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

The Additional Role of F18-FDG PET/CT in Characterizing MRI-Diagnosed Tumor Deposits in Locally Advanced Rectal Cancer

Rationale: F18-FDG PET/CT may be helpful in baseline staging of patients with high-risk LARC presenting with vascular tumor deposits (TDs), in addition to standard pelvic MRI and CT staging. Methods: All patients with locally advanced rectal cancer that had TDs on their baseline MRI of the pelvis and had a baseline F18-FDG PET/CT between May 2016 and December 2020 were included in this retrospective study. TDs as well as lymph nodes identified on pelvic MRI were correlated to the corresponding nodular structures on a standard F18-FDG PET/CT, including measurements of nodular SUVmax and SUVmean. In addition, the effects of partial volume and spill-in on SUV measurements were studied. Results: A total number of 62 patients were included, in which 198 TDs were identified as well as 106 lymph nodes (both normal and metastatic). After ruling out partial volume effects and spill-in, 23 nodular structures remained that allowed for reliable measurement of SUVmax: 19 TDs and 4 LNs. The median SUVmax between TDs and LNs was not significantly different (p = 0.096): 4.6 (range 0.8 to 11.3) versus 2.8 (range 1.9 to 3.9). For the median SUVmean, there was a trend towards a significant difference (p = 0.08): 3.9 (range 0.7 to 7.8) versus 2.3 (range 1.5 to 3.4). Most nodular structures showing either an SUVmax or SUVmean ≥ 4 were characterized as TDs on MRI, while only two were characterized as LNs. Conclusions: SUV measurements may help in separating TDs from lymph node metastases or normal lymph nodes in patients with high-risk LARC.

Diagnostic value of a radiomics model based on CT and MRI for prediction of lateral lymph node metastasis of rectal cancer

This study aimed to develop a radiomics model for predicting lateral lymph node (LLN) metastasis in rectal cancer patients using MR-T2WI and CT images, and assess its clinical value. This prospective study included rectal cancer patients with complete MR-T2WI and portal enhanced CT images who underwent LLN dissection at Tianjin Union Medical Center between June 2017 and November 2022. Primary lesions and LLN were segmented using 3D slicer. Radiomics features were extracted from the region of interest using pyradiomics in Python. Least absolute shrinkage and selection operator algorithm and backward stepwise regression were employed for feature selection. Three LLN metastasis radiomics prediction models were established via multivariable logistic regression analysis. The performance of the model was evaluated using receiver operating characteristic curve analysis, and the area under the curve (AUC), sensitivity, specificity were calculated for the training, validation, and test sets. A nomogram was constructed for visualization, and decision curve analysis (DCA) was performed to evaluate clinical value. We included 94 eligible patients in the analysis. For each patient, we extracted a total of 1344 radiomics features. The CT combined with MR-T2WI model had the highest AUC for all sets compared to CT and MR-T2WI models. AUC values for the CT combined with MR-T2WI model in the training, validation, and test sets were 0.957, 0.901, and 0.936, respectively. DCA revealed high prediction value for the combined MR-T2WI and CT model. A radiomics model based on CT and MR-T2WI data effectively predicted LLN metastasis in rectal cancer patients preoperatively.

PET/CT imaging fibroblast activation protein in initial colorectal cancer: compared to 18 F-FDG PET/CT

OBJECTIVE

In this study, the potential advantage of FAPI over 18 F-labelled deoxyglucose ( 18 F-FDG) in evaluation of the initial staging colorectal cancer (CRC) was investigated.

MATERIALS AND METHODS

Thirty-two patients with histopathologically confirmed primary CRC were included in our study. They all underwent both 18 F-FDG and FAPI PET/CT. Lesion detectability and tracer uptakes, mainly quantified by maximum standardized uptake value (SUVmax) and target-to-background ratio (TBR), were compared for paired lesions between both modalities using the Wilcoxon signed-rank test and paired t-test.

