MRI assessment and outcomes in patients receiving neoadjuvant chemotherapy only for primary rectal cancer: long-term results from the GEMCAD 0801 trial

Clinical significance of the EMD/mesorectum ratio of T3 mid-low rectal cancer: A retrospective observational study

Previous studies suggested that the extramural distance (EMD) should be considered in therapeutic decision-making of rectal cancer because it can be used as an indicator of the T3 subclassification; however, reports of impact of EMD/mesorectum ratio on prognosis are rare.The objectives of this study were to evaluate the feasibility of the extramural distance EMD/mesorectum ratio as a maker of the T3 subclassification for T3 mid-low rectal cancer and find the potential radiological marker on MRI for neoadjuvant chemoradiotherapy (nCRT).From December 2012 to December 2016, 287 consecutive patients with MRI-staged T3 mid-low rectal cancer were enrolled. The EMD was defined as the distance from the outer edge of the muscularis propria to the outer edge of tumor, and the mesorectum was measured as the distance from outer edge of muscularis propria to mesorectal fascia (MRF) in the same layer. The association of the EMD/mesorectum ratio and other MRI or clinicopathological factors with survival was analyzed. The independent prognostic factors were estimated by Cox regression analysis.The mean EMD/mesorectum ratio was 0.43. Based on ROC analysis, we chose a EMD/mesorectum ratio of 0.3 for further analyses. Of 287 patients, 163 (56.8%) had a EMD/mesorectum ratio ≥ 0.3. Patients with an EMD/mesorectum ratio ≥ 0.3 had a decreased recurrence free survival (RFS) and overall survival (OS) (P < .001; P = .034, respectively). Of the 163 patients, patients with nCRT had a higher RFS than patients without nCRT (P = .001). Multivariate analysis showed that the EMD/mesorectum ratio was the only independent prognostic factors for RFS.Our study provided evidence that the EMD/mesorectum ratio could be used for T3 subclassification, the optimal cut-off value of EMD/mesorectum ratio was 0.3 when the ratio was applied to classify T3 mid-low rectal cancer patients, and nCRT should be performed for these patients when the EMD/mesorectum ratio is ≥ 0.3.

Pelvic MRI after induction chemotherapy and before long-course chemoradiation therapy for rectal cancer: What are the imaging findings?

OBJECTIVES

To determine the appearance of rectal cancer on MRI after oxaliplatin-based chemotherapy (ICT) and make a preliminary assessment of MRI's value in predicting response to total neoadjuvant treatment (TNT).

METHODS

In this IRB-approved, HIPAA-compliant, retrospective study between 1 January 2010-20 October 2014, pre- and post-ICT tumour T2 volume, relative T2 signal intensity (rT2SI), node size, signal intensity and border characteristics were assessed in 63 patients (65 tumours) by three readers. The strength of association between the reference standard of histopathological percent tumour response and tumour volume change, rT2SI and lymph node characteristics was assessed with Spearman's correlation coefficient and Wilcoxon's rank sum test. Cox regression was used to assess association between DFS and radiological measures.

RESULTS

Change in T2 volume was not associated with TNT response. Change in rT2SI showed correlation with TNT response for one reader only using selective regions of interest (ROIs) and borderline correlation with response using total volume ROI. There was a significant negative correlation between baseline and post-ICT node size and TNT response (r = -0.25, p = 0.05; r = -0.35, p = 0.005, readers 1 and 2, respectively). Both baseline and post-induction median node sizes were significantly smaller in complete responders (p = 0.03, 0.001; readers 1 and 2, respectively). Change in largest baseline node size and decrease in post-ICT node signal heterogeneity were associated with 100% tumour response (p = 0.04). Nodal sizes at baseline and post-ICT MRI correlated with DFS.

CONCLUSION

In patients undergoing post-ICT MRI, tumour volume did not correlate with TNT response, but decreased lymph node sizes were significantly associated with complete response to TNT as well as DFS. Relative T2SI showed borderline correlation with TNT response.

KEY POINTS

• MRI-based tumour volume after induction chemotherapy and before chemoradiotherapy did not correlate with overall tumour response at the end of all treatment. • Lymph node size after induction chemotherapy and before chemoradiotherapy was strongly associated with complete pathological response after all treatment. • Lymph node sizes at baseline and post-induction chemotherapy MRI correlated with disease-free survival.

Magnetic resonance tumour regression grade and pathological correlates in patients with rectal cancer

BACKGROUND

Evidence to support the specific use of magnetic resonance tumour regression grade (mrTRG) is inadequate. The aim of this study was to investigate the pathological characteristics of mrTRG after chemoradiotherapy (CRT) for rectal cancer and the implications for surgery.

