Evaluation of lateral pelvic nodes in patients with advanced rectal cancer. AJR Am J Roentgenol. 2014;202:1245-1255. [PMID: 24848821 DOI: 10.2214/ajr.13.11228]

A combined diagnostic model including middle rectal artery visualization for predicting lateral lymph node metastasis in rectal cancer

Purpose

This study attempted to establish a combined diagnostic model encompassing visualization of the middle rectal artery (MRA) and other imaging features to improve the diagnostic efficiency of lateral lymph node (LLN) metastasis, which is crucial for clinical decision-making in rectal cancer.

Method

One hundred eleven patients receiving bilateral or unilateral lymph node dissection were enrolled, and 140 cases of LLN status on a certain unilateral pelvic sidewall were selected. Enhanced computed tomography (CT) was used to determine whether MRA was visible. Multivariable regression was used to establish a diagnostic model combining MRA visualization with other imaging features to predict LLN metastasis. Receiver operating characteristic (ROC) curve and area under the ROC curve (AUC) were used to test the diagnostic efficacy for LLN metastasis. Ten-fold cross-validation was completed to internally validate the diagnostic model.

Results

Of the 140 LLNs harvested from 111 patients, 76 were positive and 64 were negative for metastases, respectively. The diagnostic model combining the MRA visualization and lymph node short diameter showed a greater efficiency than a single scale (AUC = 0.945, 95% confidence interval = 0.893-0.976, P < 0.001). The mean cross-validated AUC was 0.869 (95% confidence interval = 0.835-0.903).

Conclusion

Our results establish a combined diagnostic model with the help of MRA visualization to yield a high diagnostic efficiency of LLN metastasis in rectal cancer.

Opportunities and challenges of indocyanine green in gastrointestinal cancers for intraoperative and nano-medicine application

The morbidity and mortality of gastrointestinal tumours remain high worldwide. Surgical resection is currently the most critical radical therapeutic schedule, while postoperative complications and sentinel lymph node (SLN) identification are closely related to the outcome. Indocyanine green (ICG)-mediated fluorescence imaging is increasingly being used in gastrointestinal surgery. It has been embraced by various surgical disciplines as a potential method to improve lymph node detection and enhance surgical field visualization. ICG can passively concentrate in SLN because of enhanced permeation and retention effects. After excitation by near-infrared light devices, SLN can display higher intensity fluorescence, helping visualization for better lymph node dissection. In addition, visual assessment of intestinal blood flow through ICG may reduce the incidence of anastomotic leakage. Although it has good clinical application, ICG-imaging still faces some problems, such as a higher false-negative rate, poorly targeted biodistribution, and lower fluorescence contrast, due to the lack of active tumour targeting. Thus, different ICG-coupled nanoparticles with inherent characteristics or functional modification-enhanced SLN identification features for gastrointestinal cancers bring benefit through active tumour targeting, superior tumour-background ratio, and high resolution. Nano-ICG combined with potential substances, including enhanced imaging contrast and/or combination therapy (chemotherapy, targeted therapy, immunotherapy, etc.), have been packaged and accumulated in the tumour area through active targeting for multimodal imaging and treatment. In this review, we outline the intraoperative application and possible future nanodirections of ICG in gastrointestinal cancer. The prospects and challenges of nano-ICG diagnostic and therapeutic methods in clinical applications are also discussed.

Graphical Abstract

Post-hoc analysis of clinicopathological factors affecting lateral lymph node metastasis based on STELLAR study for rectal cancer

PURPOSE

In post-hoc analyses of phaseIII randomized controlled study(STELLAR), to analyzethe prognostic impact oflateral pelvic lymph node (LPLN)metastasis in locally advanced rectal cancer (LARC).

METHODS

LPLN metastasis was defined as a short diameter > 7 mm on magnetic resonance imaging (MRI).The studyincluded 591 patients with LARC.All patients received neoadjuvant (chemo)radiotherapy combined withradical resection.