RESULTS

Thirty-five CRC lesions in 32 patients were diagnosed. The sensitivity of FAPI PET/CT in diagnosis of the CRC lesions was 100% while 93.8% of 18 F-FDG PET/CT. FAPI and 18 F-FDG had a similar uptake in CRC lesion (mean SUVmax: 14.3 ± 8.6 vs. 15.4 ± 9.8, P  = 0.604), but lesions contained mucus and/or signet-ring cell carcinoma seemed to have a trend of higher FAPI uptake although there was no statistical difference (mean SUVmax: 12.7 ± 5.6 vs. 8.5 ± 4.1, P  = 0.152) and higher TBR (13.4 ± 6.2 vs. 4.9 ± 2.2, P  = 0.004) than those of 18 F-FDG. For regional lymph node metastases, both FAPI and FDG PET/CTs showed high sensitivity (7/8 vs. 7/8), specificity (7/8 vs. 6/8) and accuracy (14/16 vs. 13/16) (all P  > 0.05). For distant metastasis, FAPI PET/CT depicted more positive lesions in distant lymph node (46 vs. 26), liver (13 vs. 7) and peritoneum (107 vs. 45) than 18 F-FDG PET/CT. FAPI PET/CT also had a higher peritoneal cancer index score (median 11 vs 4; P  < 0.001) than 18 F-FDG PET/CT in evaluation of peritoneal metastases.

CONCLUSION

FAPI PET/CT showed high sensitivity in detection of primary CRC and superiority to 18 F-FDG PET/CT in detection of metastases to distant lymph node, liver and peritoneum.

Development of lung cancer risk prediction models based on F-18 FDG PET images

OBJECTIVE

We aimed to evaluate whether the degree of F-18 fluorodeoxyglucose (FDG) uptake in the lungs is associated with an increased risk of lung cancer and to develop lung cancer risk prediction models using metabolic parameters on F-18 FDG positron emission tomography (PET).

METHODS

We retrospectively included 795 healthy individuals who underwent F-18 FDG PET/CT scans for a health check-up. Individuals who developed lung cancer within 5 years of the PET/CT scan were classified into the lung cancer group (n = 136); those who did not were classified into the control group (n = 659). The healthy individuals were then randomly assigned to either the training (n = 585) or validation sets (n = 210). Clinical factors including age, sex, body mass index (BMI), and smoking history were collected. The standardized uptake value ratio (SUVR) and metabolic heterogeneity (MH) index were obtained for the bilateral lungs. Logistic regression models including clinical factors, SUVR, and MH index were generated to quantify the probability of lung cancer development using a training set. The prediction models were validated using a validation set.

RESULTS

The lung SUVR and lung MH index in the lung cancer group were significantly higher than in the control group (p < 0.001 and p < 0.001, respectively). In the combined prediction model 1, age, sex, BMI, smoking history, and lung SUVR were significantly associated with lung cancer development (age: OR 1.07, p < 0.001; male: OR 2.08, p = 0.015; BMI: OR 0.93, p = 0.057; current or past smoker: OR 5.60, p < 0.001; lung SUVR: OR 1.13, p < 0.001). In the combined prediction model 2, age, sex, BMI, smoking history, and lung MH index showed a significant association with lung cancer development (age: OR 1.06, p < 0.001; male: OR 1.87, p = 0.045; BMI: OR 0.93, p = 0.010; current or past smoker: OR 4.78, p < 0.001; lung MH index: OR 1.33, p < 0.001). In the validation data, combined prediction models 1 and 2 exhibited very good discrimination [area under the receiver operator curve (AUC): 0.867 and 0.901, respectively].

CONCLUSIONS

The metabolic parameters on F-18 FDG PET are related to an increased risk of lung cancer. Metabolic parameters can be used as biomarkers to provide information independent of the clinical parameters, related to lung cancer risk.

FAPI PET/CT in Diagnostic and Treatment Management of Colorectal Cancer: Review of Current Research Status

FAPI PET/CT is a novel imaging tool targeting fibroblast activation protein (FAP), with high tumor uptake rate and low background noise. Therefore, the appearance of FAPI PET/CT provides a good tumor-to-background ratio between tumor and non-tumor tissues, which is beneficial to staging, tumor description and detection. Colorectal cancer has the biological characteristics of high expression of FAP, which provides the foundation for targeted FAP imaging. FAPI PET/CT may have a potential role in changing the staging and re-staging of colorectal cancer, monitoring recurrence and treatment management, and improving the prognosis of patients. This review will summarize the application status of FAPI PET/CT in colorectal cancer and provide directions for further application research.

