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

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.

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.

Predicting neoadjuvant chemoradiotherapy response with functional imaging and liquid biomarkers in locally advanced rectal cancer

INTRODUCTION

Non-invasive predictive quantitative biomarkers are required to guide treatment individualization in patients with locally advanced rectal cancer (LARC) in order to maximise therapeutic outcomes and minimise treatment toxicity. Magnetic resonance imaging (MRI), positron emission tomography (PET) and blood biomarkers have the potential to predict chemoradiotherapy (CRT) response in LARC.

AREAS COVERED

This review examines the value of functional imaging (MRI and PET) and liquid biomarkers (circulating tumor cells (CTCs) and circulating tumor nucleic acid (ctNA)) in the prediction of CRT response in LARC. Selected imaging and liquid biomarker studies are presented and the current status of the most promising imaging (apparent diffusion co-efficient (ADC), K^trans, SUV_max, metabolic tumor volume (MTV) and total lesion glycolysis (TLG) and liquid biomarkers (circulating tumor cells (CTCs), circulating tumor nucleic acid (ctNA)) is discussed. The potential applications of imaging and liquid biomarkers for treatment stratification and a pathway to clinical translation are presented.

EXPERT OPINION

Functional imaging and liquid biomarkers provide novel ways of predicting CRT response. The clinical and technical validation of the most promising imaging and liquid biopsy biomarkers in multi-centre studies with harmonised acquisition techniques is required. This will enable clinical trials to investigate treatment escalation or de-escalation pathways in rectal cancer.

Cost analysis of a watch-and-wait approach in patients with a complete clinical response to chemoradiotherapy for rectal cancer

BACKGROUND

There is increasing interest in the watch-and-wait approach for patients with rectal cancer who have had a complete clinical response following neoadjuvant long course chemoradiotherapy. This study is a cost analysis of expenditure on patients in the watch-and-wait program versus patients who underwent standard rectal resection followed by routine surveillance.

METHODS

Data were prospectively collated and retrospectively analysed in all patients who presented with rectal cancer from January 2016 to January 2018 at Sir Charles Gairdner Hospital, Perth, Western Australia. Software developed by the North Metropolitan Health Service was used to capture comprehensive data to calculate the in-hospital expenditure for an individual patient throughout their treatment journey.

RESULTS

For a patient enrolled in the watch-and-wait pathway, the total cost of surveillance over a 5-year period was $45 246. This was compared with the cost of an ultra-low anterior resection/loop ileostomy/closure of loop and routine postoperative surveillance which came to a total of $87 473. While a patient who had an abdominoperineal resection followed by routine 5-year surveillance had an expenditure of $82 290.

CONCLUSION

There is growing evidence that the watch-and-wait strategy is a valid management option. In the cost-conscious environment of the current health care system, the watch-and-wait pathway is a cost-effective and economically advantage treatment.

Value of Primary Rectal Tumor PET/MRI in the Prediction of Synchronic Metastatic Disease

PURPOSE

To analyze the associations between positron emission tomography (PET)/magnetic resonance imaging (MRI) features for primary rectal tumors and metastases.

PROCEDURES

Between November 2016 and April 2018, 101 patients with rectal adenocarcinoma were included in this prospective study (NCT02537340) for whole-body PET/MRI for baseline staging. Two readers analyzed the PET/MRI; they assessed the semiquantitative PET features of the primary tumor and the N- and M-stages. Another reader analyzed the MRI features for locoregional staging. The reference standard for confirming metastatic disease was biopsy or imaging follow-up. Non-parametric tests were used to compare the PET/MRI features of the participants with or without metastatic disease. Binary logistic regression was used to evaluate the associations between the primary tumor PET/MRI features and metastatic disease.