RESULTS

Among 591 patients, 99 (16.8 %) were diagnosed with LPLN metastasis, mostly with unilateral metastasis (79.8 %), with internal iliac lymph node metastasis being more common (81.8 %).Significant differences were found among with and without LPLN metastasis in rectal segmentation (P=0.001),N disease (P<0.001), mesenteric LN metastasis or not (P=0.030). The median follow-up timewas 34.0 months, three-year disease-free survival (DFS),overall survival (OS), andmetastasis-free survival (MFS)were significantly lower in LPLN metastaticgroup than those in LPLN non-metastaticgroup (51.4 % vs. 68.2 %, P<0.001; 71.8 % vs. 84.2 %, P=0.006; 60.8 % vs. 80.1 %,P<0.001), respectively; while there were no significant differences in locoregional recurrence(11.4 % vs. 8.5 %, P=0.564). Multivariate analysis found that LPLN metastasis was an independent prognostic factor affecting DFS (P=0.005), OS (P=0.036),MFS (P=0.001).No significantly survival benefit was observed for the short-term radiotherapy based total neoadjuvant therapy compared to long-term concurrent chemoradiotherapy.

CONCLUSIONS

LPLN metastasis observed byMRI should be considered in LARC patients, especially in populations with lowrectal cancer, N2 disease, and mesenteric LN metastasis. LPLN metastasis diagnosed by MRI is a significant and independent risk factor and is associated with worse DFS, OS, MFS.

Role of Lateral Pelvic Node Dissection in Rectal Cancer Surgery

The role of lateral pelvic lymph node dissection in the treatment of patients with locally advanced rectal cancer is a matter of controversy. Surgical practices in Korea and Japan have accepted this approach and are widely utilized; however, it is not routinely incorporated in the practice of countries in the Western hemisphere. This review will examine the role of lateral pelvic lymph node dissection.

The influence of neoadjuvant chemoradiotherapy combined with lateral lymph nodes dissection or not on the local recurrence of low to intermediate-stage II/III rectal cancer

BACKGROUND

Currently, the treatment options for stage II/III rectal cancer with preoperative lateral lymph nodes (LLN) enlargement are highly controversial between East and West, and the indications for diagnosing suspiciously positive enlarged LLN are inconsistent both nationally and internationally. Oriental scholars (especially Japanese) consider the LLN as a regional disease, they consider that prophylactic lateral lymph nodes dissection (LLND), regardless of whether the LLN is enlarged or not, is considered necessary if the tumor is found beneath the peritoneal reflex and invades the muscle layer. Western scholars regard LLN as distant metastases, recommending neoadjuvant chemoradiotherapy (nCRT) in conjunction with total rectal mesenteric resection (TME). In recent years, it has been found that neither of the two standard treatment regimens, East and West, significantly improved local control of tumors in patients with LLN enlargement. In contrast, nCRT combined with LLND significantly lowers the local recurrence (LR) rate. It has also been suggested that combination therapy regimens do not improve patient prognosis but increase treatment-related complications. Therefore, the suitable therapeutic option for rectal cancer with an enlarged LLN needs to be further explored.

AIM

Exploring appropriate treatment options for low to intermediate-stage II/III rectal cancer with LLN enlargement, as well as risk variables that may affect the LR in these patients with LLN enlarged.

METHODS AND PATIENTS

In this research, we retrospectively analyzed 110 patients with locally advanced mid-low (low boundary of tumor is no more than 10 cm from the anus) rectal cancer who were treated at Harbin Medical University Cancer Hospital arranged from 2017.1 to 2020.6. These patients had received nCRT and TME, and their initial rectal nuclear magnetic resonance imaging (MRI) revealed an enlarged LLN (short axis of LLN, SA ≥ 5 mm). Of these, 40 patients underwent LLND, thus, 110 patients were grouped into two groups: nCRT+TME (LLND-, n = 70) and nCRT+TME + LLND (LLND+, n = 40), and their 3 years prognoses were compared.

RESULTS

After a median follow-up of 49.0 months, the 3-year LR rate of the LLND- group was notably greater than the LLND+ group (22.8% vs. 7.5%, p = 0.04). However, there was no noteworthy difference in the 3-year progression-free survival (PFS, 70.5% vs. 77.5%, p > 0.05) rate or distant metastasis (DM) rate (20.0% vs. 17.5%, p > 0.05). Additionally, the LLND+ group experienced significantly more postoperative complications than the LLND- group (15.0% vs. 4.2%, p = 0.05). Subgroups analysis for the LLND- group revealed that patients with LLN short axis regression (ΔSA) > 35.9% after nCRT had significantly lower 3-year LR rate than patients with ΔSA ≤ 35.9% (9.1% vs. 35.1%, p = 0.01). Patients in the LLND- group with ΔSA > 35.9%, however, had comparable 3-year LR rate and DM rates to those in the LLND+ group.