The Role of Preoperative Imaging in the Detection of Lateral Lymph Node Metastases in Rectal Cancer: A Systematic Review and Diagnostic Test Meta-analysis

BACKGROUND

Different techniques exist for the imaging of lateral lymph nodes in rectal cancer.

OBJECTIVE

This study aimed to compare the diagnostic accuracy of pelvic MRI, 18 F-FDG-PET/CT, and 18 F-FDG-PET/MRI for the identification of lateral lymph node metastases in rectal cancer.

DATA SOURCES

Data sources include PubMed, Embase, Cochrane Library, and Google Scholar.

STUDY SELECTION

All studies evaluating the diagnostic accuracy of pelvic MRI, 18 F-FDG-PET/CT, and 18 F-FDG-PET/MRI for the preoperative detection of lateral lymph node metastasis in patients with rectal cancer were selected.

INTERVENTIONS

The interventions were pelvic MRI, 18 F-FDG-PET/CT, and/or 18 F-FDG-PET/MRI.

MAIN OUTCOME MEASURES

Definitive histopathology was used as a criterion standard.

RESULTS

A total of 20 studies (1,827 patients) were included out of an initial search yielding 7,360 studies. The pooled sensitivity of pelvic MRI was 0.88 (95% CI, 0.85-0.91), of 18 F-FDG-PET/CT was 0.83 (95% CI, 0.80-0.86), and of 18 F-FDG-PET/MRI was 0.72 (95% CI, 0.51-0.87) for the detection of lateral lymph node metastasis. The pooled specificity of pelvic MRI was 0.85 (95% CI, 0.78-0.90), of 18 F-FDG-PET/CT was 0.95 (95% CI, 0.86-0.98), and of 18 F-FDG-PET/MRI was 0.90 (95% CI, 0.78-0.96). The area under the curve was 0.88 (95% CI, 0.85-0.91) for pelvic MRI and was 0.83 (95% CI, 0.80-0.86) for 18 F-FDG-PET/CT.

LIMITATIONS

Heterogeneity in terms of patients' populations, definitions of suspect lateral lymph nodes, and administration of neoadjuvant treatment.

CONCLUSIONS

For the preoperative identification of lateral lymph node metastasis in rectal cancer, this review found compelling evidence that pelvic MRI should constitute the imaging modality of choice. In contrast, to confirm the presence of lateral lymph node metastasis, 18 F-FDG-PET/MRI modalities allow discarding false positive cases because of increased specificity.

PROSPERO REGISTRATION NUMBER

CRD42020200319.

Role of one-step nucleic acid amplification in colorectal cancer lymph node metastases detection

Current histopathological staging procedures in colorectal cancer (CRC) depend on midline division of the lymph nodes (LNs) with one section of hematoxylin and eosin staining. Cancer cells outside this transection line may be missed, which could lead to understaging of Union for International Cancer Control Stage II high-risk patients. The one-step nucleic acid amplification (OSNA) assay has emerged as a rapid molecular diagnostic tool for LN metastases detection. It is a molecular technique that can analyze the entire LN tissue using a reverse-transcriptase loop-mediated isothermal amplification reaction to detect tumor-specific cytokeratin 19 mRNA. Our findings suggest that the OSNA assay has a high diagnostic accuracy in detecting metastatic LNs in CRC and a high negative predictive value. OSNA is a standardized, observer-independent technique, which may lead to more accurate staging. It has been suggested that in stage II CRC, the upstaging can reach 25% and these patients can access postoperative adjuvant chemotherapy. Moreover, intraoperative OSNA sentinel node evaluation may allow early CRC to be treated with organ-preserving surgery, while in more advanced-stage disease, a tailored lymphadenectomy can be performed considering the presence of aberrant lymphatic drainage and skip metastases.

Efficacy of PET/CT in diagnosis of regional lymph node metastases in patients with colorectal cancer: retrospective cohort study

Background

Endoscopic and transanal local resection without lymph node dissection are treatment options for patients with a low risk of lymph node metastasis; however, some patients might have undiagnosed lymph node metastases before surgery. This retrospective study aimed to evaluate the efficacy of preoperative PET/CT for diagnosing regional lymph node metastasis.

