLQ-CR29 questionnaires. Time to event data was analyzed according to Kaplan-Meier based on first-events. The study was registered on clinicaltrials.gov (NCT02353858).

RESULTS

From 2012 until 2017, 78 patients were recruited. Median follow-up was 54 months. Based on magnetic resonance imaging, the mesorectal fascia was involved or threatened in 60% of the patients. Compliance with radiotherapy was 99%, 91% received both cycles of chemotherapy and 77% had eight or more hyperthermia treatments. Median time from the end of radiotherapy to surgery was 6.7 weeks. A pathological complete response was reported in 14% of the patients, 50% had either Dworak 4 (complete regression) or Dworak 3 regression (scattered tumor cells only). Three year estimates for OS, DFS, LC and DC were 94%, 81%, 96% and 87%. Patients with higher hyperthermia related cumulative temperatures showed stronger tumor regression. Global health status based on EORTC-QLQ-C30 was comparable with data from the general population.

CONCLUSION

Deep regional hyperthermia was feasible, did not compromise standard treatments and resulted in promising long-term oncological outcomes and QoL.

Total neoadjuvant therapy for rectal cancer: Making sense of the results from the RAPIDO and PRODIGE 23 trials

A few months ago, results from two randomised phase III trials of total neoadjuvant therapy (TNT) in locally advanced rectal cancer were presented (RAPIDO and PRODIGE 23), consistently showing better short- and long-term outcomes with TNT as compared with standard neoadjuvant long-course chemoradiotherapy (CRT) or short-course radiotherapy (SCRT). These results represent corroborating evidence in support of a practice that many centres had already implemented based on promising preliminary data. Also, they provide new, high-level evidence to endorse TNT as a new management option in the treatment algorithm of stage II-III rectal cancer in those centres where CRT and SCRT have long remained the only accepted standard neoadjuvant treatments. Having two consistently positive trials is certainly reassuring regarding the potential of TNT as a general treatment approach. Nevertheless, substantial differences between these trials pose important challenges in relation to the generalisability and applicability of their results, and translation of the same into practical clinical recommendations. In this article, we address a number of key questions that the RAPIDO and PRODIGE 23 trials have raised among the broad community of gastrointestinal oncologists, proposing an interpretation of the data that may help the decision making, and highlighting grey areas that warrant further investigation.

Outcome measures in multimodal rectal cancer trials

There is a large variability regarding the definition and choice of primary endpoints in phase 2 and phase 3 multimodal rectal cancer trials, resulting in inconsistency and difficulty of data interpretation. Also, surrogate properties of early and intermediate endpoints have not been systematically assessed. We provide a comprehensive review of clinical and surrogate endpoints used in trials for non-metastatic rectal cancer. The applicability, advantages, and disadvantages of these endpoints are summarised, with recommendations on clinical endpoints for the different phase trials, including limited surgery or non-operative management for organ preservation. We discuss how early and intermediate endpoints, including patient-reported outcomes and involvement of patients in decision making, can be used to guide trial design and facilitate consistency in reporting trial results in rectal cancer.

SPAR - a randomised, placebo-controlled phase II trial of simvastatin in addition to standard chemotherapy and radiation in preoperative treatment for rectal cancer: an AGITG clinical trial

BACKGROUND

Retrospective studies show improved outcomes in colorectal cancer patients if taking statins, including overall survival, pathological response of rectal cancer to preoperative chemoradiotherapy (pCRT), and reduced acute and late toxicities of pelvic radiation. Major tumour regression following pCRT has strong prognostic significance and can be assessed in vivo using MRI-based tumour regression grading (mrTRG) or after surgery using pathological TRG (pathTRG).

METHODS

A double-blind phase 2 trial will randomise 222 patients planned to receive long-course fluoropyrimidine-based pCRT for rectal adenocarcinoma at 18+ sites in New Zealand and Australia. Patients will receive simvastatin 40 mg or placebo daily for 90 days starting 1 week prior to standard pCRT. Pelvic MRI 6 weeks after pCRT will assess mrTRG grading prior to surgery. The primary objective is rates of favourable (grades 1-2) mrTRG following pCRT with simvastatin compared to placebo, considering mrTRG in 4 ordered categories (1, 2, 3, 4-5). Secondary objectives include comparison of: rates of favourable pathTRG in resected tumours; incidence of toxicity; compliance with intended pCRT and trial medication; proportion of patients undergoing surgical resection; cancer outcomes and pathological scores for radiation colitis. Tertiary objectives include: association between mrTRG and pathTRG grouping; inter-observer agreement on mrTRG scoring and pathTRG scoring; studies of T-cell infiltrates in diagnostic biopsies and irradiated resected normal and malignant tissue; and the effect of simvastatin on markers of systemic inflammation (modified Glasgow prognostic score and the neutrophil-lymphocyte ratio). Trial recruitment commenced April 2018.

