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

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.

Executive Summary of the American Radium Society on Appropriate Use Criteria for Nonoperative Management of Rectal Adenocarcinoma: Systematic Review and Guidelines

For patients with rectal cancer, the standard approach of chemotherapy, radiation therapy, and surgery (trimodality therapy) is associated with significant long-term toxicity and/or colostomy for most patients. Patient options focused on quality of life (QOL) have dramatically improved, but there remains limited guidance regarding comparative effectiveness. This systematic review and associated guidelines evaluate how various treatment strategies compare to each other in terms of oncologic outcomes and QOL. Cochrane and Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) methodology were used to search for prospective and retrospective trials and meta-analyses of adequate quality within the Ovid Medline database between January 1, 2012, and June 15, 2023. These studies informed the expert panel, which rated the appropriateness of various treatments in 6 clinical scenarios through a well-established consensus methodology (modified Delphi). The search process yielded 197 articles that advised voting. Increasing data have shown that nonoperative management (NOM) and primary surgery result in QOL benefits noted over trimodality therapy without detriment to oncologic outcomes. For patients with rectal cancer for whom total mesorectal excision would result in permanent colostomy or inadequate bowel continence, NOM was strongly recommended as usually appropriate. Restaging with tumor response assessment approximately 8 to 12 weeks after completion of radiation therapy/chemoradiation therapy was deemed a necessary component of NOM. The panel recommended active surveillance in the setting of a near-complete or complete response. In the setting of NOM, 54 to 56 Gy in 27 to 31 fractions concurrent with chemotherapy and followed by consolidation chemotherapy was recommended. The panel strongly recommends primary surgery as usually appropriate for a T3N0 high rectal tumor for which low anterior resection and adequate bowel function is possible, with adjuvant chemotherapy considered if N+. Recent data support NOM and primary surgery as important options that should be offered to eligible patients. Considering the complexity of multidisciplinary management, patients should be discussed in a multidisciplinary setting, and therapy should be tailored to individual patient goals/values.

Oncological risks associated with the planned watch-and-wait strategy using total neoadjuvant treatment for rectal cancer: A narrative review

Overall survival benefit of total neoadjuvant treatment (TNT) remains unconfirmed. Thus, in our opinion, the main rationale for using TNT is a planned watch-and-wait (w&w) strategy to improve patients' long-term quality of life through organ preservation. The OPRA randomized trial, which examined a planned w&w strategy using TNT, showed a higher organ preservation rate but also a higher regrowth rate compared to studies on the opportunistic w&w strategy. Higher rates of complete clinical response with TNT did not improve disease-free survival compared to historical controls. Therefore, the gain in organ-sparing capability might not be balanced by the increased oncological risk. The ultimate local failure rate in the intention-to-treat analysis of the OPRA trial was 13% for induction chemotherapy and 16% for consolidation chemotherapy, which seems higher than expected compared to 8% in a meta-analysis of w&w studies or 12% after TNT and surgery in the PRODIGE-23 and RAPIDO trials, which enrolled patients with more advanced cancers than the OPRA trial. Other studies also suggest worse local control when surgery is delayed for radio-chemoresistant cancers. Our review questions the safety of the planned w&w strategy using TNT in unselected patients. To reduce the oncological risk while maintaining high organ preservation rates, we suggest that the planned w&w strategy using TNT requires a two-tier patient selection process: before treatment and after tumor response assessment at the midpoint of consolidation chemotherapy. These robust selections should identify patients who are unlikely to achieve organ preservation with TNT and would be better managed by preoperative chemoradiotherapy (without consolidation chemotherapy) and surgery, or by discontinuing consolidation chemotherapy and proceeding directly to surgery.

Clinical and genetic factors associated with tumor response to neoadjuvant (chemo)radiotherapy, survival and recurrence risk in rectal cancer