CONCLUSION

LLN is an independent indicator for prognosis among people with low to intermediate-stage II/III malignant rectal tumors. Patients with poor SA regression (ΔSA ≤ 35.9%) after nCRT have a greater risk of positive LLN and a more substantial LR, and nCRT combined with LLND reduced the LR rate significantly, but considerably prolonged operative time, surgical bleeding, and postoperative complications. Patients with better SA regression (ΔSA > 35.9%), however, have a lower possibility of LR and might not need LLN clearance, in these cases, nCRT+TME is advised.

Can patients with good tumor regression grading after neoadjuvant chemoradiotherapy be exempted from lateral lymph node dissection?

OBJECTIVE

To investigate whether lateral lymph node (LLN) dissection (LLND) can be exempted in patients with good tumor regression grading (TRG) after neoadjuvant chemoradiotherapy (nCRT)?

METHODS

A retrospective study was conducted on consecutive patients with advanced rectal cancer who underwent nCRT and total mesorectal resection plus selective LLND at our institution. The primary outcomes are the relationship between LLN metastasis (LLNM) and magnetic resonance imaging TRG (mrTRG) and the relationship between LLNM and pathological TRG (pTRG).

RESULTS

A total of 91 patients were included, of which 24 patients (26.4%) had LLNM, 67 patients (73.6%) had no LLNM. There were significant differences of the maximum short-axis of LLN before and after nCRT, short-axis reduction rate of the LLN with maximum short-axis, length diameter reduction rate of primary tumor, mrTRG, and pTRG between the two groups. Multivariate logistic regression showed that mrTRG (P = 0.026) and pTRG (P = 0.013) were independent predictors for LLNM. The combination used by mrTRG and the maximum short-axis of LLNs ≥ 8 mm before nCRT and the maximum short-axis of LLN ≥ 5 mm after nCRT achieved specificity of 0.970, positive predictive value (PPV) of 0.867, and negative predictive value (NPV) of 0.855. The same combination used by pTRG achieved the specificity of 0.970, PPV of 0.857 and NPV of 0.844.

CONCLUSION

The suspected positive LLNs tend to be sterilized by nCRT in patients who have a very good response to nCRT. It is rational to avoid LLND in patients whose primary tumor and LLNs both show good response to nCRT.

T1 rectal mucinous adenocarcinoma with bilateral enlarged lateral lymph nodes and unilateral metastasis: A case report

BACKGROUND

There are a few cases of lateral lymph node (LLN) metastasis (LLNM) of T1 rectal cancer. Moreover, LLNM is easily missed, especially in patients with early-stage rectal cancer. To our knowledge, the possibility of bilateral LLNM before surgery has not been reported in previous studies.

CASE SUMMARY

A 36-year-old woman underwent endoscopic submucosal dissection at a local hospital owing to a clinical diagnosis of a rectal polyp. The pathology report showed a diagnosis of T1 rectal mucinous adenocarcinoma. She was considered to have bilateral LLNM after the examination at our hospital. Laparoscopic total mesorectal excision plus bilateral LLN dissection was performed and the pathological outcomes indicated unilateral LLNM. The patient received long-course adjuvant chemoradiotherapy with no recurrence or metastasis observed during the 1-year follow-up period.

CONCLUSION

T1 rectal cancer could lead to LLNM and possibly, bilateral LLNM. Therefore, adequate clinical evaluation is essential for these patients.