RESULTS

A total of 101 consecutive participants (median age 62 years; range: 33-87 years) were included. Metastases were detected in 35.6% (36 of 101) of the participants. Among the PET/MRI features, higher tumor lesion glycolysis (352.95 vs 242.70; P = .46) and metabolic tumor volume (36.15 vs 26.20; P = .03) were more frequent in patients with than in those without metastases. Additionally, patients with metastases had a higher incidence of PET-positive (64% vs 32%; P = .009) and MRI-positive (56% vs 32%; P = .03) mesorectal lymph nodes, extramural vascular invasion (86% vs 49%; P > .001), and involvement of mesorectal fascia (64% vs 42%; P = .04); there were also differences between the mrT stages of these two groups (P = .008). No differences in the maximum standardized uptake values for the primary tumors in patients with and without metastases were observed (18.9 vs 19.1; P = .56). Multivariable logistic regression showed that extramural vascular invasion on MRI was the only significant predictor (adjusted odds ratio, 3.8 [95% CI: 1.1, 13.9]; P = .001).

CONCLUSION

PET/MRI facilitated the identification of participants with a high risk of metastatic disease, though these findings were based mainly on MRI features.

A Nomogram for Predicting Pathological Complete Response to Neoadjuvant Chemoradiotherapy Using Semiquantitative Parameters Derived From Sequential PET/CT in Locally Advanced Rectal Cancer

We evaluated the predictive value of semiquantitative volumetric parameters derived from sequential PET/CT and developed a nomogram to predict pathological complete response (pCR) in patients with rectal cancer treated by neoadjuvant chemoradiotherapy (nCRT). From April 2008 to December 2013, among the patients who underwent nCRT, those who were taken sequential PET/CT before and after nCRT were included. MRI-based staging and semiquantitative parameters of PET/CT including standardized uptake value (SUV), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were evaluated before and after nCRT. Multivariable analysis was performed to select significant predictors to construct a nomogram. Sensitivity, specificity, accuracy, and area under the receiver operating characteristics curve (AUC) of the model were evaluated to determine its performance. Among 137 eligible patients, 17 (12.4%) had pCR. All post-PET/CT parameters showed significant differences between pCR and non-pCR groups. Patients were randomly assigned to a training group (91 patients) and a validation group (46 patients). In multivariable analysis with the training group, post-CEA, post-MRI T staging, post-SUV_max, and post-MTV were significantly associated with pCR. There was no significant pre-nCRT variable for predicting pCR. Using significant predictors, a nomogram was developed. Sensitivity, specificity, accuracy, and AUC of the nomogram were 0.882, 0.808, 0.848, and 0.884 with the training group and 0.857, 0.781, 0.783, and 0.828 with the validation group, respectively. This model showed the better performance than other predictive models that did not contain PET/CT parameters. A nomogram containing semiquantitative post-PET/CT could effectively select candidates for organ-sparing strategies.

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

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

Value of volumetric and textural analysis in predicting the treatment response in patients with locally advanced rectal cancer

OBJECTIVE

The aim of this study was to assess the value of baseline 18F-FDG PET/CT in predicting the response to neoadjuvant chemo-radiotherapy (NCRT) in patients with locally advanced rectal cancer (LARC) via the volumetric and texture data obtained from 18F-FDG PET/CT images.

METHODS

 In total, 110 patients who had undergone NCRT after initial PET/CT and followed by surgical resection were included in this study. Patients were divided into two groups randomly as a train set (n: 88) and test set (n: 22). Pathological response using three-point tumor regression grade (TRG) and metastatic lymph nodes in PET/CT images were determined. TRG1 were accepted as responders and TRG2-3 as non-responders. Region of interest for the primary tumors was drawn and volumetric features (metabolic tumor volume (MTV) and total lesion glycolysis (TLG)) and texture features were calculated. In train set, the relationship between these features and TRG was investigated with Mann-Whitney U test. Receiver operating curve analysis was performed for features with p < 0.05. Correlation between features were evaluated with Spearman correlation test, features with correlation coefficient < 0.8 were evaluated with the logistic regression analysis for creating a model. The model obtained was tested with a test set that has not been used in modeling before.

