Predicting complete response to neoadjuvant CRT for distal rectal cancer using sequential PET/CT imaging

Safety and clinical efficacy of neoadjuvant chemoradiation therapy with immunotherapy for organ preservation in ultra-low rectal cancer: preliminary results of the CHOICE-I trial: a prospective cohort study

OBJECTIVE

To explore the safety and efficacy of neoadjuvant chemoradiotherapy (nCRT) combined with a PD-1 antibody in improving complete clinical response (cCR) and organ preservation in patients with ultra-low rectal cancer.

METHODS

This was a prospective phase II, single-arm, open-label trial. Patients with confirmed pMMR status T 1-3a N 0-1 M 0 retcal adenocarcinoma were included. Long-course chemoradiotherapy was delivered to a dose of 50 Gy. A PD-1 antibody was added 2 weeks after the first radiotherapy session, and two courses were administered. After chemoradiotherapy, CapeOX plus PD-1 antibody was administered to patients for two cycles. After evaluation, patients with cCR were managed with a watch-and-wait (W&W) approach. Local excision or a W&W approach was performed for patients with near complete clinical response (ncCR) as per multidisciplinary team decision. Radical surgery was recommended for poorly regressed or progressed tumors.

RESULTS

Twenty-five patients were enrolled, but two patients withdrew from the study. A total of 23 patients completed the entire neoadjuvant therapy. Ten and five patients achieved cCR and ncCR, respectively, and the rest had a partial clinical response. Patients with cCR were managed with W&W. Four patients with ncCR underwent local excision and were managed using W&W. Eight patients with partial clinical response underwent anus-preserving surgery. At the last follow-up, the rectum and anus preservation rates were 63.4% (14/22) and 95.5% (21/22), respectively.

CONCLUSION

nCRT combined with immunotherapy tended to achieve better cCR and rectum preservation rates with good tolerance in patients.

Is Early, Postinduction Restaging of Rectal Cancer Undergoing Total Neoadjuvant Therapy Associated With Ultimate Treatment Response?

BACKGROUND

Among patients with rectal cancer treated with total neoadjuvant therapy, it is unclear whether early, postinduction restaging is associated with final tumor response. If so, interim restaging may alter rectal cancer decision-making.

OBJECTIVE

To determine whether postinduction restaging with endoscopy and MRI is associated with final tumor response.

DESIGN

Retrospective cohort study.

SETTINGS

US tertiary care institution accredited by the National Accreditation Program for Rectal Cancer.

PATIENTS

Patients with biopsy-proven rectal cancer who underwent total neoadjuvant therapy with interim (postinduction) restaging.

MAIN OUTCOME MEASURES

Association between response assessment on postinduction restaging and final treatment response.

RESULTS

One hundred seven patients were analyzed. Patients with postinduction magnetic resonance tumor response grade 1 and 2 or complete endoscopic response were significantly more likely (OR 5.4, p < 0.01 and OR 3.7, p = 0.03, respectively) to ultimately achieve a final complete response. Likewise, the odds of a final incomplete response were significantly higher for patients with postinduction composite partial (OR 4.1, p < 0.01) or minimal (OR 12.0, p < 0.01) responses.

LIMITATIONS

Retrospective analysis and lack of detailed subclassification of partial endoscopic response may have limited the conclusions of these data. The limited sample size may also have biased these conclusions.

CONCLUSIONS

Tumor response to induction therapy is associated with the ultimate treatment response to total neoadjuvant therapy among complete or minimal responders; the significance of a partial interim response remains unclear. See Video Abstract .

EST ASOCIADA LA REESTADIFICACIN TEMPRANA POSTINDUCCIN DEL CANCER DE RECTO SOMETIDO A TERAPIA NEOADYUVANTE TOTAL CON LA RESPUESTA TERAPUTICA FINAL

ANTECEDENTES:Entre los pacientes con cáncer de recto tratados con terapia neoadyuvante total, no está claro si la re-estadificación temprana posterior a la inducción está asociada con la respuesta tumoral final. De ser así, la re-estadificación provisoria podría alterar la toma de decisiones sobre el cáncer rectal.OBJETIVO:Determinar si la re-estadificación posterior a la inducción con endoscopia y resonancia magnética están asociadas con la respuesta tumoral final.DISEÑO:Estudio de cohorte retrospectivoESCENARIO:Institución de atención terciaria de Estados Unidos, certificada por el Programa Nacional de Acreditación para el Cáncer de Recto.PACIENTES:Pacientes con cáncer rectal confirmado por biopsia que fueron sometidos a terapia neoadyuvante total con re-estadificación provisoria (posterior a la inducción).PRINCIPALES MEDIDAS DE RESULTADOS:La asociación entre la evaluación de la respuesta en la re-estadificación posterior a la inducción y la respuesta al final del tratamiento.RESULTADOS:Se estudiaron 107 pacientes. Aquellos que presentaban respuesta tumoral a la resonancia magnética post-inducción grado 1-2 o respuesta endoscópica completa tuvieron significativamente más probabilidades (OR (odds ratio) 5,4 [ p < 0,01] y OR: 3,7 [ p = 0,03], respectivamente) de lograr finalmente una respuesta completa final. Asimismo, las probabilidades de una respuesta incompleta final fueron significativamente mayores para los pacientes con respuestas parciales compuestas post-inducción (OR: 4,1, p < 0,01) o mínimas (OR: 12,0, p < 0,01).LIMITACIONES:El análisis retrospectivo y la falta de una subclasificación detallada de la respuesta endoscópica parcial pueden haber limitado las conclusiones de estos datos. El tamaño limitado de la muestra también puede haber sesgado las conclusiones mencionadas.CONCLUSIÓN:La respuesta tumoral a la terapia de inducción está asociada con la respuesta final al tratamiento con terapia neoadyuvante total entre los respondedores completos o mínimos; la importancia de una respuesta parcial provisional sigue sin estar clara. (Traducción-Dr. Xavier Delgadillo ).