Methods

Patients who underwent curative resection with lymph node dissection for colorectal cancer at Osaka University between January 2012 and December 2015 were included. The cut-off values appropriate for diagnosing lymph node metastasis were calculated by way of a receiver operating characteristic (ROC) curves from maximum standard unit value (SUVmax) of main tumour, and lymph node short axis, and SUVmax of lymph node. The cut-off values of primary tumour SUVmax: 7, short-axis diameter of the lymph node at 7 mm, and lymph node SUVmax at 1.5 were set.

Result

A total of 541 patients were included. Regional lymph node metastases were confirmed in resected specimens from 187 patients (35 per cent). With a primary tumour SUVmax of 7 used as a cut-off value, the sensitivity and specificity of regional lymph node metastasis were 70.1 per cent and 45.5 per cent respectively. With a cut-off short-axis diameter of the regional lymph node of 7 mm, the sensitivity and specificity of regional lymph node metastasis were 75.2 per cent and 82.6 per cent respectively, and with a cut-off regional lymph node SUVmax of 1.5, the sensitivity and specificity of regional lymph node metastasis were 78.6 per cent and 96.8 per cent respectively. When the diagnostic criteria were defined by a lymph node short-axis diameter of 7 mm or SUVmax of 1.5, the sensitivity and specificity were 87.4 per cent and 81.8 per cent respectively.

Conclusion

Preoperative PET/CT is a useful modality for evaluating regional lymph node metastasis in patients with colorectal cancer.

Prospective study to assess the role of FDG PET/CT in detecting systemic metastatic spread in rectal cancers with lateral pelvic lymph nodes

INTRODUCTION

The utility of positron emission tomography (PET) in detecting additional M1 patients over conventional staging modalities is not known in rectal cancer patients with enlarged lateral pelvic nodes.

METHODS

Prospective, single center, single-arm interventional study of consecutive rectal cancer patients that had baseline lateral pelvic nodes on MRI (>10 mm) between February 2017 to December 2018. Such patients underwent PET after confirming non-metastatic status on CT of thorax and abdomen. Primary outcome measure was additional M1 sites detected on PET. A 10% distant metastasis rate was expected with 80% confidence interval (CI) set at 5% as the lower limit.

RESULTS

44 patients were included and the concordance between MRI and PET in detection of lateral nodes was 97.7% (43 patients). Additional sites of metastasis were detected in 5 patients (11.36%; 80% CI - 5.63%-20.6%), and there was a change in treatment plan in 7 (15.9%). The number needed to treat (NNT) for PET scans to detect additional metastatic sites and change treatment were 9 and 6 respectively. There was a change in treatment intent (curative to palliative) in 2 patients (4.5%, NNT - 22).

CONCLUSION

In rectal cancer patients with LPLN, the use of FDG-PET-CT over conventional staging studies led to the detection of additional extra-pelvic metastasis in 11.4% and changed the treatment plan in 15.9%. This met the pre-defined threshold to endorse the use of PET-CT in patients that match the study characteristics.

Residual meta-iodobenzyl guanidine (MIBG) positivity following therapy for metastatic neuroblastoma: Patient characteristics, imaging, and outcome

BACKGROUND

Meta-iodobenzylguanidine(MIBG) scans are used to detect neuroblastoma metastatic lesions at diagnosis and during posttreatment surveillance. MIBG positivity following induction chemotherapy correlates with poor outcome; however, there are reports of patients with progression-free survival despite MIBG positivity at the end of therapy. The factors distinguishing these survivors from patients who progress or relapse are unclear. FDG-positron-emission tomography (PET) scans can also detect metastatic lesions at diagnosis; however, their role in posttherapy surveillance is less well studied.

METHODS

We performed a retrospective analysis of International Neuroblastoma Staging System (INSS) stage 4 patients to identify those with residual MIBG-avid metastatic lesions on end-of-therapy scans without prior progression. Data collected included age, disease sites, histopathology, biomarkers, treatment, imaging studies, and response.