METHODS

Patients undergoing long-course CRT (45-50 Gy plus a booster dose of 4-6 Gy) for mid or low rectal cancer (cT3-4 or cN+ without metastasis) between 2011 and 2015 who had post-CRT rectal MRI before surgery were included retrospectively. Three board-certified experienced radiologists assessed mrTRG. mrTRG was correlated with pathological tumour regression grade (pTRG), ypT and ypN. In a subgroup of patients with mrTRG1-2 and no tumour spread (such as nodal metastasis) on MRI, the projected rate of completion total mesorectal excision (TME) if they underwent transanal excision (TAE) and had a ypT status of ypT2 or higher was estimated, and recurrence-free survival was calculated according to the operation (TME or TAE) that patients had actually received.

RESULTS

Some 439 patients (290 men and 149 women of mean(s.d.) age 62·2(11·4) years) were analysed. The accuracy of mrTRG1 for predicting pTRG1 was 61 per cent (40 of 66), and that for ypT1 or less was 74 per cent (49 of 66). For mrTRG2, these values were 22·3 per cent (25 of 112) and 36·6 per cent (41 of 112) respectively. Patients with mrTRG1 and mrTRG2 without tumour spread were ypN+ in 3 per cent (1 of 29) and 16 per cent (8 of 50) respectively. Assuming mrTRG1 or mrTRG1-2 with no tumour spread on post-CRT MRI as the criteria for TAE, the projected completion TME rate was 26 per cent (11 of 43) and 41·0 per cent (41 of 100) respectively. For the 100 patients with mrTRG1-2 and no tumour spread, recurrence-free survival did not differ significantly between TME (79 patients) and TAE (21) (adjusted hazard ratio 1·86, 95 per cent c.i. 0·42 to 8·18).

CONCLUSION

Patients with mrTRG1 without tumour spread may be suitable for TAE.

MRI-based EMVI positivity predicts systemic recurrence in rectal cancer patients with a good tumor response to chemoradiotherapy followed by surgery

BACKGROUND

This study aimed to determine the prognostic value of baseline magnetic resonance imaging-based extramural vascular invasion status (EMVI) among rectal cancer patients with a good tumor response to standard chemoradiotherapy followed by surgery.

METHODS

A total of 359 patients with ypT0-2/N0 disease from The Yonsei Multicenter Colorectal Cancer Electronic Database were retrospectively included between January 2000 and December 2014. Magnetic resonance images and medical records were reviewed to investigate risk factors for tumor recurrence.

RESULTS

When we compared patients without and with EMVI, significant differences were observed in the 5-year disease-free survival rate (DFS) (80.8% vs 57.8%, P = 0.005) and in the 5-year systemic recurrence-free survival rate (SRFS) (86.9% vs 64.3%, P = 0.007). In the multivariate analysis, both mrEMVI and APR independently predicted overall DFS (APR; HR 2.088, 95% CI: 1.082-4.031, P = 0.028, mrEMVI; HR: 2.729, 95% CI: 1.230-6.058, P = 0.014). mrEMVI was only independent prognostic factor for systemic recurrence with statistical significance (HR: 3.321, 95% CI: 1.185-9.309, P = 0.022).

CONCLUSION

Even in rectal cancer patients with a good response to chemoradiotherapy followed by curative surgery, extramural vascular invasion and APR may predict poor disease-free survival outcomes. Intensified treatment strategy should be considered.

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

Purpose of Review

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

Recent Findings

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

Summary

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

PARP inhibitors in platinum-sensitive high-grade serous ovarian cancer

Purpose

Poly(ADP-ribose) polymerase inhibitors (PARPi) have changed the management of high-grade serous ovarian cancer (HGSOC). The rationale for the development of PARPi was based on the concept of synthetic lethality, in which a cell can survive a deficiency of one gene/gene product, but may die if there is a deficiency in a combination of genes/gene products. In women with BRCA1/2 deficiency within their ovarian cancer tissue, inhibition of PARP imposes an intolerable burden of DNA damage repair deficiency and may induce cell death.

Methods

Clinical trials have evaluated PARPi as single-agent therapeutics and as maintenance treatment following platinum-based chemotherapy for HGSOC. Clinical data suggest the most impressive anti-tumour activity occurs in women with platinum-sensitive ovarian cancer and germline or somatic BRCA1/2 mutations (g/sBRCAmt).

Results

In the maintenance setting, randomised trials have shown that PARPi compared to placebo reduce the hazard ratio for the development of progressive disease to 0.2–0.27 for patients with a g/sBRCAmt; to 0.34–0.38 for patients with putative evidence of DNA damage repair deficiency; and to 0.35–0.45 in an unselected population with HGSOC. Furthermore, phase 1/2 trials have reported single-agent anti-tumour response rates in gBRCAmt of approximately 50% in platinum-sensitive and 25% in platinum-resistant disease.