RESULTS

 In train set 32 (36.4%) patients were responders. The rate of visually detected metastatic lymph node at baseline PET/CT was higher in non-responders than responders (71.4% and 46.9%, respectively, p = 0.022). There was a statistically significant difference between TLG, MTV, SHAPE_compacity, NGLDMcoarseness, GLRLM_GLNU, GLRLM_RLNU, GLZLM_LZHGE and GLZLM_GLNU between responders and non-responders. MTV and NGLDMcoarseness demonstrated the most significance (p = 0.011). A multivariate logistic regression analysis that included MTV, coarseness, GLZLM_LZHGE and lymph node metastasis was performed. Multivariate analysis demonstrated MTV and lymph node metastasis were the most meaningful parameters. The model's AUC was calculated as 0.714 (p = 0.001,0.606-0.822, 95% CI). In test set, AUC was determined 0.838 (p = 0.008,0.671-1.000, 95% CI) in discriminating non-responders.

CONCLUSIONS

Although there were points where textural features were found to be significant, multivariate analysis revealed no diagnostic superiority over MTV in predicting treatment response. In this study, it was thought higher MTV value and metastatic lymph nodes in PET/CT images could be a predictor of low treatment response in patients with LARC.

Predictive Value of [18F]FDG PET/CT for Lymph Node Metastasis in Rectal Cancer

[¹⁸F]Fluorodeoxyglucose ([¹⁸F]FDG) Positron emission tomography/computed tomography (PET/CT) is commonly used for rectal cancer staging, but improved diagnostic methods for nodal metastases are needed. We aimed to evaluate whether the combination model of the metabolic tumor volume of primary tumor (T_MTV) and maximum standardized uptake value of lymph node (N_SUVmax) on pretreatment [¹⁸F]FDG PET/CT could improve nodal metastases prediction in rectal cancer. We enrolled a total of 166 rectal cancer patients who underwent pretreatment [¹⁸F]FDG PET/CT and surgical resection without neoadjuvant treatment between January 2009 and August 2016. Visual and semiquantitative PET/CT parameters were obtained. Associations between clinicopathological, PET/CT-derived variables and nodal metastases were evaluated by logistic regression analysis. Nodal metastases were confirmed histologically in 68 of the 166 patients (41%). Uni- and multivariate analyses demonstrated T_MTV and N_SUVmax were independent predictive factors for nodal metastases. The c-statistics of the combination model was 0.806 (Standard Error, 0.034; 95% Confidence Interval, 0.737-0.863), which showed significant improvement compared to T_MTV (0.698, P = 0.0002) or N_SUVmax (0.720, P = 0.0008) alone. T_MTV and N_SUVmax are independently correlated with nodal metastases. Furthermore, the combination model showed improved performance for risk prediction; thus, [¹⁸F]FDG PET/CT might have a role in rectal cancer staging and treatment planning.

Does baseline [18F] FDG-PET/CT correlate with tumor staging, response after neoadjuvant chemoradiotherapy, and prognosis in patients with rectal cancer?

BACKGROUND

[18F] fluorodeoxyglucose positron emission tomography/computed tomography ([18F] FDG-PET/CT) may be used for tumor staging and prognosis in several tumors but its role in rectal cancer is still debated. The aim of the present study was to assess the correlation of baseline [18F] FDG-PET parameters with tumor staging, tumor response (tumor regression grade (TRG)), and outcome in a series of patients affected by locally advanced rectal cancer (LARC) treated with neoadjuvant chemoradiotherapy (CRT).

METHODS

One hundred patients treated with neoadjuvant CRT and radical surgery were enrolled in the present study. Maximum standardized uptake value (SUVmax), SUVmean, metabolic tumor volume (MTV), and total lesion glycolysis (TLG) at the baseline [18F] FDG-PET were calculated. These PET parameters were correlated with tumor staging, histopathological data (TRG1 vs. TRG2-5 and TRG1-2 vs. TRG3-5), disease-free survival, and overall survival.

RESULTS

SUVmax and SUVmean of primary tumor were statistically associated with T4-stage. SUVmax, SUVmean, and TLG did not result statistically associated with TRG (TRG1 or TRG1-2). MTV resulted statistically associated with TRG1-2 group (OR 2.9; 95% CI 1.2-7.1). Finally, no PET parameter was significantly associated with disease-free or overall survival.