A management of patients achieving clinical complete response after neoadjuvant therapy and perspectives: on locally advanced rectal cancer

Neoadjuvant chemoradiotherapy (nCRT) followed by total mesorectal excision (TME) and selective use of adjuvant chemotherapy is currently considered the standard of care for locally advanced rectal cancer (LARC). Despite this, the concept of organ preservation is gradually challenging this approach. The management of complete clinical remission (cCR) lacks international consensus, leading scholars to develop their own perspectives based on well-designed studies and long-term data from large multicenter cohorts. To ensure appropriate treatment, this review focuses on the choice of neoadjuvant therapy, criteria for defining cCR, and treatment strategies for patients who achieve cCR after neoadjuvant therapy. By providing guidance on the accurate management of LARC patients after cCR, this review aims to prevent over- or under-treatment.

Outcomes of Postchemoradiotherapy Watch-and-Wait Strategy in Patients With Rectal Cancer: A 20-Year, Single-Center Study

BACKGROUND AND OBJECTIVES

The watch-and-wait (WW) strategy is a nonsurgical alternative for patients with rectal cancer exhibiting an excellent response to chemoradiotherapy. Studies on the WW strategy have primarily investigated 5-year oncological outcomes; few have focused on longer-term outcomes or the optimal patient selection approach for this therapeutic strategy.

METHODS

This retrospective study enrolled patients with locally advanced rectal adenocarcinoma who had achieved complete response after chemoradiotherapy. Patients who achieved pathological complete response were categorized into a control group (n = 95) and those who achieved clinical complete response and were managed using the WW strategy were categorized into a case group (n = 33). Kaplan-Meier estimates were calculated for the between-group comparison of survival.

RESULTS

The median follow-up duration was 89 months. Compared with the control group, the case group exhibited improved long-term sphincter preservation, particularly for low-lying tumors (p = 0.032), and inferior nonlocal-regrowth disease-free survival (p = 0.007). Within the case group, patients achieving a complete response by positron emission tomography exhibited 5-year survival rates similar to those achieving a complete endoscopic response.

CONCLUSION

The WW strategy is associated with improved sphincter preservation but worse nonlocal-regrowth disease-free survival. The potential of PET in patient selection for this strategy deserves further investigation.

Predictive value of flexible proctosigmoidoscopy and laboratory findings for complete clinical responses after neoadjuvant chemoradiotherapy in patients with locally advanced primary rectal cancer: a retrospective cohort study

PURPOSE

Colorectal cancer is the second leading cause of cancer death worldwide. Standard treatments for locally advanced rectal cancer include neoadjuvant chemoradiotherapy and total mesorectal excision (TME), which are associated with significant morbidity. After neoadjuvant therapy, one-third of patients achieve a pathological complete response (pCR) and are eligible for a watch-and-wait approach without TME. The purpose of this study was to determine the potential predictors of pCR before surgery.

METHODS

The demographic, clinical, and endoscopic data of 119 patients with primary locally advanced rectal cancer without distant metastasis who underwent restaging endoscopy and TME 6-8 weeks after the end of neoadjuvant therapy were collected. The absence of tumor cells in the histological examination of the TME specimen after neoadjuvant therapy was considered pCR. Binary logistic regression and receiver operating characteristic curves were utilized for analysis.

RESULTS

According to the multivariate logistic regression analysis, flattening of marginal tumor swelling (p value < 0.001, odds ratio = 100.605) emerged as an independent predictor of pCR in rectal cancer patients. Additionally, receiver operating characteristic curve analysis revealed that lower preoperative carcinoembryonic antigen and erythrocyte sedimentation rate levels predict pCR, with cutoffs of 2.15 ng/ml and 19.0 mm/h, respectively.

CONCLUSION

Carcinoembryonic antigen and erythrocyte sedimentation rate, along with the presence of flattening of marginal tumor swelling, can predict pCR after neoadjuvant chemoradiotherapy in patients with primary rectal cancer. These factors offer a potential method for selecting candidates for conservative treatment based on endoscopic and laboratory findings.

Sense and non-sense of imaging in the era of organ preservation for rectal cancer

This review summarizes the current applications and benefits of imaging modalities for organ preservation in the treatment of rectal cancer. The concept of organ preservation in the treatment of rectal cancer has revolutionized the way rectal cancer is managed. Initially, organ preservation was limited to patients with locally advanced rectal cancer who needed neoadjuvant therapy to reduce tumor size before surgery and achieved complete response. However, neoadjuvant therapy is now increasingly utilized for smaller and less aggressive tumors to achieve primary organ preservation. Additionally, more intensive neoadjuvant strategies are employed to improve complete response rates and increase the chances of successful organ preservation. The selection of patients for organ preservation is a critical component of treatment, and imaging techniques such as digital rectal exam, endoscopy, and MRI are commonly used for this purpose. In this review, we provide an overview of what imaging modalities should be chosen and how they can aid in the selection and follow-up of patients undergoing organ-preserving strategies.

Neoadjuvant chemoradiation therapy combined with immunotherapy for microsatellite stable ultra-low rectal cancer (CHOICE II): study protocol of a multicentre prospective randomised clinical trial

INTRODUCTION

Neoadjuvant chemoradiotherapy (nCRT) could bring tumour shrinking and downstaging and increase the probability of organ preservation for patients with low rectal cancer. But for ultra-low rectal cancer, there is little possibility for organ preservation. Immunotherapy has been shown to have significant survival benefits in microsatellite instability-high patients but poor response in microsatellite stable (MSS) patients. Studies have demonstrated that radiotherapy and immunotherapy have synergistic effects in cancer treatment. There is no existing evidence about the clinical efficacy of immunotherapy combined with nCRT for patients with MSS ultra-low rectal cancer.

METHOD AND ANALYSIS

This trial is an open-labelled multicentre prospective randomised controlled trial (NCT05215379) with two parallel groups and allocation ratio 1:1 (nCRT+immunotherapy vs nCRT group). Eligible participants will be aged 18-75 years, with a desire for anus preservation, confirmed cT1-3aN0-1M0 rectal adenocarcinoma, confirmed MSS type, inferior margin of ≤5 cm from the anal verge. The primary endpoint of this trial is complete clinical response (cCR) rate. Immunotherapy is added after 1 week of chemoradiotherapy for two cycles, and then the patients will be administered two cycles of immunotherapy and CAPOX. The evaluations will be carried out after the completion of the whole neoadjuvant therapy. We expect the programme to improve the cCR rate and the quality of life for patients with ultra-low rectal cancer.

ETHICS AND DISSEMINATION

This trial was approved by the Ethics committee of Changhai Hospital and other medical centres (Grant number:CHEC2022-118). The results of this study will provide further insight into the clinical efficacy of immunotherapy in combination with nCRT in patients with MSS ultra-low rectal cancer.