Conclusion

Here, we discuss the evidence for the use of PARPi as single-agent therapeutics and maintenance treatment in HGSOC and evaluate the genetic assays used in clinical trials so far. We discuss the emerging role of platinum sensitivity as a broad eligibility criteria for the use of PARPi.

Novel radiomic signature as a prognostic biomarker for locally advanced rectal cancer

BACKGROUND

Locally advanced rectal cancer (LARC) patient stratification by clinicoradiologic factors may yield variable results. Therefore, more efficient prognostic biomarkers are needed for improved risk stratification of LARC patients, personalized treatment, and prognostication.

PURPOSE/HYPOTHESIS

To compare the ability of a radiomic signature to predict disease-free survival (DFS) with that of a clinicoradiologic risk model in individual patients with LARC.

STUDY TYPE

Retrospective study.

POPULATION

In all, 108 consecutive patients (allocated to a training and validation set with a 1:1 ratio) with LARC treated with neoadjuvant chemoradiotherapy (nCRT) followed by total mesorectal excision (TME).

FIELD STRENGTH/SEQUENCE

Axial 3D LAVA multienhanced MR sequence at 3T.

ASSESSMENT

ITK-SNAP software was used for manual segmentation of 3D pre-nCRT MR images. All manual tumor segmentations were performed by a gastrointestinal tract radiologist, and validated by a senior radiologist. The clinicoradiologic risk factors with potential prognostic outcomes were identified in univariate analysis based on the Cox regression model for the whole set. The results showed that ypT, ypN, EMVI, and MRF were potential clinicoradiologic risk factors. Interestingly, only ypN and MRF were identified as independent predictors in multivariate analysis based on the Cox regression model.

STATISTICAL TESTS

A radiomic signature based on 485 3D features was generated using the least absolute shrinkage and selection operator (LASSO) Cox regression model. The association of the radiomic signature with DFS was investigated by Kaplan-Meier survival curves. Survival curves were compared by the log-rank test. Three models were built and assessed for their predictive values, using the Harrell concordance index and integrated time-dependent area under the curve.

RESULTS

The novel radiomic signature stratified patients into low- and high-risk groups for DFS in the training set (hazard ratio [HR] = 6.83; P < 0.001), and was successfully validated in the validation set (HR = 2.92; P < 0.001). The model combining the radiomic signature and clinicoradiologic findings had the best performance (C index = 0.788, 95% confidence interval [CI] 0.72-0.86; integrated time-dependent area under the curve of 0.837 at 3 years).

DATA CONCLUSION

The novel radiomic signature could be used to predict DFS in patients with LARC. Furthermore, combining this radiomic signature with clinicoradiologic features significantly improved the ability to estimate DFS (P = 0.001, 0.005 in training set and in validation set, respectively), and may help guide individualized treatment in such patients.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2018.

DNA hypermethylation as a predictor of extramural vascular invasion (EMVI) in rectal cancer

PURPOSE

DNA hypermethylation in gene promoter regions (CpG islands) is emerging as an important pathway in colorectal cancer tumourigenesis. Whilst genetic mutations have been associated with extramural vascular invasion (EMVI) in rectal cancer, no such association has yet been made with epigenetic factors.

METHODS

100 consecutive neoadjuvant-naïve patients undergoing curative surgery for rectal were classified according to the presence or absence of EMVI on histopathological examination. DNA was extracted from tumours and subjected to bisulfite conversion and methylation-specific PCR to determine CIMP status (high, intermediate, or low; according to a validated panel of 8 genes). CIMP status was correlated with EMVI status, histopathological, clinical, and demographic variables, in addition to overall (OS) and disease free (DFS) survival.

RESULTS

51 patients were characterised as CIMP-low, 48 CIMP-intermediate, and one patient CIMP-high. EMVI-positivity was associated with CIMP-intermediate epigenotype (p < 0.001). Patients with EMVI-positive tumours were found to have significantly more advanced disease by pT, pN, and pAJCC categorisation (p = 0.002, p < 0.001, and = p < 0.001, respectively). EMVI-positivity was significantly associated with the requirement for adjuvant chemotherapy (p < 0.001), and worse DFS but not OS (p = 0.012 and p = 0.052).

CONCLUSIONS

Given the association between CIMP-intermediate epigenotype and EMVI-positivity, and the subsequent disadvantage in pathological stage, requirement for adjuvant therapy and worse survival, tumour epigenotyping could potentially play an important role in personalising patients' cancer care. Further work is required to understand the mechanisms that underlie the observed effect, with the hope that they may provide novel opportunities for intervention and inform treatment decisions in rectal cancer.