CONCLUSION

Our results showed that baseline [18F] FDG-PET parameters correlated with tumor staging, and only MTV correlated with TRG 1-2. PET parameters failed to predict disease-free and overall survival after treatment completion. The results leave open to further studies the issue of identifying patients suitable for conservative approaches.

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.

'Watch and wait' in rectal cancer: summary of the current evidence

BACKGROUND

The management of rectal cancer has evolved considerably over the last few decades with increasing use of neoadjuvant chemoradiotherapy (nCRT). Complete clinical response (cCR) and even complete pathological response (pCR) have been noted in a proportion of patients who had surgery after nCRT. This raises the concern that we may have been 'over-treating' some of these patients and lead to an increasing interest in 'watch and wait' (W&W) approach for patients who had cCR to avoid the morbidity associated with rectal surgery.

METHODS

A review of the literature in English pertaining to rectal cancer in the context of W&W, organ preservation and active surveillance.

RESULTS

Evidence available to support W&W approach comes from non-randomised controlled trials (RCTs) with no current consensus on patients' selection criteria, lack of viable predictors of both cCR and pCR and lack of universal definitions of cCR and pCR. Also, there is no agreed protocol for disease surveillance.

CONCLUSION

Even though there has been increasing reports on the outcomes of W&W in rectal cancer, the current evidence cannot support its routine use in clinical practice. This approach should be used in clinical trials settings or after thorough counselling with the patient on the outcomes of various treatment options.

Long-term outcomes of clinical complete responders after neoadjuvant treatment for rectal cancer in the International Watch & Wait Database (IWWD): an international multicentre registry study

BACKGROUND

The strategy of watch and wait (W&W) in patients with rectal cancer who achieve a complete clinical response (cCR) after neoadjuvant therapy is new and offers an opportunity for patients to avoid major resection surgery. However, evidence is based on small-to-moderate sized series from specialist centres. The International Watch & Wait Database (IWWD) aims to describe the outcome of the W&W strategy in a large-scale registry of pooled individual patient data. We report the results of a descriptive analysis after inclusion of more than 1000 patients in the registry.

METHODS

Participating centres entered data in the registry through an online, highly secured, and encrypted research data server. Data included baseline characteristics, neoadjuvant therapy, imaging protocols, incidence of local regrowth and distant metastasis, and survival status. All patients with rectal cancer in whom the standard of care (total mesorectal excision surgery) was omitted after neoadjuvant therapy were eligible to be included in the IWWD. For the present analysis, we only selected patients with no signs of residual tumour at reassessment (a cCR). We analysed the proportion of patients with local regrowth, proportion of patients with distant metastases, 5-year overall survival, and 5-year disease-specific survival.

FINDINGS

Between April 14, 2015, and June 30, 2017, we identified 1009 patients who received neoadjuvant treatment and were managed by W&W in the database from 47 participating institutes (15 countries). We included 880 (87%) patients with a cCR. Median follow-up time was 3·3 years (95% CI 3·1-3·6). The 2-year cumulative incidence of local regrowth was 25·2% (95% CI 22·2-28·5%), 88% of all local regrowth was diagnosed in the first 2 years, and 97% of local regrowth was located in the bowel wall. Distant metastasis were diagnosed in 71 (8%) of 880 patients. 5-year overall survival was 85% (95% CI 80·9-87·7%), and 5-year disease-specific survival was 94% (91-96%).

INTERPRETATION

This dataset has the largest series of patients with rectal cancer treated with a W&W approach, consisting of approximately 50% data from previous cohort series and 50% unpublished data. Local regrowth occurs mostly in the first 2 years and in the bowel wall, emphasising the importance of endoscopic surveillance to ensure the option of deferred curative surgery. Local unsalvageable disease after W&W was rare.

FUNDING

European Registration of Cancer Care financed by European Society of Surgical Oncology, Champalimaud Foundation Lisbon, Bas Mulder Award granted by the Alpe d'Huzes Foundation and Dutch Cancer Society, and European Research Council Advanced Grant.