TRIAL REGISTRATION NUMBER

NCT05215379.

Watch and Wait Approach for Rectal Cancer

The administration of neoadjuvant chemoradiotherapy (nCRT) followed by total mesorrectal excision (TME) and selective use of adjuvant chemotherapy can still be considered the standard of care in locally advanced rectal cancer (LARC). However, avoiding sequelae of TME and entering a narrow follow-up program of watch and wait (W&W), in select cases that achieve a comparable clinical complete response (cCR) to nCRT, is now very attractive to both patients and clinicians. Many advances based on well-designed studies and long-term data coming from big multicenter cohorts have drawn some important conclusions and warnings regarding this strategy. In order to safely implement W&W, it is important consider proper selection of cases, best treatment options, surveillance strategy and the attitudes towards near complete responses or even tumor regrowth. The present review offers a comprehensive overview of W&W strategy from its origins to the most current literature, from a practical point of view focused on daily clinical practice, without losing sight of the most important future prospects in this area.

Optimized tools and timing of response reassessment after neoadjuvant chemoradiation in rectal cancer

PURPOSE

Reassessment tools of response to long-course neoadjuvant chemoradiation treatment (nCRT) in patients with locally advanced rectal cancer (LARC) are important in predicting complete response (CR) and thus deciding whether a wait-and-watch strategy can be implemented in these patients. Choosing which routine reassessment tools are optimal and when to use them is still unclear and will be researched in the study.

METHODS

Altogether, 250 patients with LARC who received nCRT from 2013 to 2021 and were followed up were retrospectively reviewed. Common reassessment tools of response included digital rectal examination (DRE), clinical examination and symptoms, endoscopy, biopsy, magnetic resonance imaging (MRI), and blood biomarkers.

RESULTS

Overall, 27.20% (68/250) patients had a complete response and 72.80% (182/250) did not. The combination of MRI, endoscopy, and biopsy showed the best performance in terms of accuracy of 74% and area under the curve (AUC, 0.714, 95% CI 0.546-0.882). Reassessing through DRE and presence of symptoms failed to improve the efficacy of response reassessment. After 100 days, biopsy as an assessment tool would obtain a substantial rise in accuracy from 51.28 to 100% (p = 0.003).

CONCLUSION

The combination of MRI, endoscopy, and biopsy is suitable as the reassessment tool of response for applying a wait-and-watch strategy after long-course nCRT in patients with LARC. The accuracy of biopsy as reassessment tools would be improved if they were used over 100 days after nCRT in patients with rectal cancer.

A meta-analysis of the watch-and-wait strategy versus total mesorectal excision for rectal cancer exhibiting complete clinical response after neoadjuvant chemoradiotherapy

Background

Some clinical researchers have reported that patients with cCR (clinical complete response) status after neoadjuvant chemoradiotherapy (nCRT) could adopt the watch-and-wait (W&W) strategy. Compared with total mesorectal excision (TME) surgery, the W&W strategy could achieve a similar overall survival. Could the W&W strategy replace TME surgery as the main treatment option for the cCR patients? By using the meta-analysis method, we evaluated the safety and efficacy of the W&W strategy and TME surgery for rectal cancer exhibiting cCR after nCRT.

Methods

We evaluated two treatment strategies for rectal cancer with cCR after nCRT up to July 2021 by searching the Cochrane Library, PubMed, Wanfang, and China National Knowledge Infrastructure (CNKI) databases. Clinical data for primary outcomes (local recurrence, cancer-related death and distant metastasis), and secondary outcomes (disease-free survival (DFS) and overall survival (OS)) were collected to evaluate the efficacy and safety in the two groups.

Results

We included nine studies with 818 patients in the meta-analysis, and there were five moderate-quality studies and four high-quality studies. A total of 339 patients were in the W&W group and 479 patients were in the TME group. The local recurrence rate in the W&W group was greater than that in the TME group in the fixed-effects model (OR 8.54, 95% CI 3.52 to 20.71, P < 0.001). The results of other outcomes were similar in the two groups.

Conclusion

The local recurrence rate of the W&W group was greater than that in the TME group, but other results were similar in the two groups. With the help of physical examination and salvage therapy, the W&W strategy could achieve similar treatment effects with the TME approach.

Trial registration

Protocol registration number: CRD42021244032.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12957-021-02415-y.

Role of 18F-PET-CT to predict pathological response after neoadjuvant treatment of rectal cancer

OBJECTIVES

Neoadjuvant chemoradiation (nCRT) is universally considered to be a valid treatment to achieve downstaging, to improve local disease control and to obtain better resectability in locally advanced rectal cancer (LARC). The aim of this study is to correlate the change in the tumour 18F-FDG PET-CT standardized uptake value (SUV) before and after nCRT, in order to obtain an early prediction of the pathologic response (pR) achieved in patients with LARC.

DATA DESCRIPTION

We performed a retrospective analysis of patients with LARC diagnosis who underwent curative resection. All patients underwent a baseline 18F-FDG PET-CT scan within the week prior to the initiation of the treatment (PET-CT SUV1) and a second scan (PET-CT SUV2) within 6 weeks of the completion of nCRT. We evaluated the prognostic value of 18F-FDG PET-CT in terms of disease-free survival (DFS) and overall survival (OS) in patients with LARC.A total of 133 patients with LARC were included in the study. Patients were divided in two groups according to the TRG (tumour regression grade): 107 (80%) as the responders group (TRG0-TRG1) and 26 (25%) as the no-responders group (TRG2-TRG3). We obtained a significant difference in Δ%SUV between the two different groups; responders versus no-responders (p < 0.012). The results of this analysis show that 18F-FDG PET-CT may be an indicator to evaluate the pR to nCRT in patients with LARC. The decrease in 18F-FDG PET-CT uptake in the primary tumour may offer important information in order for an early identification of those patients more likely to obtain a pCR to nCRT and to predict those who are unlikely to significantly regress.