Rectal cancer poses challenges in preoperative treatment response, with up to 30% achieving a complete response (CR). Personalized treatment relies on accurate identification of responders at diagnosis. This study aimed to unravel CR determinants, overall survival (OS), and time to recurrence (TTR) using clinical and targeted sequencing data. Analyzing 402 patients undergoing preoperative treatment, tumor stage, size, and treatment emerged as robust response predictors. CR rates were higher in smaller, early-stage, and intensively treated tumors. Targeted sequencing analyzed 216 cases, while 120 patients provided hotspot mutation data. KRAS mutation dramatically reduced CR odds by over 50% (odds ratio [OR] = 0.3 in the targeted sequencing and OR = 0.4 hotspot cohorts, respectively). In contrast, SMAD4 and SYNE1 mutations were associated with higher CR rates (OR = 6.0 and 6.8, respectively). Favorable OS was linked to younger age, CR, and low baseline carcinoembryonic antigen levels. Notably, CR and an APC mutation increased TTR, while a BRAF mutation negatively affected TTR. Beyond tumor burden, SMAD4 and SYNE1 mutations significantly influenced CR. KRAS mutations independently correlated with radiotherapy resistance, and BRAF mutations heightened recurrence risk. Intriguingly, non-responding tumors with initially small sizes carried a higher risk of recurrence. The findings, even if limited in addition to the imperfect clinical factors, offer insights into rectal cancer treatment response, guiding personalized therapeutic strategies. By uncovering factors impacting CR, OS, and TTR, this study underscores the importance of tailored approaches for rectal cancer patients. These findings, based on extensive analysis and mutation data, pave the way for personalized interventions, optimizing outcomes in the challenges of rectal cancer preoperative treatment.

Significance of Nutritional-Inflammatory Index as Predictors for Total Neoadjuvant Therapy-Induced Tumor Regression in Locally Advanced Rectal Cancer Patients

Purpose

To evaluate the predictive capacity of the nutritional-inflammatory index and clinicopathological characteristics in patients with locally advanced rectal cancer (LARC) receiving total neoadjuvant therapy (TNT).

Methods

Data from 127 patients with LARC receiving TNT from January 2017 to January 2021 were retrospectively analyzed. Clinicopathological characteristics with different TNT-induced responses were compared. The Chi-square test and the Mann-Whitney test were used to analyze the association between pre-TNT factors and TNT-induced responses. Multivariable logistic regression analysis was used to construct a predictive model.

Results

In the cohort of 127 patients with LARC who underwent total neoadjuvant therapy (TNT), the mean age was 54.1 ± 11.4 years; 88 (69.3%) were male. Seventy patients (55.1%) exhibited a favorable response to TNT, while 57 patients (44.9%) demonstrated a poor response. Tumor characteristics, including diameter, distance from the anal verge, pre-TNT lymphocyte, pre-TNT hemoglobin, CA199, PLR, and HALP, exhibit correlations with TNT-induced tumor regression. Multivariate logistic regression analysis identified large tumor diameters (> 5.0 cm; p = 0.005, HR 2.958; 95% CI 1.382-6.335) and low HALP (≤ 40; p = 0.002, HR 0.261; 95% CI 0.111-0.612) as predictors of TNT-induced poor responses. Additionally, low levels of HALP were associated with an increased risk of recurrence in patients with LARC with TNT, but this was not statistically significant (p = 0.087, HR 2.008, 95% CI 0.906-4.447).

Conclusion

A large tumor diameter and low HALP predict poor tumor regression induced by the CAPOX-based TNT regimen in patients with LARC.

Prediction of pathologic complete response to neoadjuvant chemoradiation in locally advanced rectal cancer

Purpose

To investigate the predictive factors of pathologic complete response (pCR) in locally advanced rectal cancer (LARC) patients who had been treated with neoadjuvant chemoradiation (nCRT).

Methods and materials

For this retrospective study, 53 LARC patients (37 males and 16 females; age range 25 to 79 years) were selected. Clinical characteristics, baseline mrTNM staging, MR gross tumor volumes (GTV), and pCR were evaluated. The diagnostic accuracy of GTV for predicting pCR was calculated.

Results

Among 53 LARC patients, 15 patients achieved pCR (28.3%), while 38 patients achieved non-pCR. Only three (5.7%) out of 53 patients did not downstage after nCRT. GTV and tumor differentiation were the significant prognostic parameters for predicting pCR. A tumor volume threshold of 21.1 cm3 was determined as a predictor for pCR, with a sensitivity of 84% and specificity of 47%. In addition, GTV was associated with mrN stage, circumferential resection margin (CRM) status, extramural vascular invasion (EMVI) status, and pretreatment serum CEA level.

Conclusion

Tumor volume and tumor differentiation have significant predictive values in preoperative assessment of pCR among LARC patients. These findings aid clinicians to discriminate those patients who may likely benefit from preoperative regimens and to make optimal treatment plans.

Which tumour factors preclude organ preservation in patients with rectal cancer?