DISCUSSION

When completed this study will be able to observe meaningful differences in measurable tumour outcome parameters and/or toxicity from simvastatin. A positive result will require a larger RCT to confirm and validate the merit of statins in the preoperative management of rectal cancer. Such a finding could also lead to studies of statins in conjunction with chemoradiation in a range of other malignancies, as well as further exploration of possible mechanisms of action and interaction of statins with both radiation and chemotherapy. The translational substudies undertaken with this trial will provisionally explore some of these possible mechanisms, and the tissue and data can be made available for further investigations.

TRIAL REGISTRATION

ANZ Clinical Trials Register ACTRN12617001087347. (www.anzctr.org.au, registered 26/7/2017) Protocol Version: 1.1 (June 2017).

Formation of Polyploid Giant Cancer Cells Involves in the Prognostic Value of Neoadjuvant Chemoradiation in Locally Advanced Rectal Cancer

We previously reported that polyploid giant cancer cells (PGCCs) exhibit cancer stem cell properties and can generate daughter cells with the epithelial-mesenchymal transition phenotype. This study investigated the role of PGCC formation in the prognostic value of neoadjuvant chemoradiation therapy (nCRT) in locally advanced rectal cancer (LARC). The morphological characteristics were observed in patients with LARC after nCRT. Colorectal cancer cell lines were treated with irradiation or chemotherapeutic drugs, and the metastasis-related proteins were detected. 304 nCRT cases and 301 paired non-nCRT cases were collected for analysis. More PGCCs and morphologic characteristics related to invasion and metastasis appeared in tumor tissue after nCRT. Irradiation or chemicals could induce the formation of PGCCs with daughter cells exhibiting strong migratory, invasive, and proliferation abilities. In patients after nCRT, pathologic complete remission, partial remission, stable disease, and progressive disease were observed in 29 (9.54%), 125 (41.12%), 138 (45.39%), and 12 (3.95%) patients, respectively. Mucinous adenocarcinomas (MCs) occurred more frequently in nCRT than in non-nCRT patients (χ ² = 29.352, P=0.001), and the prognosis in MC patients was worse than that in non-MC patients (χ ² = 24.617, P=0.001). The difference in survival time had statistical significance for 60 days (χ ² = 5.357, P=0.021) and 70 days (χ ² = 18.830, P=0.001) rest interval time. On multivariable analysis, 60 days rest interval, Duke's stage, and recurrence and/or distant metastasis remained significant predictors of survival. In conclusion, irradiation or chemicals induce the formation of PGCCs and PGCCs produce daughter cells with strong migration and invasion abilities after a long incubation period. Appropriate rest interval (incubation period) is very important for patients with LARC who will receive nCRT.

Locally Advanced Rectal Cancer Evaluation by Magnetic Resonance Imaging after Neoadjuvant Therapy on Decision Making: Cancer Center Experience and Literature Review

PURPOSE

An accurate clinical and radiological staging is the pyramid of treatment decisions in locally advanced rectal cancer (LARC). Guidelines recommended neoadjuvant chemoradiation therapy (CRT) followed by surgical resection for fit patients with LARC. Determining the aggressiveness of intervention while avoiding needless morbidity according to patient risk remains an unmet pre-operative decision-making need. With newer magnetic resonance imaging (MRI) techniques and image acquisition available at our Cancer Center, we seek to retrospectively review the correlation between pre- and post-CRT MRI response to the surgical pathological stage in order to aide multidisciplinary team decision making.

METHODS

Our Cancer Center Rectal Cancer Registry between 2011 and 2015 included 57 patients with LARC, 20 completed standard CRT with surgery, and of those 10 had repeated MRI after CRT.

RESULTS

Our retrospective case series revealed that 90% of the patients had a downstage tumor response on surgical specimen compared to radiological evaluation after CRT, and furthermore, all patients who were re-staged with MRI prior to surgery correlated with the gold standard pathological stage (p = 0.02).

CONCLUSIONS

Post-CRT MRI could potentially aide decision making to further avoid 20% of patients with a complete pathological response from a morbid surgery, whereas 10% of patients with an upstaged disease state may require a more aggressive neoadjuvant or planned surgical intervention. We concluded that future multidisciplinary oncology care treatment decision making would benefit from a repeat MRI after neoadjuvant CRT of LARC.

How to Achieve a Higher Pathologic Complete Response in Patients With Locally Advanced Rectal Cancer Who Receive Preoperative Chemoradiation Therapy

The current standard of care for treating patients with locally advanced rectal cancer includes preoperative chemoradiation therapy (PCRT) followed by a total mesorectal excision and postoperative adjuvant chemotherapy. A subset of these patients has achieved a pathologic complete response (pCR) and they have shown improved disease-free and overall survival compared to non-pCR patients. Thus, many efforts have been made to achieve a higher pCR through PCRT. In this review, results from various ongoing and recently completed clinical trials that are being or have been conducted with an aim to improve tumor response by modifying therapy will be discussed.

Randomized clinical trial of short or long interval between neoadjuvant chemoradiotherapy and surgery for rectal cancer

BACKGROUND

The optimal timing of surgery following preoperative chemoradiotherapy (CRT) is controversial. This trial aimed to compare pathological complete response (pCR) rates obtained after an interval of 8 weeks or less versus more than 8 weeks.