Predicting pathological response to chemoradiotherapy for rectal cancer: a systematic review

Introduction: Pathological complete response (pCR) rates of approximately 20% following neoadjuvant long-course chemoradiotherapy for rectal cancer have given rise to non-operative or watch-and-wait (W&W) management. To improve outcomes there has been significant research into predictors of response. The goal is to optimize selection for W&W, avoid chemoradiotherapy in those who won't benefit and improve treatment to maximize the clinical complete response (cCR) rate and the number of patients who can be considered for W&W.Areas covered: A systematic review of articles published 2008-2018 and indexed in PubMed, Embase or Medline was performed to identify predictors of pathological response (including pCR and recognized tumor regression grades) to fluoropyrimidine-based chemoradiotherapy in patients who underwent total mesorectal excision for rectal cancer. Evidence for clinical, biomarker and radiological predictors is discussed as well as potential future directions.Expert opinion: Our current ability to predict the response to chemoradiotherapy for rectal cancer is very limited. cCR of 40% has been achieved with total neoadjuvant therapy. If neoadjuvant treatment for rectal cancer continues to improve it is possible that the treatment for rectal cancer may eventually parallel that of anal squamous cell carcinoma, with surgery reserved for the minority of patients who don't respond to chemoradiotherapy.

Nonoperative Management for T2 Low Rectal Cancer: A Western Approach

The possibility of organ preservation in early rectal cancer has gained popularity during recent years. Patients with early tumor stage and low risk for local recurrence do not usually require neoadjuvant chemoradiation for oncological reasons. However, these patients may be considered for chemoradiation exclusively for the purpose of achieving a complete clinical response and avoid total mesorectal excision. In addition, cT2 tumors may be more likely to develop complete response to neoadjuvant therapy and may constitute ideal candidates for organ-preserving strategies. In the setting where the use of chemoradiation is exclusively used to avoid major surgery, one should consider maximizing tumor response. In this article, we will focus on the rationale, indications, and outcomes of patients with early rectal cancer being treated by neoadjuvant chemoradiation to achieve organ preservation by avoiding total mesorectal excision.

Assessing tumor response to neoadjuvant chemoradiation in rectal cancer with rectoscopy and 18F-FDG PET/CT: results from a prospective series

INTRODUCTION

rectoscopy and 18F-FDG PET/CT as a diagnostic algorithm for the assessment of tumor response in rectal cancer after neoadjuvant chemoradiation therapy (CRT) is very useful.

MATERIAL AND METHODS

this was a prospective longitudinal study in patients with locally advanced rectal cancer treated with neoadjuvant CRT. Patients were assessed after CRT completion with a digital rectal examination, proctoscopy and 18F-FDG PET/CT. Patients were subdivided as clinical (cCR) or radiologic (rCR) responders and non-responders according to tumor response. Clinical and radiological re-assessment was compared with the surgical specimen. Pathological tumor regression (pCR) grade was determined according to Mandard's classification. Of the 68 patients included, 15 (22 %) presented pCR in the surgical specimen and tumor persistence (non-PCR) was detected in the remaining 53 (78 %). Clinical assessment (DRE+ rectoscopy) identified 15 patients as cCR and 53 as non-cCR, two were false positives and two were false negatives. The overall accuracy was 94 %. 18F-FDG PET/CT identified 18 patients as rCR and 50 as non-rCR, one was a false positive and four were false negatives. The overall accuracy was 92 %. A combination of clinical findings and 18F-FDG PET/CT resulted in an accuracy of 96 %. The combination of clinical findings + 18F-FDG PET/CT was able to correctly identify all cases of pCR, with the exception of one case that presented a tumor regression of 80 %. In this series, 18F-PET-CT and clinical assessment had excellent accuracies in differentiating PCR from non-PCR after CRT completion. PET-CT combined with clinical assessment had a better accuracy than both modalities independently. 18F-FDG PET/CT is a valid tool that complements the clinical assessment of tumor response.

The Role of Micro-RNAs and Circulating Tumor Markers as Predictors of Response to Neoadjuvant Therapy in Locally Advanced Rectal Cancer

The response to neoadjuvant chemoradiation (nCRT) is a critical step in the management of locally advanced rectal cancer (LARC) patients. Only a minority of LARC patients responds completely to neoadjuvant treatments, thus avoiding invasive radical surgical resection. Moreover, toxic side effects can adversely affect patients' survival. The difficulty in separating in advances responder from non-responder patients affected by LARC highlights the need for valid biomarkers that guide clinical decision-making. In this context, microRNAs (miRNAs) seem to be promising candidates for predicting LARC prognosis and/or therapy response, particularly due to their stability, facile detection, and disease-specific expression in human tissues, blood, serum, or urine. Although a considerable number of studies involving potential miRNA predictors to nCRT have been conducted over the years, to date, the identification of the perfect miRNA signatures or single miRNA, as well as their use in the clinical practice, is still representing a challenge for the management of LARC patients. In this review, we will first introduce LARC and its difficult management. Then, we will trace the scientific history and the key obstacles for the identification of specific miRNAs that predict responsiveness to nCRT. There is a high potential to identify non-invasive biomarkers that circulate in the human bloodstream and that might indicate the LARC patients who benefit from the watch-and-wait approach. For this, we will critically evaluate recent advances dealing with cell-free nucleic acids including miRNAs and circulating tumor cells as prognostic or predictive biomarkers.

Controversies in Rectal Cancer Treatment and Management

Incorporation of new treatment modalities has significantly increased the complexity of the treatment and management of rectal cancer, including perioperative therapy for local advanced disease and organ preservation for those with response to the preoperative treatment. This review may help practitioners better understand the rationale and selection.

Organ Preservation in cT2N0 Rectal Cancer After Neoadjuvant Chemoradiation Therapy: The Impact of Radiation Therapy Dose-escalation and Consolidation Chemotherapy

OBJECTIVE

To demonstrate the difference in organ-preservation rates and avoidance of definitive surgery among cT2N0 rectal cancer patients undergoing 2 different chemoradiation (CRT) regimens.

BACKGROUND

Patients with cT2N0 rectal cancer are more likely to develop complete response to neoadjuvant CRT. Organ preservation has been considered an alternative treatment strategy for selected patients. Radiation dose-escalation and consolidation chemotherapy have been associated with increased rates of response and may improve chances of organ preservation among these patients.

METHODS

Patients with distal and nonmetastatic cT2N0 rectal cancer managed by neoadjuvant CRT were retrospectively reviewed. Patients undergoing standard CRT (50.4 Gy and 2 cycles of 5-FU-based chemotherapy) were compared with those undergoing extended CRT (54 Gy and 6 cycles of 5-FU-based chemotherapy). Patients were assessed for tumor response at 8 to 10 weeks. Patients with complete clinical response (cCR) underwent organ-preservation strategy ("Watch and Wait"). Patients were referred to salvage surgery in the event of local recurrence during follow-up.