MRI for Rectal Cancer: Staging, mrCRM, EMVI, Lymph Node Staging and Post-Treatment Response

Rectal cancer is a relatively common malignancy in the United States. Magnetic resonance imaging (MRI) of rectal cancer has evolved tremendously in recent years, and has become a key component of baseline staging and treatment planning. In addition to assessing the primary tumor and locoregional lymph nodes, rectal MRI can be used to help with risk stratification by identifying high-risk features such as extramural vascular invasion and can assess treatment response for patients receiving neoadjuvant therapy. As the practice of rectal MRI continues to expand further into academic centers and private practices, standard MRI protocols, and reporting are critical. In addition, it is imperative that the radiologists reading these cases work closely with surgeons, medical oncologists, radiation oncologists, and pathologists to ensure we are providing the best possible care to patients. This review aims to provide a broad overview of the role of MRI for rectal cancer.

From "East vs West" towards international multidisciplinary collaboration: An appraisal of lateral lymph nodes in rectal cancer

Western and Eastern practices have traditionally differed in their approach to treating lateral lymph nodes in rectal cancer. While Western clinicians have primarily favored neoadjuvant (chemo)radiotherapy to sterilize lateral compartments, Eastern physicians have often opted for the surgical removed of lymphatic tissue with a lateral lymph node dissection without neoadjuvant treatment. The literature suggests similar oncological outcomes for these two separate techniques, while tangible differences exist. The combination of these paradigms may be beneficial in reducing overall morbidity while sustaining low recurrence rates. This article considers traditional Eastern and Western perspectives, discusses nodal features important for predicting malignancy and attempts to stimulate international, multidisciplinary consensus and collaboration.

Long-Term Results of a Prospective Phase 2 Study on Volume De-Escalation in Neoadjuvant Chemoradiotherapy of Rectal Cancer

PURPOSE

In the current study, we evaluated whether neoadjuvant chemoradiotherapy with reduced treatment volumes due to the exclusion of elective pelvic nodal irradiation is a feasible strategy for selected patients with locally advanced rectal cancer.

METHODS AND MATERIALS

Patients with T2 low-lying/T3, N0-N1 rectal lesions without evidence of disease in the lateral lymph nodes were prospectively recruited. All patients underwent pretreatment testing, including computed tomography imaging of the chest, abdomen, and pelvis with intravenous contrast, pelvic magnetic resonance imaging with intravenous contrast, and 18-fluorodeoxyglucose positron emission/computed tomography. The clinical target volume included the primary tumor and the mesorectum with vascular supply containing the perirectal and presacral nodes, with the upper border at the S2/S3 interspace. The total radiation dose was 50.4 Gy, and fluoropyrimidine-based chemotherapy was associated concomitantly. The primary endpoint of the study was the reduction of gastrointestinal (GI) toxicity, and the secondary endpoints were pathologic complete response, local control, overall survival, and disease-free survival.

RESULTS

Fifty-two patients (30 men, 22 women) with a median age of 67 years (range, 45-85 years) were enrolled in the study. Acute grade 3 GI toxicity was 7.6%, and there were no cases of grade 4 toxicity. Three patients (5.7%) developed a local recurrence. No relapse occurred in the lateral lymph nodes. The local control rate at 5 years was 96.1%. With a median follow-up time of 72.9 months (range, 2.5-127.6 months), the 3- and 5-year overall survival rates were 89.4% and 87%, respectively. The 3- and 5-year disease-free survival rates were 82.4% and 82.4%, respectively.

CONCLUSIONS

De-escalation of radiation therapy target volume reduces GI side effects without compromising efficacy in patients with rectal cancer. These results cannot be clearly extended to high-risk disease and need further evaluation in future randomized trials.

Lateral lymph node dissection reduces local recurrence of locally advanced lower rectal cancer in the absence of preoperative neoadjuvant chemoradiotherapy: a systematic review and meta-analysis

Background

The impact of lateral lymph node dissection (LLND) in locally advanced lower rectal cancer remains controversial. This study is to compare total mesorectal excision (TME) with or without LLND in lower rectal cancer cases of stage II/III.

Methods

The electronic databases were systematically searched that compared TME with or without LLND among patients with lower rectal cancer in clinical stage II/III. Subgroup analysis was performed considering neoadjuvant chemoradiotherapy (nCRT). The hazard ratios (HR), relative risk (RR), and weighted mean difference (WMD) were pooled.