METHODS

Patients with locally advanced rectal adenocarcinoma situated within 12 cm of the anal verge (T3-4 or N+ disease) were randomized to undergo total mesorectal excision (TME) within 8 weeks (classical interval, CI group) or after 8 weeks (long interval, LI group) following CRT.

RESULTS

Among the 327 included patients (CI 160, LI 167), the pCR rate was significantly higher in the LI group than in the CI group (10·0 versus 18·6 per cent; P = 0·027). The highest pCR rate (29 per cent) was observed between 10 and 11 weeks. There was statistically significant disease regression in the LI group, with better stage (P = 0·004) and T category (P = 0·001) than in the CI group. There was no significant difference in surgical quality (rates of tumour-positive margins, TME quality, anastomotic leakage and intraoperative perforation) between the groups. The overall morbidity rate was 22·5 per cent in the CI group and 19·8 per cent in the LI group (P = 0·307). Regression analysis including sex, age, clinical stage, tumour location, tumour differentiation, TME quality, concomitant chemotherapy and interval to surgery revealed no statistically significant predictors of pCR.

CONCLUSION

Disease regression and pCR rate are increased with an interval between CRT and surgery exceeding 8 weeks. Registration number: NCT03287843 (http://www.clinicaltrials.gov).

Watch-and-Wait as a Therapeutic Strategy in Rectal Cancer

Purpose of Review

Pathological complete response is seen in approximately one fifth of rectal cancer patients following neoadjuvant chemoradiation. Since these patients have excellent oncological outcomes, there has been a rapidly growing interest in organ preservation for those who develop a clinical complete response. We review the watch-and-wait strategy and focus on all aspects of this hot topic, including who should be considered for this approach, how should we identify treatment response and what are the expected outcomes.

Recent Findings

The major challenges in interpreting the data on watch-and-wait are the significant heterogeneity of patients selected for this approach and of methods employed to identify them. The evidence available comes mostly from retrospective cohort studies, but has shown good oncological outcomes, including the rate of successful salvage surgery, locoregional control and overall survival.

Summary

There is currently not enough and not robust enough evidence to support watch-and-wait as a standard approach, outside a clinical trial, for patients achieving clinical complete response following neoadjuvant chemoradiation. Furthermore, there is a lack of data on long-term outcomes. However, the results we have so far are promising, and there is therefore an urgent need for randomised control studies such as the TRIGGER trial to confirm the safety of this strategy.

The Impact of Surgical Timing on Pathologic Tumor Response after Short Course and Long Course Preoperative Chemoradiation for Locally Advanced Rectal Adenocarcinoma

Purpose

A pooled analysis of multi-institutional trials was performed to analyze the effect of surgical timing on tumor response by comparing short course concurrent chemoradiotherapy (CCRT) with long course CCRT followed by delayed surgery in locally advanced rectal cancer.

Materials and Methods

Three hundred patients with cT3-4N0-2 rectal adenocarcinoma were included. Long course patients from KROG 14-12 (n=150) were matched 1:1 to 150 short course patients from KROG 10-01 (NCT01129700) and KROG 11-02 (NCT01431599) according to stage, age, and other risk factors. The primary endpoint was to determine the interval between surgery and the last day of neoadjuvant CCRT which yields the best tumor response after the short course and long course CCRT. Downstaging was defined as ypT0-2N0M0 and pathologic complete response (ypCR) was defined as ypT0N0M0, respectively.

Results

Both the long and short course groups achieved lowest downstaging rates at < 6 weeks (long 20% vs. short 8%) and highest downstaging rates at 6-7 weeks (long 44% vs. short 40%). The ypCR rates were lowest at < 6 weeks (both long and short 0%) and highest at 6-7 weeks (long 21% vs. short 11%) in both the short and long course arms. The downstaging and ypCR rates of long course group gradually declined after the peak at 6-7 weeks and those of the short course group trend to constantly increase afterwards.

Conclusion

It is optimal to perform surgery at least 6 weeks after both the short course and long course CCRT to obtain maximal tumor regression in locally advanced rectal adenocarcinoma.

Organ preservation in rectal cancer - Challenges and future strategies

Neoadjuvant radiochemotherapy with subsequent total mesorectal excision is the standard of care for locally advanced rectal cancer. While this multimodal strategy has decreased local recurrences rates below 5%, long-term morbidities are considerable in terms of urinary, sexual or bowel functioning. At the same time approximately 10–20% of patients have no evidence of residual tumour in their surgical specimen. Pioneering studies from Brazil have suggested that surgery can safely be omitted in carefully selected patients with a clinical complete response after radiochemotherapy. Although confirmatory studies showed similar results, challenges in terms of optimizing radiochemotherapy for organ-preservation, appropriate selection of patients for non-operative management and the safety of this approach remain. The present review will summarize the current data on organ-preservation in rectal cancer and discuss the challenges that need to be addressed in future trials.