RESULTS

Thirty-five patients underwent standard and 46 patients extended CRT. Patients undergoing extended CRT were more likely to undergo organ preservation and avoid definitive surgical resection at 5years (67% vs 30%; P = 0.001). After development of a cCR, surgery-free survival is similar between extended and standard CRT groups at 5 years (78% vs 56%; P = 0.12).

CONCLUSIONS

Dose-escalation and consolidation chemotherapy leads to increased long-term organ-preservation rates among cT2N0 rectal cancer. After achievement of a cCR, the risk for local recurrence and need for salvage surgery is similar, irrespective of the CRT regimen.

"Watch and Wait" for complete clinical response after neoadjuvant chemoradiotherapy for rectal cancer

The management of rectal cancer has evolved substantially over recent decades, becoming increasingly complex. This was once a disease associated with high mortality and limited treatment options that typically necessitated a permanent colostomy, has now become a model for multidisciplinary evaluation, treatment and surgical advancement. Despite advances in the rates of total mesorectal excision, decreased local recurrence and increased 5-year survival rates, the multimodal treatment of rectal cancer is associated with a significant impact on long-term functional and quality of life outcomes including risks of bowel, bladder and sexual dysfunction, and potential need for a permanent stoma. There is great interest in strategies to decrease the toxicity of treatment, including selective use of radiation, chemotherapy or even surgery. The modern concept of selective use of surgery for patients with rectal cancer are based on the observed pathological complete response in approximately 10-20% of patients following long-course chemoradiation therapy. While definitive surgical resection remains the standard of care for all patients with non-metastatic rectal cancer, a growing number of studies are providing supportive evidence for a watch-and-wait, organ preserving approach in highly selected patients with rectal cancer. However, questions regarding the heterogeneity of patient selection, optimal method for inducing pathological complete response, methods and intervals for assessing treatment response and adequacy of follow-up remain unanswered. The aim of this review is to provide an up-to-date summary of the current evidence for the watch-and-wait management of rectal cancer following a complete clinical response after neoadjuvant chemoradiation.

Oncological and Survival Outcomes in Watch and Wait Patients With a Clinical Complete Response After Neoadjuvant Chemoradiotherapy for Rectal Cancer: A Systematic Review and Pooled Analysis

OBJECTIVE

The aim of this study was to evaluate the oncological and survival outcomes of a Watch and Wait policy in rectal cancer after a clinical complete response (cCR) following neoadjuvant chemoradiotherapy.

BACKGROUND

The detection of a cCR after neoadjuvant treatment may facilitate a nonoperative approach in selected patients. However, the long-term safety of this strategy remains to be validated.

METHOD

This is a systematic review of the literature to determine the oncological outcomes in Watch and Wait patients. The primary outcome was the cumulative rate of local regrowth, success of salvage surgery, and incidence of metastases. We also evaluated survival outcomes. A pooled analysis of manually extracted summary statistics from individual studies was carried out using inverse variance weighting.

RESULTS

Seventeen studies comprising 692 patients were identified; incidence of cCR was 22.4% [95% confidence interval (CI),14.3-31.8]. There were 153 (22.1%) local regrowths, of which 96% (n = 147/153) manifested in the first 3 years of surveillance. The 3-year cumulative risk of local regrowth was 21.6% (95% CI, 16.0-27.8). Salvage surgery was performed in 88% of patients, of which 121 (93%) had a complete (R0) resection. Fifty-seven metastases (8.2%) were detected, and 35 (60%) were isolated without evidence of synchronous regrowths; 3-year incidence was 6.8% (95% CI, 4.1-10.2). The 3-year overall survival was 93.5% (95% CI, 90.2-96.2).

CONCLUSION

In rectal cancer patients with a cCR following neoadjuvant chemoradiotherapy, a Watch and Wait policy appears feasible and safe. Robust surveillance with early detection of regrowths allows a high rate of successful salvage surgery, without an increase in the risk of systemic disease, or adverse survival outcomes.

The impact of total neo-adjuvant treatment on nonoperative management in patients with locally advanced rectal cancer: The evaluation of 66 cases

BACKGROUND

The study aimed to assess if adherence to a total-neoadjuvant-treatment (TNT) protocol followed by observation(watch-and-wait) led to the successful nonoperative-management of low-rectal-cancer.

METHODS

In this study, patients with primary, resectable-T3-T4, N0-N1 distal-rectal-adenocarcinoma underwent-chemoradiotherapy + consolidation-chemotherapy (TNT). During the-TNT-period, endoscopy, MRI, and FDG-PET/CT were performed. We allocated patients with complete-clinical-tumor-regression, who underwent endoscopy every two months, MRI every-four-months, and PET/CT every-six-months-after-treatment, to the observation-group(OG). All other patients were referred for surgery. The OG was followed-up. The primary endpoint was local tumor-ecurrence after allocation to the OG.

RESULTS

Between 2015 and 2018, we enrolled 66-patients. Of 60-patients who were eligible to participate, 39 had complete-clinical-response(cCR) and were allocated to the OG, six underwent local-excision (LE), and 15 underwent total-mesorectal-excision (TME). The median follow-up duration was 22 (9-42) months. The local-recurrence-rate in the OG was 15.3%, and the LE and TME rates were 16.6% and 0%, respectively. All recurrence cases were salvaged through either LE or TME. The-distant-metastasis rate was 5.1%, 16.6%, and 12.5% in the OG, LE, and TME groups, respectively. The endoscopic negative-predictive-value(NPV) was 50%, and the positive-predictive-value(PPV) was 76.9% in the surgery group (LE + TME). MRI; NPV-50%, PPV-76.9%. PET/CT; NPV-100%, PPV-93.3%. Six patients(28.57%) from surgery group achieved complete pathological response (cPR).

CONCLUSION

Our results indicated a high proportion of selected-rectal-cancers with-cCR after neo-adjuvant-therapy could potentially be managed non-operatively, and major surgery may be avoided.