Results

Twelve studies of 4458 patients of this meta-analysis demonstrate, LLND alone significantly reduced the local recurrence rate of patients who did not receive nCRT (RR 0.71, P = 0.004), while the difference was not significant when combined with nCRT (RR 0.70, P = 0.36). The analysis shows TME with LLND was associated with significantly longer operation time (WMD 90.73 min, P < 0.001), more intraoperative blood loss (WMD 303.20 mL, P < 0.001), and postoperative complications (RR = 1.35, P =0.02). Whereas urinary dysfunction (RR 1.44, P = 0.38), sexual dysfunction (RR 1.41, P = 0.17), and postoperative mortality (RR = 1.52, P = 0.70), were similar between these two groups. Statistically, no significant differences were observed in OS (HR 0.93, P = 0.62), DFS (HR 0.99, P = 0.96), total recurrence (RR 0.98, P = 0.83), lateral recurrence (RR 0.49, P = 0.14), or distal recurrence (RR 0.95, P = 0.78) between these two groups regardless of whether nCRT was performed or not.

Conclusions

The study shows LLND alone decreases the local recurrence without using nCRT irrespective of the survival advantage in locally advanced lower rectal cancer. The benefit of controlling local recurrence by LLND alone makes us reconsider the usage of nCRT with LLND.

Trial registration

The protocol for this meta-analysis was registered prospectively with PROSPERO (CRD42020135575) on 16 May 2019.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12957-020-02078-1.

Lateral pelvic lymph node dissection in the management of locally advanced low rectal cancer: Summary of the current evidence

Lateral pelvic lymph nodes (LPLN) are a major site for local recurrence following curative resection for low locally advanced rectal cancer. Ongoing advances in imaging techniques have improved predicting LPLN metastasis (LPLNM) during pre-operative staging. However, there is ongoing debate on optimal management of this subgroup of patients with variation between guidance of different societies. In Japan, LPLNM is considered as local disease and addressed by lateral pelvic node dissection (LPLND) in addition to total mesorectal excision (TME). However, in the west, LPLNM is considered as metastatic disease and those patients are offered neoadjuvant chemoradiotherapy (nCRT) followed by TME surgery. The potential surgical risks and morbidity associated with LPLND as well as the uncertainty of the oncological outcome have raised the concern that patients with locally advanced low rectal cancer with LPLNM could be over or under-treated. A comprehensive review of literature was performed, summarizing the current evidence on available modalities for predicting LPLNM, the role of LPLND in the management of advanced low rectal cancer and the available surgical approaches with their impact on surgical and oncological outcomes. LPLND is associated with increased operative time, blood loss and post-operative morbidity. The potential benefits for local disease control and survival still awaits high quality studies. There has been increasing number of reports of the use minimally invasive approaches in LPLND in an attempt to reduce post-operative complications. There is need for high quality evidence to define the role of LPLND in management of patients with advanced low rectal cancer.

Selective lateral lymph node dissection after neoadjuvant chemoradiotherapy in rectal cancer

BACKGROUND

Lateral lymph node metastasis is one of the leading causes of local recurrence in patients with advanced mid or low rectal cancer. Neoadjuvant chemoradiotherapy (NCRT) can effectively reduce the postoperative recurrence rate; thus, NCRT with total mesorectal excision (TME) is the most widely accepted standard of care for rectal cancer. The addition of lateral lymph node dissection (LLND) after NCRT remains a controversial topic.

AIM

To investigate the surgical outcomes of TME plus LLND, and the possible risk factors for lateral lymph node metastasis after NCRT.

METHODS

This retrospective study reviewed 89 consecutive patients with clinical stage II-III mid or low rectal cancer who underwent TME and LLND from June 2016 to October 2018. In the NCRT group, TME plus LLND was performed in patients with short axis (SA) of the lateral lymph node greater than 5 mm. In the non-NCRT group, TME plus LLND was performed in patients with SA of the lateral lymph node greater than 10 mm. Data regarding patient demographics, clinical workup, surgical procedure, complications, and outcomes were collected. Multivariate logistic regression analysis was performed to evaluate the possible risk factors for lateral lymph node metastasis in NCRT patients.