BACKGROUND

cT3cdT4, cN2, mesorectal nodes > 8 mm, clinically positive lateral nodes, extramural vascular invasion (EMVI) and mesorectal fascia threatening (MRF+) have been utilized as exclusion criteria in several studies on the watch-and-wait (w&w) strategy. Here, our aim was to validate these criteria through a post hoc analysis of two pooled prospective studies on w&w following routine radio(chemo)therapy.

METHODS

A review of baseline magnetic resonance imaging was performed in a subgroup of 223 patients treated at a single institution. Of these, 17.9 % started w&w, 12.6 % achieved clinical complete response (cCR) and 9.0 % sustained cCR during median follow-up of 54 months.

RESULTS

The multivariable logistic analysis showed that the proportion of circumferential bowel involvement and EMVI significantly influenced the chance of sustained cCR; odds ratios were 0.063 (95 % confidence interval [CI] 0.008-0.489, p = 0.008), and 0.109 (95 % CI 0.014-0.850, p = 0.034), respectively. Sustained cCR was observed in none of the 57 patients with 90 %-100 % circumferential bowel involvement and in only one of the 89 patients with EMVI. In contrast, cT3cdT4, cN2, mesorectal nodes > 8 mm, clinically positive lateral nodes or MRF+ were not independently associated with sustained cCR. Among the subgroups of patients with these features but without (near-)circular tumour or EMVI+, sustained cCR was observed in 12 %-25 % of patients.

CONCLUSION

Sustained cCR after routine preoperative radio(chemo)therapy is unlikely in patients with (near-)circular tumour or EMVI, whereas patients with cT3cdT4, cN2, mesorectal nodes > 8 mm, clinically positive lateral nodes and MRF+ should not be denied w&w.

The ultimate local failure rate after the watch-and-wait strategy for rectal cancer: a systematic review of literature and meta-analysis

BACKGROUND

We hypothesise that a high rate of tumour regrowth after the watch-and-wait (w&w) strategy may lead, despite salvage surgery, to a significant impairment of ultimate local control compared with immediate surgery.

MATERIALS AND METHODS

To test this hypothesis, we conducted meta-analyses of studies on the w&w strategy (both opportunistic and planned) with an ultimate local failure rate as an endpoint in three patient groups: (1) in all starting radio(chemo)therapy as potential w&w candidates, (2) in a subgroup starting w&w, and (3) in a subgroup with regrowth.

RESULTS

We identified eight studies for evaluation of local failure in group 1 (N = 837) and 36 studies in group 2 (N = 1914) and in group 3 (N = 439). The meta-analysis revealed an ultimate local failure rate of 8.0% (95% CI 4.8%-12.1%) in group 1 and 5.4% (95% CI 3.9%-7.1) in group 2. These rates are similar to those reported in the literature following preoperative chemoradiation and surgery. However, in the most unfavourable group 3 (with regrowth), the rate of ultimate local failure was 24.1% (95% CI 17.9%-30.9%), with the most common causes being patients' refusal of salvage total mesorectal excision (TME) (9.1%), recurrence after salvage TME (7.8%), distant metastases (4.1%), frailty (2.4%), and pelvic tumour unresectability (1.7%).

CONCLUSION

Nearly 25% of patients with regrowth (unfavourable subgroup) experienced ultimate local failure, primarily due to refusing salvage TME. The risk of ultimate local failure in patients initiating radio(chemo)therapy as potential w&w candidates, or in patients starting w&w, appears comparable to that reported after preoperative chemoradiation and surgery. However, this comparison may be biased, because w&w studies included more early tumours compared with surgical studies.

Relationship Between Baseline Rectal Tumor Length and Magnetic Resonance Tumor Regression Grade Response to Chemoradiotherapy: A Subanalysis of the TRIGGER Feasibility Study

BACKGROUND

It is widely believed that small rectal tumors are more likely to have a good response to neoadjuvant treatment, which may influence the selection of patients for a 'watch and wait' strategy.

OBJECTIVE

The aim of this study was to investigate whether there is a relationship between baseline tumor length on magnetic resonance imaging (MRI) and response to chemoradiotherapy.

METHOD

The 96 patients with locally advanced rectal cancer randomised (2:1-intervention:control) in the TRIGGER feasibility study where eligible. Baseline tumor length was defined as the maximal cranio-caudal length on baseline MRI (mm) and was recorded prospectively at study registration. Magnetic resonance tumor regression grade (mrTRG) assessment was performed on the post-chemoradiotherapy (CRT) MRI 4-6 weeks (no later than 10 weeks) post completion of CRT. This was routinely reported for patients in the intervention (mrTRG-directed management) arm and reported for the purposes of this study by the central radiologist in the control arm patients. Those with an mrTRG I/II response were defined as 'good responders' and those with an mrTRG III-V response were defined as 'poor responders'.