Impact of PET/CT for Restaging Patients With Locally Advanced Rectal Cancer After Neoadjuvant Chemoradiation

BACKGROUND

A major challenge in identifying candidates for nonoperative management of locally advanced rectal cancer is predicting pathologic complete response (pCR) following chemoradiation. We evaluated pre- and post-CRT PET-CT imaging to predict pCR and prognosis in this set of patients undergoing resection after neoadjuvant therapy.

METHODS

We retrospectively identified patients from 2002 to 2015 with locally advanced rectal cancer who underwent CRT, pre- and post-CRT PET-CT imaging, and resection. Univariate and multivariate analysis was performed and receiver operating characteristic (ROC) curves were generated to evaluate the association of PET-CT characteristics with pCR and survival. ROC curves were generated to define optimal cutoff points for predictive PET-CT characteristics.

RESULTS

125 patients were included. pCR rate was 28%, and follow-up was 48 mo. On multivariable analysis, patients who had a pCR had lower median post-CRT maximal standardized uptake value (SUV_max) (3.2 versus 5.2, P = 0.009) and higher median %SUV decrease (72 versus 58%, P = 0.009). ROC curves were generated for %SUV_max decrease (AUC = 0.70) and post-CRT SUV (AUC = 0.69). Post-CRT SUV_max <4.3 and %SUV_max decrease of >66% were equally predictive of pCR with a sensitivity of 65%, specificity of 72%, PPV of 44%, and NPV of 86%. Median 5-y overall and relapse-free survival were improved for patients with post-CRT SUV <4.3 (OS: 86 versus 66%, P = 0.01; RFS: 75 versus 52%, P = 0.01) or %SUV decrease of >66% (OS, 82 versus 66%, P = 0.05; RFS, 75 versus 54%, P = 0.01).

CONCLUSIONS

PET/CT may be useful in identifying patients who did not achieve pCR, as well as overall survival in patients undergoing CRT for rectal cancer. Patients with a post-CRT SUV of >4.3 should be considered for operative management, as an estimated 86% of these patients will not have a pCR.

Organ Preservation Strategies After Neoadjuvant Chemoradiotherapy for Locally Advanced Rectal Cancer

Standard use of neoadjuvant chemoradiotherapy, total mesorectal excision, and postoperative adjuvant chemotherapy in locally advanced rectal cancer has tremendously improved oncologic outcomes over the past several decades. However, these improvements come with costs of significant morbidity and poor quality of life. Along with developments in imaging techniques, clinical experience and evidence have identified a certain subgroup of patients that have exceptionally good clinical outcomes while preserving quality of life. Driven by patient demand and interest in preserving quality of life, numerous organ preservation treatment strategies for managing rectal cancer are rapidly evolving. Herein, the flow of research in organ preservation strategies and counter arguments are discussed.

Clinical and molecular diagnosis of pathologic complete response in rectal cancer: an update

INTRODUCTION

The standard of care for locally advanced rectal cancer includes neoadjuvant chemoradiation with subsequent total mesorectal excision. This approach has shown various degrees of response to neoadjuvant chemoradiation (ranging from complete response to further tumor growth), which have substantial prognostic and therapeutic implications. A total regression of the tumor is a predictor of superior oncologic outcomes compared with partial responders and non-responders. Further, this concept has opened the possibility of nonoperative strategies for complete responders and explains the widespread research interest in finding clinical, radiographic, pathologic, and biochemical parameters that allow for identification of these patients. Areas covered: The present review evaluates the most recent efforts in the literature to identify predictors of patients likely to achieve a complete response following neoadjuvant treatment for the management of rectal cancer. This includes clinical predictors of pathologic complete response such as tumor location, size, and stage, molecular predictors such as tumor biology and microRNA, serum biomarkers such as carcinoembryogenic antigen and nomograms. Expert commentary: There has been significant progress in our ability to predict pathological complete response. However, more high-quality research is still needed to use this concept to confidently dictate clinical management.

Session 4: Trying to augment response with chemotherapy: a triumph of hope over experience?

As part of an approach to improve tumour regression and increase the proportion of patients with complete clinical and radiological response, Dr Perez reviews the methods and evidence base for augmenting therapy and thus augmenting response rates preoperatively. Much of the data reviewed were in the context of patients undergoing a watch-and-wait approach for rectal cancer after initial treatment with chemoradiotherapy.

Development and validation of an MRI-based model to predict response to chemoradiotherapy for rectal cancer

BACKGROUND AND PURPOSE

To safely implement organ preserving treatment strategies for patients with rectal cancer, well-considered selection of patients with favourable response is needed. In this study, we develop and validate an MRI-based response predicting model.

METHODS

A multivariate model using T2-volumetric and DWI parameters before and 6 weeks after chemoradiation (CRT) was developed using a cohort of 85 rectal cancer patients and validated in an external cohort of 55 patients that underwent preoperative CRT.

RESULTS

Twenty-two patients (26%) achieved ypT0-1N0 response in the development cohort versus 13 patients (24%) in the validation cohort. Two T2-volumetric parameters (ΔVolume% and Sphere_post) and two DWI parameters (ADC_avg_post and ADCratio_avg) were retained in a model predicting (near-)complete response (ypT0-1N0). In the development cohort, this model had a good predictive performance (AUC = 0.89; 95% CI 0.80-0.98). Validation of the model in an external cohort resulted in a similar performance (AUC = 0.88 95% CI 0.79-0.98).

CONCLUSION

An MRI-based prediction model of (near-)complete pathological response following CRT in rectal cancer patients, shows a high predictive performance in an external validation cohort. The clinically relevant features in the model make it an interesting tool for implementation of organ-preserving strategies in rectal cancer.

Baseline T Classification Predicts Early Tumor Regrowth After Nonoperative Management in Distal Rectal Cancer After Extended Neoadjuvant Chemoradiation and Initial Complete Clinical Response

BACKGROUND

Selected patients with rectal cancer and complete clinical response after neoadjuvant chemoradiation have been managed nonoperatively with acceptable outcomes. However, ≈20% of these patients will develop early tumor regrowth. Identification of these patients could select candidates for more intensive follow-up.

OBJECTIVE

The purpose of this study was to investigate the influence of baseline radiological T classification on recurrences after a complete clinical response managed nonoperatively after chemoradiation.

DESIGN

This was a retrospective review of a prospective collected database.

SETTINGS

The study was conducted at a single center.