Putting down the scalpel in rectal cancer management - a historical perspective

The surgical management of rectal cancer has evolved from a disease without any possibility of cure in the early 1700s where surgical management consisted of the palliative drainage of disease related abscesses to the present day where surgical cure is not only possible but also possible with sphincter or even organ preservation. Prof Habr-Gama's lecture describes the evolution of the surgical management of rectal cancer and the current focus on organ preservation.

Value of FDG-PET/CT Volumetry After Chemoradiotherapy in Rectal Cancer

BACKGROUND

Neoadjuvant chemoradiotherapy followed by an optimal surgery is the standard treatment for patients with locally advanced rectal cancer. FDG-PET/CT is commonly used as the modality for assessing the effect of chemoradiotherapy.

OBJECTIVE

The purpose of this study was to investigate whether PET/CT-based volumetry could contribute to the prediction of pathological complete response or prognosis after neoadjuvant chemoradiotherapy.

DESIGN

This was a retrospective cohort study.

SETTINGS

This study was conducted at a single research center.

PATIENTS

Ninety-one consecutive patients with locally advanced rectal cancer were enrolled between January 2005 and December 2015.

INTERVENTION

Patients underwent PET/CT before and after neoadjuvant chemoradiotherapy.

MAIN OUTCOME MEASURES

Maximum standardized uptake value and total lesion glycolysis on PET/CT before and after neoadjuvant chemoradiotherapy were calculated using isocontour methods. Correlations between these variables and clinicopathological factors and prognosis were assessed.

RESULTS

PET/CT-associated variables before chemoradiotherapy were not correlated with either clinicopathological factors or prognosis. Maximum standardized uptake value was associated with pathological complete response, but total lesion glycolysis was not. Maximum standardized uptake value correlated with ypT, whereas total lesion glycolysis correlated with both ypT and ypN. High total lesion glycolysis was associated with a considerably poorer prognosis; the 5-year recurrence rate was 65% and the 5-year mortality rate 42%, whereas in lesions with low total lesion glycolysis, these were 6% and 2%. On multivariate analysis, high total lesion glycolysis was an independent risk factor for recurrence (HR = 4.718; p = 0.04).

LIMITATIONS

The gain in fluoro-2-deoxy-D-glucose uptake may differ between scanners, thus the general applicability of this threshold should be validated.

CONCLUSIONS

In patients with locally advanced rectal cancer, high total lesion glycolysis after neoadjuvant chemoradiotherapy is strongly associated with a worse prognosis. Total lesion glycolysis after chemoradiotherapy may be a promising preoperative predictor of recurrence and death. See Video Abstract at http://links.lww.com/DCR/A464.

Junior E, Machado AM, Mamede M. Individualized threshold for tumor segmentation in 18F-FDG PET/CT imaging: The key for response evaluation of neoadjuvant chemoradiation therapy in patients with rectal cancer?

Summary Introduction: The standard treatment for locally advanced rectal cancer (RC) consists of neoadjuvant chemoradiation followed by radical surgery. Regardless the extensive use of SUVmax in 18F-FDG PET tumor uptake as representation of tumor glycolytic consumption, there is a trend to apply metabolic volume instead. Thus, the aim of the present study was to evaluate a noninvasive method for tumor segmentation using the 18F-FDG PET imaging in order to predict response to neoadjuvant chemoradiation therapy in patients with rectal cancer. Method: The sample consisted of stage II and III rectal cancer patients undergoing 18F-FDG PET/CT examination before and eight weeks after neoadjuvant therapy. An individualized tumor segmentation methodology was applied to generate tumor volumes (SUV2SD) and compare with standard SUVmax and fixed threshold (SUV40%, SUV50% and SUV60%) pre- and post-therapy. Therapeutic response was assessed in the resected specimens using Dworak's protocol recommendations. Several variables were generated and compared with the histopathological results. Results: Seventeen (17) patients were included and analyzed. Significant differences were observed between responders (Dworak 3 and 4) and non-responders for SUVmax-2 (p<0.01), SUV2SD-2 (p<0.05), SUV40%-2 (p<0.05), SUV50%-2 (p<0.05) and SUV60%-2 (p<0.05). ROC analyses showed significant areas under the curve (p<0.01) for the proposed methodology with sensitivity and specificity varying from 60% to 83% and 73% to 82%, respectively. Conclusion: The present study confirmed the predictive power of the variables using a noninvasive individualized methodology for tumor segmentation based on 18F-FDG PET/CT imaging for response evaluation in patients with rectal cancer after neoadjuvant chemoradiation therapy.