RESULTS

LLN metastasis was pathologically confirmed in 35 patients (39.3%): 26 (41.3%) in the NCRT group and 9 (34.6%) in the non-NCRT group. The most common site of metastasis was around the obturator nerve (21/35) followed by the internal iliac artery region (12/35). In the NCRT patients, 46% of patients with SA of LLN greater than 7 mm were positive. The postoperative 30-d mortality rate was 0%. Two (2.2%) patients suffered from lateral local recurrence in the 2-year follow up. Multivariate analysis showed that cT4 stage (odds ratio [OR] = 5.124, 95% confidence interval [CI]: 1.419-18.508; P = 0.013), poor differentiation type (OR = 4.014, 95%CI: 1.038-15.520; P = 0.044), and SA ≥ 7 mm (OR = 7.539, 95%CI: 1.487-38.214; P = 0.015) were statistically significant risk factors associated with LLN metastasis.

CONCLUSION

NCRT is not sufficient as a stand-alone therapy to eradicate LLN metastasis in lower rectal cancer patients and surgeons should consider performing selective LLND in patients with greater LLN SA diameter, poorer histological differentiation, or advanced T stage. Selective LLND for NCRT patients can have a favorable oncological outcome.

Oncological Outcomes of Patients with Locally Advanced Rectal Cancer and Lateral Pelvic Lymph Node Involvement

INTRODUCTION

The optimal management of patients with radiologically positive lateral pelvic lymph nodes in locally advanced rectal cancer remains unclear. We compared local recurrence rates and oncological outcomes of patients with locally advanced cancer with and without lateral pelvic lymph nodes.

METHODS

Patients who underwent curative surgery for stage III rectal adenocarcinoma between 2009 and 2014 and had a preoperative MRI at our institution as well as preoperative neoadjuvant treatment were included. Patients with positive lateral pelvic lymph nodes (iliac or obturator nodes) on preoperative MRI (LPND +) were compared to patients with no lateral pelvic nodal disease (LPND -). Data were collected from a prospectively maintained institutional database. Differences between the groups were compared in univariate analysis. Log-rank test was used to evaluate overall and disease-free survival between the groups.

RESULTS

A total of 125 patients met inclusion criteria with a mean age of 56.3 ± 12.2 and 75% were male. Median follow-up was 44 months (IQR 32, 106). Positive LPND was present on preoperative MRI in 43/125 (34.4%) patients who were in the LPND (+) group. Seventeen out of 43 patients had a post-neoadjuvant treatment MRI and 15 patients had a decrease in size of nodes or disappearance of LPND. On univariate analysis, LPND (+) and LPND (-) groups were comparable. Local recurrence rates were higher in the LPND (+) group, although this was not statistically significant (16.3% vs. 6%, p = 0.06). Overall and disease-free survival rates were comparable between the LPND (+) and LPND (-) groups (p = 0.97, p = 0.51).

CONCLUSIONS

Management of patients with advanced rectal cancer and radiologically positive lateral pelvic lymph nodes is challenging due to high local recurrence rates. Further studies are needed to develop care pathways for the optimal treatment processes.

Predictive factors of pathological lateral pelvic lymph node metastasis in patients without clinical lateral pelvic lymph node metastasis (clinical stage II/III): The analysis of data from the clinical trial (JCOG0212)

BACKGROUND

Mesorectal excision (ME) is the standard surgical procedure for lower rectal cancer. However, in Japan, total or tumor-specific ME with lateral pelvic lymph node dissection (LLND) is the standard surgical procedure for patients with clinical stages II or III lower rectal cancer, because lateral pelvic lymph node metastasis occasionally occurs in these patients. The aim of study was to elucidate the predictive factors of pathological lateral pelvic lymph node metastasis in patients without clinical lateral pelvic lymph node metastasis.

METHODS

Data form the clinical trial (JCOG0212) was analyzed. The JCOG0212 was a randomized controlled trial to confirm the non-inferiority of mesorectal excision alone to mesorectal excision with lateral lymph node dissection for clinical stage II/III patients who don't have clinical lateral pelvic lymph node metastasis in terms of relapse free survival. This study was conducted at a multitude of institution33 major hospitals in Japan. Among the 351 patients who underwent lateral lymph node dissection in the JCOG0212 study, 328 patients were included in this study. Associations between pathological lateral pelvic lymph node metastasis and preoperative and postoperative factors were investigated. The preoperative factors were age, sex, clinical stage, tumor location, distance from anal verge, tumor size, and short-axis diameter of lateral pelvic lymph node on computed tomography and the postoperative factors were pathological T, pathological N, and histological grade.