PATIENTS

Patients with distal rectal cancer (cT2-4N0-2M0) undergoing extended chemoradiation (54 Gy + 5-fluorouracil-based chemotherapy) were eligible. Patients were reassessed for tumor response at 10 weeks after radiation completion. Patients with complete clinical response (clinical, radiological, and endoscopic) were managed nonoperatively and strictly followed.

MAIN OUTCOMES MEASURES

Complete clinical response rates, early tumor regrowth rates (<12 mo), local recurrence-free survival, and distant metastases-free survival were measured.

RESULTS

A total of 91 consecutive patients with rectal cancer underwent extended chemoradiation. Sixty-one patients developed initial complete clinical response (67%). cT2 patients developed similar initial complete clinical response rates compared with cT3/T4 (72% vs 63%; p = 0.403). Early tumor regrowths were more frequent among baseline cT3/4 when compared with cT2 patients (30% vs 3%; p = 0.007). There were no differences in late local recurrences (p = 0.593) or systemic recurrences (p = 0.387). Local recurrence-free survival was significantly better for cT2 patients at 1 year (96% vs 69%; p = 0.009). After Cox regression analysis, baseline T stage was an independent predictor of improved local recurrence-free survival at 1 year (p = 0.03; OR = 0.09 (95% CI, 0.01-0.81)).

LIMITATIONS

This study was limited by its small sample size, retrospective nature, and short follow-up.

CONCLUSIONS

cT2 patients who develop complete clinical response after extended chemoradiation managed nonoperatively are less likely to develop early tumor regrowths when compared with cT3/4 patients. cT3/4 patients should undergo more intensive follow-up after a complete clinical response to allow for early detection of early regrowths.

Semiquantitative Volumetry by Sequential PET/CT May Improve Prediction of Complete Response to Neoadjuvant Chemoradiation in Patients With Distal Rectal Cancer

BACKGROUND

Previous studies using PET/CT imaging have failed to accurately identify complete responders to neoadjuvant chemoradiation among patients with rectal cancer. The use of metabolic parameters alone or imprecise delineation of baseline and residual tumor volumes may have contributed for these disappointing findings.

OBJECTIVE

The purpose of this study was to determine the accuracy of complete response identification in rectal cancer after neoadjuvant chemoradiation by sequential PET/CT imaging with a decrease in tumor metabolism and volume using optimal tumor volume delineation.

DESIGN

This was a retrospective comparison of prospectively collected data from a clinical trial (National Clinical Trial 00254683).

SETTINGS

The study was conducted at a single research center.

PATIENTS

Ninety patients with cT2-4N0-2M0 distal rectal cancer underwent sequential PET/CT at baseline and 12 weeks after neoadjuvant chemoradiation. Quantitative metabolic analysis (median and maximal standard uptake values), volumetric estimates (metabolic tumor volume), and composite estimates incorporating volume and quantitative data (total lesion glycolysis) were compared for the assessment of response to neoadjuvant chemoradiation using receiver operating characteristic curves. Individual standard uptake value thresholds were used according to response to neoadjuvant chemoradiation to match metabolic activity and optimize volume delineation.

MAIN OUTCOME MEASURES

The accuracy of complete response identification by multiple volumetric and metabolic parameters using sequential PET/CT imaging was measured.

RESULTS

Variation in total lesion glycolysis between baseline and 12-week PET/CT scans was associated with the best area under the curve (area under the curve = 0.81 (95% CI, 0.69-0.92)) when compared with standard uptake value or metabolic tumor volume for the identification of a complete responder. Patients with a ≥92% decrease in total lesion glycolysis between baseline and 12-week PET/CT scan had a 90% chance to harbor complete response.

LIMITATIONS

This study was limited by its lack of interobserver agreement analysis.

CONCLUSIONS

PET/CT scan using volume and metabolic estimates with individual standard uptake value thresholds for volume determination may provide a useful tool to predict response to neoadjuvant chemoradiation in distal rectal cancer.

Prediction of tumor response after neoadjuvant chemoradiotherapy in rectal cancer using (18)fluorine-2-deoxy-D-glucose positron emission tomography-computed tomography and serum carcinoembryonic antigen: a prospective study

PURPOSE

To investigate the association between (18)fluorine-2-deoxy-D-glucose positron emission tomography-computed tomography ((18)F-FDG PET/CT) parameters, serum carcinoembryonic antigen (CEA), and tumor response in patients with rectal cancer receiving neoadjuvant chemoradiotherapy (nCRT).

METHODS

Sixty-four patients with T3-4 and/or node-positive rectal cancer receiving nCRT followed by surgery were prospectively studied. PET/CT was performed before, and in 28 patients, both before and after nCRT. The pre-/post-nCRT maximum standardized uptake (SUVmax) values, differences between pre-/post-nCRT SUVmax (∆SUVmax), response index of SUVmax (RI-SUVmax), mean standardized uptake value (SUVmean), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and CEA were measured. The ability of PET/CT parameters and CEA to predict Mandard's tumor regression grade (TRG) and pathological complete remission (pCR) were evaluated.

RESULTS

31 patients were identified as responders (TRG 1-2), and 19 exhibited pCR. For responders, significant differences were found for ΔSUVmax (24.88 vs. 15.39 g/ml, p = 0.037), RI-SUVmax (0.76 vs. 0.63, p = 0.025), ΔSUVmean (14.43 vs. 8.65 g/ml, p = 0.029), RI-SUVmean (0.77 vs. 0.63, p = 0.011), CEA-pre (6.30 vs. 27.86 μg/L, p < 0.001), CEA-post (2.22 vs. 5.49 μg/L, p = 0.002), ΔCEA (4.08 vs. 23.13 μg/L, p < 0.001), and RI-CEA (0.25 vs. 0.55, p = 0.002). Differences between pCR and non-pCR patients were noted as RI-SUVmean (0.77 vs. 0.65, p = 0.043), MTV-pre (9.87 vs. 14.62 cm(3), p = 0.045), CEA-pre (5.62 vs. 22.27 μg/L, p = 0.002), CEA-post (1.95 vs. 4.72 μg/L, p = 0.001), and ΔCEA (3.68 vs. 17.99 μg/L, p = 0.013). Receiver operating characteristic analysis revealed that RI-SUVmean exhibited the greatest accuracy in predicting responders, whereas CEA-post and ΔCEA exhibited the greatest accuracy in predicting pCR.