RESULTS

Overall, 94 patients had a post-CRT MRI performed and were included. Forty-three (46%) patients had a good response (mrTRG I/II) and 51 (54%) patients had a poor response (mrTRG III/IV). The median tumor length of good responders was 43 mm versus 50 mm (p < 0.001), with considerable overlap in tumor lengths between groups.

CONCLUSION

Baseline tumor length on MRI is not a clinically useful biomarker to predict mrTRG tumor response to CRT and therefore patient suitability for a deferral of surgery trial.

Intentional Watch and Wait or Organ Preservation Surgery Following Neoadjuvant Chemoradiotherapy Plus Consolidation CAPEOX for MRI-defined Low-risk Rectal Cancer: Findings From a Prospective Phase 2 Trial (PKUCH-R01 Trial, NCT02860234)

OBJECTIVE

To assess the efficacy and safety of intentional watch and wait (W&W) and organ preservation surgery following neoadjuvant chemoradiotherapy plus consolidation CAPEOX in magnetic resonance imaging (MRI)-defined low-risk rectal cancer.

BACKGROUND

Clinical T2/early T3 rectal cancers can achieve high yield pathological complete response (ypCR) rates after chemoradiotherapy; thus, an intentional W&W or organ preservation strategy for good clinical responders in these subgroups can be further tested.

METHODS

This prospective, single-arm, phase 2 trial enrolled patients with low-risk MRI prestaged rectal cancers, who concurrently received chemoradiation, followed by four 3-weekly cycles of CAPEOX regimen. Following reassessment, clinical complete response (cCR) or near-cCR patients underwent W&W/organ preservation surgery; the primary endpoint was a 3-year organ preservation rate.

RESULTS

Of the 64 participants, 58 completed treatment, with 6.4% and 33.9% grade 3 to 4 toxicities in the radiotherapy and consolidation CAPEOX phases, respectively, during a median 39.5-month follow-up. Initial cCR, and non-cCR occurred in 33, 13, and 18 patients, respectively. Of the 31 cCR and 7 near-cCR cases managed by W&W, local regrowth occurred in 7; of these, 6 received salvage surgery. The estimated 2-year local regrowth rates were 12.9% [95% confidence interval (CI): 1.1%-24.7%] in cCR and 42.9% (95% CI: 6.2%-79.6%) in near-cCR cases, respectively. Eight patients received local excision, including 2 with regrowth salvage. Lung metastases occurred in 3 patients and multiple metastasis occurred in 1 patient; no local recurrence occurred. The estimated 3-year organ preservation rate was 67.2% (95% CI: 55.6%-78.8%). The estimated 3-year cancer-specific survival, non-regrowth disease-free survival, and stoma-free survival were 96.6% (95% CI: 92.1%-100%), 92.2% (95% CI: 85.5%-98.9%), and 82.7% (95% CI: 73.5%-91.9%), respectively.

CONCLUSIONS

Chemoradiotherapy plus consolidation CAPEOX for MRI-defined low-risk rectal cancer can lead to high rates of organ preservation through intentional W&W or local excision. The oncologic safety of this strategy should be further tested.

Outcomes after the watch-and-wait strategy and local excision treatment for rectal cancer: a meta-analysis

BACKGROUND

The watch-and-wait (W&W) strategy and local excision (LE) have been used in patients with clinical complete response (cCR) for rectal cancer, but the comparative outcomes of the two strategies are controversial. We compared the efficacy of the W&W strategy with LE for rectal cancer patients after neoadjuvant chemoradiotherapy (nCRT) or total neoadjuvant therapy (TNT).

RESEARCH DESIGN AND METHODS

Several domestic and foreign databases were searched for the relevant literature on comparative trials of the W&W strategy and LE surgery for rectal cancer after neoadjuvant therapy with the following outcomes; differences in local recurrence (LR), distant metastasis (DM/DM+LR), 3-year disease-free survival (DFS), 3-year local recurrence-free survival (LRFS) and 3-year overall survival (OS).

RESULTS

Nine articles, were analyzed. Overall, 442 patients were included, with 267 and 175 patients in the W&W and LE groups, respectively. Meta-analysis results showed no significant differences the between W&W and LE groups with respect to LR, DM/DM+LR, 3-year DFS, 3-year LRFS, and 3-year OS. This study has been registered in PROSPERO (registration number: CRD42022331208).