RESULTS

Among the 328 patients, 24 (7.3%) had pathological lateral pelvic lymph node metastasis. In multivariable analysis of the preoperative factors, patient age (p = 0.067), tumor location (p = 0.025), and short-axis diameter of lateral pelvic lymph node (p = 0.002) were significantly associated with pathological lateral pelvic lymph node metastasis.

CONCLUSIONS

Patient age, tumor location, and short-axis diameter of lateral pelvic lymph node were predictive factors of pathological lateral pelvic lymph node metastasis.

Accuracy of F-18 FDG PET/CT with optimal cut-offs of maximum standardized uptake value according to size for diagnosis of regional lymph node metastasis in patients with rectal cancer

BACKGROUND

The low sensitivity of F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) for the evaluation of metastatic lymph nodes (LNs) is mainly due to the partial volume effect in patients with rectal cancer. This retrospective study evaluated the diagnostic accuracy of F-18 FDG PET/CT with optimal cut-off values of the maximum standardized uptake value (SUV_max), according to LN size, for the evaluation of regional LN in rectal cancer patients.

METHODS

This study included 176 patients with rectal cancer who underwent F-18 FDG PET/CT for initial staging. Patients were classified based on the long-axis diameter of the regional LN on CT images as small (≤ 7 mm; n = 118) and large (> 7 mm; n = 58) LN groups. The optimal cut-off value of SUV_max was determined for each group, using receiver operating characteristic curve analysis. Areas under the curve (AUC) were compared by C-statistics using two methods: the cut-off value of SUV_max optimized according to LN size, and a fixed SUV_max cut-off value of 2.5.

RESULTS

The optimal cut-off values of SUV_max for the small and large LN groups were 1.1, and 2.1, respectively. The sensitivity, specificity, and accuracy of F-18 FDG PET/CT using the optimal cut-off values were 90.6, 70.9, and 76.3% in the small LN group, and 68.6, 78.3, and 72.4% in the large LN group. The sensitivity, specificity, and accuracy of F-18 FDG PET/CT using the fixed cut-off value were 18.8, 100, and 78.0% in the small LN group, and 51.4, 87.0, and 65.5% in the large LN group. The AUC was significantly higher using the optimal cut-off values than the fixed cut-off value (0.808 vs. 0.594, p = 0.005) in the small LN group, but not in the large LN group (0.734 vs. 0.692, p = 0.429).

CONCLUSIONS

Application of the lower cut-off value of SUV_max improves the diagnostic performance of F-18 FDG PET/CT for the evaluation of small regional LNs in patients with rectal cancer.

Preferential use of imaging modalities in staging newly diagnosed rectal cancer: a survey of US radiation oncologists

Background

Accurate staging is crucial for management of patients with newly diagnosed rectal cancer. Endorectal ultrasound (EUS) has been the standard modality in the United States for decades, with magnetic resonance imaging (MRI) now preferred by national guidelines. Positron emission tomography (PET), conversely, is not recommended. The current utilization of imaging modalities by American radiation oncologists in staging newly diagnosed rectal cancer is unknown.

Methods

American radiation oncologists completed an anonymous institutional review board-approved online survey probing their imaging preferences for initial staging of rectal cancer patients.

Results

We received 220 responses from American radiation oncologists, with 39% in academic centers and with 45% seeing more than 10 rectal cancer patients per year. Most respondents utilize all three imaging modalities for rectal cancer staging-EUS, MRI and positron emission tomography/computed tomography (PET/CT). Fifty-two percent and 38% of respondents are high utilizers of EUS and MRI, respectively, defined as ordering these tests at least 75% of the time. Forty seven percent were high PET utilizers. The latter was associated with practice in a private setting (P=0.015) and being within 10 years from residency training completion (P<0.01).