CONCLUSIONS

(18)F-FDG PET/CT parameters and CEA are accurate tools for predicting tumor response to nCRT in rectal cancer.

Consolidation chemotherapy during neoadjuvant chemoradiation (CRT) for distal rectal cancer leads to sustained decrease in tumor metabolism when compared to standard CRT regimen

Background

Neoadjuvant CRT may lead to significant tumor regression in patients with rectal cancer. Different CRT regimens with consolidation chemotherapy may lead to increased rates of complete tumor regression. The purpose of this study was to understand tumor metabolic activity following two different neoadjuvant CRT regimens using sequential PET/CT imaging in two different intervals following RT.

Methods

Patients with cT2-4 N0-2 M0 rectal cancer treated by standard CRT (54Gy and 2 cycles of 5FU-based chemotherapy) or extended CRT (54Gy and 6 cycles of 5FU-based chemotherapy) underwent sequential PET/CT imaging at baseline, 6 weeks and 12 weeks from radiation completion.

Results

99 patients undergoing standard CRT were compared to 12 patients undergoing CRT with consolidation chemotherapy. Patients treated with consolidation CRT had increased rates of complete clinical or pathological response (66 % vs. 23 %; p < 0.001). SUVmax variation between baseline and 6 weeks (88 % vs. 63 %; p < 0.001) and between baseline and 12 weeks (90 % vs. 57 %; p < 0.001) were significantly more pronounced among patients undergoing extended CRT with consolidation chemotherapy. An increase in SUVmax between 6 and 12 weeks was observed in 51 % of patients undergoing standard and 18 % of patients undergoing consolidation CRT (p = 0.04).

Conclusions

Most of the reduction in tumor metabolism after neoadjuvant CRT occurs within the first 6 weeks from RT completion. In patients undergoing CRT with consolidation chemotherapy, tumors are less likely to regain metabolic activity between 6 and 12 weeks. Therefore, assessment of tumor response may be safely postponed to 12 weeks in patients undergoing extended CRT with consolidation chemotherapy.

Trial registration

NCT00254683

The role of diffusion-weighted MRI and (18)F-FDG PET/CT in the prediction of pathologic complete response after radiochemotherapy for rectal cancer: a systematic review

After neoadjuvant radiochemotherapy (RCT) for locally advanced rectal cancer, 15-27% of the patients experience a pathological complete response (pCR). This observation raises the question as to whether invasive surgery could be avoided in a selected cohort of patients who obtain a clinical complete response after preoperative RCT. In this respect, there has been growing interest in functional imaging techniques to improve clinical response assessment. This systematic review focuses on the role of diffusion-weighted imaging (DWI) and (18)F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) in the prediction of pCR after RCT for rectal cancer. A total of 14 publications on DWI and 25 on (18)F-FDG PET/CT were retrieved. Pooled analysis of individual patient data shows both imaging modalities have a low positive predictive value in the prediction of pCR (mean PPV of 54% and 39% for DWI- and (18)F-FDG PET/CT-based parameters respectively). Especially pre-RCT imaging is unable to predict pCR with overall accuracies of 68-72% for DWI and 44% for (18)F-FDG PET/CT. Qualitative DWI assessment 5-10weeks after the end of RCT may outperform apparent diffusion coefficient (ADC)-based DWI-parameters (overall accuracy of 87% vs. 74-78%). Although few data are available, early changes in FDG-uptake seem promising in the prediction of pCR and the role of (18)F-FDG PET/CT during RCT should be further investigated. Quantitative and qualitative (18)F-FDG PET/CT measurements are equally effective in the assessment of pCR after RCT. The major strength of DWI and (18)F-FDG PET/CT lies in the identification of non-responders who are not candidates for organ preservation. Up to now, DWI and (18)F-FDG PET/CT are not accurate enough to safely select patients for organ-sparing strategies. Future research must focus on the integration of functional imaging with clinical data and molecular biomarkers.

Comparison of (18)F-FDG PET/CT methods of analysis for predicting response to neoadjuvant chemoradiation therapy in patients with locally advanced low rectal cancer

PURPOSE

The aim of this study was to prospectively investigate the predictive value of (18)F-FDG PET/CT semiquantitative parameters for locally advanced low rectal cancer (LARC) treated by neoadjuvant chemoradiation therapy (nCRT).

METHODS

68 patients with LARC had (18)F-FDG PET/CT scans twice (baseline and 5-6 weeks post-nCRT). All patients underwent surgery with preservation of the sphincter 8 weeks later. (18)F-FDG PET/CT analysis was performed by visual response assessment (VRA) and semiquantitative parameters: SUVmax(baseline), SUVmean(baseline), MTV(baseline), TLG(baseline), SUVmax(post-nCRT), SUVmean(post-nCRT), MTV(post-nCRT), TLG(post-nCRT); ΔSUVmax and mean and Response indexes (RImax% and RImean%). Assessment of nCRT tumor response was performed according to the Mandard's Tumor Regression Grade (TRG) and (y)pTNM staging on the surgical specimens. Concordances of VRA with TRG, and with (y)pTNM criteria were evaluated by Cohen's K. Results were compared by t student test for unpaired groups. ROC curve analysis was performed.

RESULTS

VRA analysis of post-nCRT (18)F-FDG PET/CT scan for the (y)pTNM outcome showed sensitivity, specificity, accuracy, PPV, and NPV of 87.5%, 66.7%, 83.8%, 92.5%, and 53.3%, respectively. Concordances of VRA with TRG and with (y)pTNM were moderate. For the outcome variable TRG, the statistical difference between responders and non-responders was significant for SUVmax(post-nCRT) and RImean%; for the outcome variable (y)pTNM, there was a significant difference for MTV(baseline), SUVmax(post-nCRT), SUVmean(post-nCRT), MTV(post-nCRT), RImax%, and RImean%. ROC analysis showed better AUCs: for the outcome variable TRG for SUVmax(post-nCRT), SUVmean(post-nCRT), and RImean%; for the outcome variable (y)pTNM for MTVbaseline, SUVmax(post-nCRT), SUVmean(post-nCRT), MTV(post-nCRT), RImax%, and RImean%. No significant differences among parameters were found.

CONCLUSIONS

Qualitative and semiquantitative evaluations for (18)F-FDG PET/CT are the optimal approach; a valid parameter for response prediction has still to be established.