Observation of "complete clinical response" in rectal cancer after neoadjuvant chemoradiation: The Flinders experience

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.

Curative therapy for rectal cancer

Introduction: A comprehensive trimodality approach has become the standard of care for patients with locally advanced rectal cancer. However, the sequencing and duration of chemotherapy and chemoradiotherapy around surgery varies between clinical studies and geographical regions. Growing evidence is also mounting for strategies such as total neoadjuvant therapy and non-operative management for carefully selected patients.Areas covered: We provide a perspective review of the current evidence and controversies in the treatment of locally advanced rectal cancer including the recent updates from the 2020 ASCO annual conference.Expert opinion: With ongoing advances in the management of locally advanced rectal cancer, a multidisciplinary team approach is necessary as treatments could involve multiple approaches. Chemoradiotherapy whether short or long course followed by at least 3 months of systemic chemotherapy may be the preferred option to balance local and distant disease control. Albeit the choice of doublet or triplet chemotherapy is still controversial. As total neoadjuvant treatment becomes part of the standard of care in rectal cancer, modification of the surveillance schedule is needed to detect early recurrences which may be limited by resources and availability of services.

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

Objective

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

Materials and Methods

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

Results

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

Conclusion

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

Management of early-stage gastro-esophageal cancers: expert perspectives from the Australasian Gastrointestinal Trials Group (AGITG) with invited international faculty

Introduction: A multimodal approach in operable early-stage oesophago-gastric (OG) cancer has evolved in the last decade, leading to improvement in overall outcomes.Areas covered: A review of the published literature and conference abstracts was undertaken on the topic of optimal adjunctive chemotherapy or chemoradiotherapy in early-stage OG cancers. This review article focuses on the current evidence pertaining to neoadjuvant and perioperative strategies in curable OG cancers including the evolving landscape of immunotherapy and targeted drugs in this setting.Expert commentary: Adjunctive therapies in the form of preoperative chemo-radiotherapy (CRT) or chemotherapy and perioperative chemotherapy over surgery alone improve outcomes in patients with operable OG cancer. Although there are variations in practice around the world, a multi-disciplinary approach to patient care is of paramount importance. Immunotherapy and on treatment functional imaging are two examples of emerging strategies to improve the outcome for early-stage patients. A better understanding of the molecular biology of this disease may help overcome the problem of tumor heterogeneity and enable more rationally designed and targeted therapeutic interventions in the future.

Circulating epigenetic biomarkers for detection of recurrent colorectal cancer

Background

The sensitive detection of recurrent colorectal cancer (CRC) by the measurement of circulating tumor DNA (ctDNA) might improve the chance of a cure. This study compared a quantitative methylated ctDNA test with carcinoembryonic antigen (CEA) in the setting of surveillance for recurrence.

Methods

Blood samples collected either during surveillance or within 12 months of the confirmation of recurrence were assayed for ctDNA (methylated branched‐chain amino acid transaminase 1 [BCAT1]/Ikaros family zinc‐finger 1 protein [IKZF1]) and CEA. The optimal ctDNA threshold was determined by receiver operating characteristic analysis, and the test performance for the detection of recurrence was compared with CEA (5 ng/mL threshold).

Results

The study cohort comprised 144 eligible patients and included 50 recurrence events. The sensitivity of the methylated ctDNA test for recurrence was 66.0% (95% confidence interval [CI], 57.1%‐69.3%), which was significantly higher than the sensitivity of CEA (31.9%; 95% CI, 22.8%‐36.6%; P < .001). The sensitivity for resectable recurrence (n = 20) was also higher (ctDNA, 60.0%; CEA, 20.0%; P = .01). The specificity did not differ between the tests (ctDNA, 97.9%; 95% CI, 93.2%‐99.6%; CEA, 96.4%; 95% CI, 91.4%‐99.0%). When adjustments were made for other predictors of the presence of recurrence, a positive ctDNA test was an independent predictor (odds ratio, 155.7; 95% CI, 17.9‐1360.6; P < .001), whereas CEA was not (odds ratio, 2.5; 95% CI, 0.3‐20.6; P = .407).