CONCLUSION

The W&W strategy may be preferred for some rectal cancer patients who select LE and reach cCR or near cCR after nCRT or TNT.

Determinants of Pre-Surgical Treatment in Primary Rectal Cancer: A Population-Based Study

When preoperative radiotherapy (RT) is best used in rectal cancer is subject to discussions and guidelines differ. To understand the selection mechanisms, we analysed treatment decisions in all patients diagnosed between 2010-2020 in two Swedish regions (Uppsala with a RT department and Dalarna without). Information on staging and treatment (direct surgery, short-course RT, or combinations of RT/chemotherapy) in the Swedish Colorectal Cancer Registry were used. Staging magnetic resonance imaging (MRI) permitted a division into risk groups, according to national guidelines. Logistic regression explored associations between baseline characteristics and treatment, while Cohen's kappa tested congruence between clinical and pathologic stages. A total of 1150 patients without synchronous metastases were analysed. Patients from Dalarna were older, had less advanced tumours and were pre-treated less often (52% vs. 63%, p < 0.001). All MRI characteristics (T-/N-stage, MRF, EMVI) and tumour levels were important for treatment choice. Age affected if chemotherapy was added. The correlation between clinical and pathological T-stage was fair/moderate and poor for N-stage. The MRI-based risk grouping influenced treatment choice the most. Since the risk grouping was modified to diminish the pre-treated proportion, fewer patients were irradiated with time. MRI staging is far from optimal. A stronger wish to decrease irradiation may explain why fewer patients from Dalarna were irradiated, but inequality in health care cannot be ruled out.

Associations between Response to Commonly Used Neo-Adjuvant Schedules in Rectal Cancer and Routinely Collected Clinical and Imaging Parameters

Complete pathological response (pCR) is achieved in 10−20% of rectal cancers when treated with short-course radiotherapy (scRT) or long-course chemoradiotherapy (CRT) and in 28% with total neoadjuvant therapy (scRT/CRT + CTX). pCR is associated with better outcomes and a “watch-and-wait” strategy (W&W). The aim of this study was to identify baseline clinical or imaging factors predicting pCR. All patients with preoperative treatment and delays to surgery in Uppsala-Dalarna (n = 359) and Stockholm (n = 635) were included. Comparison of pCR versus non-pCR was performed with binary logistic regression models. Receiver operating characteristics (ROC) models for predicting pCR were built using factors with p < 0.10 in multivariate analyses. A pCR was achieved in 12% of the 994 patients (scRT 8% [33/435], CRT 13% [48/358], scRT/CRT + CTX 21% [43/201]). In univariate and multivariate analyses, choice of CRT (OR 2.62; 95%CI 1.34−5.14, scRT reference) or scRT/CRT + CTX (4.70; 2.23−9.93), cT1−2 (3.37; 1.30−8.78; cT4 reference), tumour length ≤ 3.5 cm (2.27; 1.24−4.18), and CEA ≤ 5 µg/L (1.73; 1.04−2.90) demonstrated significant associations with achievement of pCR. Age < 70 years, time from radiotherapy to surgery > 11 weeks, leucocytes ≤ 109/L, and thrombocytes ≤ 4009/L were significant only in univariate analyses. The associations were not fundamentally different between treatments. A model including T-stage, tumour length, CEA, and leucocytes (with scores of 0, 0.5, or 1 for each factor, maximum 4 points) showed an area under the curve (AUC) of 0.66 (95%CI 0.60−0.71) for all patients, and 0.65−0.73 for the three treatments separately. The choice of neoadjuvant treatment in combination with low CEA, short tumour length, low cT-stage, and normal leucocytes provide support in predicting pCR and, thus, could offer guidance for selecting patients for organ preservation.

Active surveillance in long period of total neoadjuvant therapy in rectal cancer: Early prediction of poor regression response

Aim

To analyze locally advanced rectal cancer (LARC) patients and tumor characteristics during the period of total neoadjuvant therapy (TNT) and explore the risk factors that may predict poor tumor regression in response to TNT.

Materials and methods

The data of 120 LARC patients who received TNT from December 2016 and September 2019 in our hospital were retrospectively analyzed. The clinicopathological characteristics of patients with different tumor regression responses were compared. Then we divided patients into two groups according to the carcinoembryonic antigen (CEA) clearance pattern after chemoradiation to explore risk factors that might predict the tumor regression response.