Conclusions

Our analysis reveals a dramatic discordance among national guidelines and the practice patterns among American radiation oncologists. More rely on PET for initial staging of rectal cancer patients than on pelvic MRI. Further research needs to determine the most effective imaging work-up of patients with an initial diagnosis of rectal cancer.

Diagnostic performance of 18F-FDG PET/CT using point spread function reconstruction on initial staging of rectal cancer: a comparison study with conventional PET/CT and pelvic MRI

Background

Accurate staging is crucial for treatment selection and prognosis prediction in patients with rectal cancer. Point spread function (PSF) reconstruction can improve spatial resolution and signal-to-noise ratio of PET imaging. The aim of this study was to evaluate the effectiveness of ¹⁸F-FDG PET/CT with PSF reconstruction for initial staging in rectal cancer compared with conventional PET/CT and pelvic MRI.

Methods

A total of 59 patients with rectal cancer underwent preoperative ¹⁸F-FDG PET/CT and pelvic MRI. The maximum standardized uptake value (SUVmax) and lesion to background (L/B) ratio of possible metastatic lymph nodes, and metabolic tumor volumes (MTVs) of primary tumors were calculated. For N and T (T1-2 vs T3-4) staging, sensitivities, specificities, positive predictive values, negative predictive values, and accuracies were compared between conventional PET/CT [reconstructed with ordered subset expectation maximization (OSEM)], PSF-PET/CT (reconstructed with OSEM+PSF), and pelvic MRI. Histopathologic analysis was the reference standard.

Results

For N staging, PSF-PET/CT provided higher sensitivity (78.6%) than conventional PET/CT (64.3%), and pelvic MRI (57.1%), and all techniques showed high specificity (PSF-PET: 95.4%, conventional PET: 96.7%, pelvic MRI: 93.5%). SUVmax and L/B ratio were significantly higher in PSF-PET/CT than conventional-PET/CT (p < 0.001). The accuracy for T staging in PSF-PET/CT (69.4%) was not significantly different to conventional PET/CT (73.5%) and pelvic MRI (73.5%). MTVs of PSF and conventional PET showed a significant difference among T stages (p < 0.001), with higher values in advanced stages. In M staging, both PSF and conventional PET/CT diagnosed all distant metastases correctly.

Conclusions

PSF-PET/CT produced images with higher lesion-to-background contrast than conventional PET/CT, which allowed improved detection of lymph node metastasis without compromising specificity, and showed comparable diagnostic value to MRI in local staging. PSF-PET/CT is likely to have a great value for initial staging in rectal cancer.

How Should Imaging Direct/Orient Management of Rectal Cancer?

Modern rectal cancer management is dependent on preoperative staging, and radiological assessment is a crucial part of this process. Imaging must provide sufficient information to guide preoperative decision-making that is reliable and reproducible. Different methods have been used for local staging; however, magnetic resonance imaging (MRI) has shown to be the most reliable tool for this purpose. MRI offers prognostic information about the patients and guides the decision between neoadjuvant treatment and total mesorectal excision alone. Also, not only the initial staging but also restaging by MRI can provide significant information regarding tumor response that is essential when considering alternative approaches.

Magnetic resonance imaging of rectal cancer: staging and restaging evaluation

Magnetic resonance imaging is used to non-invasively stage and restage rectal adenocarcinomas. Accurate staging is important as the depth of tumor extension and the presence or absence of lymph node metastases determines if an individual will undergo preoperative neoadjuvant chemoradiation. Accurate description of tumor location is important for presurgical planning. The relationship of the tumor to the anal sphincter in addition to the depth of local invasion determines the surgical approach used for resection. High-resolution T2-weighted imaging is the primary sequence used for initial staging. The addition of diffusion-weighted imaging improves accuracy in the assessment of treatment response on restaging scans. Approximately 10%-30% of individuals will experience a complete pathologic response following chemoradiation with no residual viable tumor found in the resected specimen at histopathologic assessment. In some centers, individuals with no residual tumor visible on restaging MR who are thought to be at high operative risk are monitored with serial imaging and a "watch and wait" approach in lieu of resection. Normal rectal anatomy, MR technique utilized for staging and restaging scans, and TMN staging are reviewed. An overview of surgical techniques used for resection including newer, minimally invasive endoluminal techniques is included.