Conclusions

The quantitative ctDNA test showed superior sensitivity in comparison with CEA without a difference in the specificity for detecting recurrent CRC. Longitudinal studies are warranted to further assess the utility (specifically the survival benefit) of methylated BCAT1/IKZF1 ctDNA in the surveillance of patients with CRC.

An optimal positivity threshold has been determined for an epigenetic circulating tumor DNA panel of biomarkers (methylated BCAT1 and IKZF1), and it has been applied to investigating the panel's utility in the detection of colorectal cancer recurrence. The sensitivity of the circulating tumor DNA test is superior to that of the clinically used carcinoembryonic antigen test for all recurrences (66% vs 32%) and those considered curable (60% vs 20%), with both tests having a very high specificity (98% vs 96%).

The Use of Circulating Tumor DNA to Monitor and Predict Response to Treatment in Colorectal Cancer

Background: Colorectal cancer is one of the most common cancers worldwide and has a high mortality rate following disease recurrence. Treatment efficacy is maximized by providing tailored cancer treatment, ideally involving surgical resection and personalized neoadjuvant and adjuvant therapies, including chemotherapy, radiotherapy and increasingly, targeted therapy. Early detection of recurrence or disease progression results in more treatable disease and is essential to improving survival outcomes. Recent advances in the understanding of tumor genetics have resulted in the discovery of circulating tumor DNA (ctDNA). A growing body of evidence supports the use of these sensitive biomarkers in detecting residual disease and diagnosing recurrence as well as enabling targeted and tumor-specific adjuvant therapies. Methods: A literature search in Pubmed was performed to identify all original articles preceding April 2019 that utilize ctDNA for the purpose of monitoring response to colorectal cancer treatment. Results: Ninety-two clinical studies were included. These studies demonstrate that ctDNA is a reliable measure of tumor burden. Studies show the utility of ctDNA in assessing the adequacy of surgical tumor clearance and changes in ctDNA levels reflect response to systemic treatments. ctDNA can be used in the selection of targeted treatments. The reappearance or increase in ctDNA, as well as the emergence of new mutations, correlates with disease recurrence, progression, and resistance to therapy, with ctDNA measurement allowing more sensitive monitoring than currently used clinical tools. Conclusions: ctDNA shows enormous promise as a sensitive biomarker for monitoring response to many treatment modalities and for targeting therapy. Thus, it is emerging as a new way for guiding treatment decisions-initiating, altering, and ceasing treatments, or prompting investigation into the potential for residual disease. However, many potentially useful ctDNA markers are available and more work is needed to determine which are best suited for specific purposes and for improving specific outcomes.

A systematic review and meta-analysis of pT2 rectal cancer spread and recurrence pattern: Implications for target design in radiation therapy for organ preservation

BACKGROUND

There are no guidelines on clinical target volume (CTV) delineation for cT2 rectal cancer treated with organ preservation.

MATERIALS AND METHODS

A systematic review and meta-analysis were performed to determine the extent of distal mesorectal (DMS) and distal intramural spread (DIS), the risk of lateral lymph node (LLN) metastases in pT2 tumours, and regional recurrence pattern after organ preservation.

RESULTS

The rate of DMS > 1 cm was 1.9% (95% CI: 0.4-5.4%), maximum extent: 1.3 cm. The rate of DIS > 0.5 cm was 4.7% (95% CI: 1.3-11.5%), maximum extent: 0.8 cm. The rate of LLN metastases was 8.2% (95% CI: 6.7-9.9%) for tumours below or at peritoneal reflexion and 0% for higher tumours. Regional nodal recurrences alone were recorded in 1.0% (95% CI: 0.5-1.7%) of patients after watch-and-wait and in 2.1% (95% CI: 1.2-3.4%) after preoperative radiotherapy and local excision. Thus, the following rules for CTV delineation are proposed: caudal border 1.5 cm from the tumour to account for DMS or 1 cm to account for DIS, whichever is more caudal; cranial border at S2/S3 interspace; inclusion of LLN for tumours at or below peritoneal reflexion. A planning study was performed in eight patients to compare dose-volume parameters obtained using these rules to that obtained using current guidelines for advanced cancers. The proposed rules led to a mean 18% relative reduction of planning target volume, which resulted in better sparing of organs-at-risk.

CONCLUSION

This meta-analysis suggests a smaller CTV for cT2 tumours than the current guidelines designed for advanced cancers.