Management of the Complete Clinical Response

Organ preservation is considered in the management of selected patients with rectal cancer. Complete clinical response observed after neoadjuvant chemoradiation for rectal cancer is one of these cases. Patients who present complete clinical response are candidates to the watch-and-wait approach, when radical surgery is not immediately performed and is offered only to patients in the event of a local relapse. These patients are included in a strict follow-up, and up of 70% of them will never be operated during the follow-up. This strategy is associated with similar oncological outcomes as patients operated on, and the advantage of avoiding the morbidity associated to the radical operation. In this article we will discuss in detail the best candidates for this approach, the protocol itself, and the long-term outcomes.

FDG PET/CT radiomics for predicting the outcome of locally advanced rectal cancer

PURPOSE

The aim of this study was to investigate the prognostic value of baseline ¹⁸F-FDG PET/CT textural analysis in locally-advanced rectal cancer (LARC).

METHODS

Eighty-six patients with LARC underwent ¹⁸F-FDG PET/CT before treatment. Maximum and mean standard uptake values (SUVmax and SUVmean), metabolic tumoral volume (MTV), total lesion glycolysis (TLG), histogram-intensity features, as well as 11 local and regional textural features, were evaluated. The relationships of clinical, pathological and PET-derived metabolic parameters with disease-specific survival (DSS), disease-free survival (DFS) and overall survival (OS) were assessed by Cox regression analysis. Logistic regression was used to predict the pathological response by the Dworak tumor regression grade (TRG) in the 66 patients treated with neoadjuvant chemoradiotherapy (nCRT).

RESULTS

The median follow-up of patients was 41 months. Seventeen patients (19.7%) had recurrent disease and 18 (20.9 %) died, either due to cancer progression (n = 10) or from another cause while in complete remission (n = 8). DSS was 95% at 1 year, 93% at 2 years and 87% at 4 years. Weight loss, surgery and the texture parameter coarseness were significantly associated with DSS in multivariate analyses. DFS was 94 % at 1 year, 86 % at 2 years and 79 % at 4 years. From a multivariate standpoint, tumoral differentiation and the texture parameters homogeneity and coarseness were significantly associated with DFS. OS was 93% at 1 year, 87% at 2 years and 79% after 4 years. cT, surgery, SUVmean, dissimilarity and contrast from the neighborhood intensity-difference matrix (contrast_NGTDM) were significantly and independently associated with OS. Finally, RAS-mutational status (KRAS and NRAS mutations) and TLG were significant predictors of pathological response to nCRT (TRG 3-4).

CONCLUSION

Textural analysis of baseline ¹⁸F-FDG PET/CT provides strong independent predictors of survival in patients with LARC, with better predictive power than intensity- and volume-based parameters. The utility of such features, especially coarseness, should be confirmed by larger clinical studies before considering their potential integration into decisional algorithms aimed at personalized medicine.

New Strategies in Rectal Cancer

In recent years, our understanding of rectal cancer has improved, including how locally advanced disease responds to chemotherapy and radiation. This has led to new innovations and advances in the treatment of rectal cancer, which includes organ-preserving strategies for responsive disease, and minimally invasive approaces for the performance of total mesorectal excision/protectomyh for persistently advanced disease. This article discusses new strategies for rectal cancer therapy, including Watch and Wait, local excision, minimally invasive proctectomy, and transanal total mesorectal excision particularly in the setting of preoperative multimodality treatment.