Results

Of 120 LARC patients, 34 (28.3%) exhibited poor regression. Stratified analysis by tumor response showed that patients with poor response to TNT were more likely to obtain elevated CEA during the course of TNT (all P < 0.05). For those with elevated pretreatment CEA, fewer patients with poor response obtained normal CEA after chemoradiation (13.6% vs. 72.7%, P < 0.001). Besides, less patients’ CEA levels in the poor response group decreased by greater than 50% after chemoradiation when compared with that in the good response group (18.2% vs. 60.6%, P = 0.002). Stratified analysis by CEA clearance pattern after chemoradiation showed patients who obtained an elevated pretreatment CEA and decreased by less than 50% after chemoradiation were more likely to have poor response to TNT compared to others (76.2% vs. 18.2%, P < 0.001). Logistic multivariate analysis revealed that cN2 (95% CI 1.553-16.448), larger tumors (95% CI 2.250-21.428) and CEA clearance pattern after chemoradiation (95% CI 1.062-66.992) were independent risk factors for poor tumor regression response.

Conclusion

Approximately one-fourth of LARC patients with TNT achieved a poor regression response. Here, cN2, larger tumor size before treatment and elevated CEA levels were considered predictive features of a poor response. Active surveillance of CEA levels during the TNT course are potentially important, and CEA levels after chemoradiation might have important implications for the tumor response to TNT.

Tumor Volume Predicts for Pathologic Complete Response in Rectal Cancer Patients Treated With Neoadjuvant Chemoradiation

OBJECTIVES

Nonoperative management (NOM) of locally advanced rectal cancer is an emerging approach allowing patients to preserve their anal sphincter. Identifying clinical factors associated with pathologic complete response (pCR) is essential for physicians and patients considering NOM.

MATERIALS AND METHODS

In total, 412 locally advanced rectal cancer patients were included in this retrospective analysis. Tumor volumes were derived from pretreatment MRI. Clinical parameters such as tumor volume, stage, and location were analyzed by univariate and multivariate analysis, against pCR. A receiver operator characteristic curve was generated to identify a tumor volume cut-off with the highest clinically relevant Youden index for predicting pCR.

RESULTS

Seventy-five of 412 patients (18%) achieved pCR. A tumor volume threshold of 37.3 cm 3 was identified as predictive for pCR. On regression analysis, a tumor volume >37.3 cm 3 was associated with a greater than 78% probability of not achieving pCR. On multivariate analysis, a GTV <37.3 cm 3 [odds ratio (OR)=3.7, P <0.0001] was significantly associated with an increased pCR rate, whereas tumor length > 4.85 cm was associated with pCR on univariate (OR=3.03, P <0.01) but not on multivariate analysis (OR=1.45, P =0.261). Other clinical parameters did not impact pCR rates.

CONCLUSIONS

A tumor volume threshold of 37.3 cm 3 was identified as predictive for pCR in locally advanced rectal cancer patients receiving neoadjuvant chemoradiation. Tumors above this volume threshold corresponded to a greater than 78% probability of not achieving pCR. This information will be helpful at diagnosis for clinicians who are considering potential candidates for NOM.

[Complete response after neoadjuvant therapy of rectal cancer: implications for surgery]

For (locally advanced) rectal cancer, a multimodal therapy concept comprising neoadjuvant radiotherapy/chemoradiotherapy, radical surgical resection with partial/complete mesorectal excision and subsequent adjuvant chemotherapy represents the current international standard of care. Further developments in neoadjuvant therapy concepts, such as the principle of total neoadjuvant therapy, lead to an increasing number of patients who show a complete clinical response in restaging after neoadjuvant therapy without clinically detectable residual tumor. In view of the risk associated with radical surgical resection in terms of perioperative morbidity and a potentially non-continence-preserving procedure, the question of the oncological justifiability of an organ-preserving procedure in the case of a complete clinical response under neoadjuvant therapy is increasingly being raised. The therapeutic principle of watch and wait, defined by refraining from immediate radical surgical resection and inclusion in a close-meshed, structured follow-up program, currently appears to be oncologically justifiable based on the current study situation; however, for the initial evaluation of the extent of the clinical response and for the structuring of the close-meshed follow-up program, further optimization and standardization based on broadly designed studies appear necessary in order to be able to provide this concept to a clearly defined patient collective as an oncologically equivalent therapy principle also outside specialized centers.