RESULTS

Eleven of 265 patients met inclusion criteria. At diagnosis three of 11 patients were classified as intermediate and eight of 11 high risk; nine of 11 had documented marrow involvement. Histologic classification was favorable for four of 10 and MYCN amplification was detected in zero of 11 cases. The median time with persistent MIBG positivity following treatment was 1.5 years. Seven patients had at least one PET scan with low or background activity. Biopsies of three of three MIBG-avid residual lesions showed differentiation. All patients remain alive with no disease progression at a median of 4.0 years since end of therapy.

CONCLUSION

Persistently MIBG-avid metastatic lesions in subsets of patients following completion of therapy may not represent active disease that will progress. Further studies are needed to determine whether MYCN status or other biomarkers, and/or PET scans, may help identify patients with residual inactive MIBG lesions who require no further therapy.

A magnetic resonance imaging (MRI)-based nomogram for predicting lymph node metastasis in rectal cancer: a node-for-node comparative study of MRI and histopathology

BACKGROUND

The aim of the present study was to investigate the potential risk factors for lymph node metastasis (LNM) in rectal cancer using magnetic resonance imaging (MRI), and to construct and validate a nomogram to predict its occurrence with node-for-node histopathological validation.

METHODS

Our prediction model was developed between March 2015 and August 2016 using a prospective primary cohort (32 patients, mean age: 57.3 years) that included 324 lymph nodes (LNs) from MR images with node-for-node histopathological validation. We evaluated multiple MRI variables, and a multivariable logistic regression analysis was used to develop the predictive nomogram. The performance of the nomogram was assessed with respect to its calibration, discrimination, and clinical usefulness. The performance of the nomogram in predicting LNM was validated in an independent clinical validation cohort comprising 182 consecutive patients.

RESULTS

The predictors included in the individualized prediction nomogram were chemical shift effect (CSE), nodal border, short-axis diameter of nodes, and minimum distance to rectal cancer or rectal wall. The nomogram showed good discrimination (C-index: 0.947; 95% confidence interval: 0.920-0.974) and good calibration in the primary cohort. Decision curve analysis confirmed the clinical usefulness of the nomogram in predicting the status of each LN. For the prediction of LN status in the clinical validation cohort by readers 1 and 2, the areas under the curves using the nomogram were 0.890 and 0.841, and the areas under the curves of readers using their experience were 0.754 and 0.704, respectively. Diagnostic efficiency was significantly improved by using the nomogram (P<0.001).

CONCLUSIONS

The nomogram, which incorporates CSE, nodal location, short-axis diameter, and minimum distance to rectal cancer or rectal wall, can be conveniently applied in clinical practice to facilitate the prediction of LNM in patients with rectal cancer.

Retrospective analysis of use of fluorine-18 fluorodeoxyglucose-positron emission tomography/computed tomography (18F-FDG PET/CT) for detection of metastatic lymph nodes in dogs diagnosed with appendicular osteosarcoma

The purpose of this retrospective analysis was to determine if fluorine-18 fluorodeoxyglucose-positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) could potentially be an accurate staging tool for detecting metastatic lymph nodes in dogs with appendicular osteosarcoma based on the quantitative measurement of the maximum standard uptake value (SUV_max) of lymph nodes. A total of 53 dogs were identified that presented for staging via ¹⁸F-FDG PET/CT for primary appendicular osteosarcoma. Patients were categorized according to lymph node status of having either metastatic or non-metastatic nodes based on cytological or histological analysis. Maximum standard uptake (SUV_max) values of the sampled lymph node(s) were recorded and 3/77 (3.9%) of sampled lymph nodes were confirmed metastatic. A Mann-Whitney test revealed a statistical difference in the SUV_max of the metastatic versus non-metastatic lymph nodes [median: 6.6 to 95% confidence interval (CI): 2.56 to 14.37 versus 2.18 95% CI: 2.32 to 3.17, respectively, P-value = 0.05]. This retrospective analysis revealed a significant difference in the SUV_max as measured on ¹⁸F-FDG PET/CT between metastatic lymph nodes and non-metastatic lymph nodes in canine patients afflicted with appendicular osteosarcoma, in spite of the small numbers analyzed. While these results are promising, they should be interpreted with caution and further studies are justified.

Pivotal role of PET/CT in characterization of occult metastasis with undetermined origin

Background

The purpose of this multicenter diagnostic accuracy test study was conducted to assess the role of positron emission tomography/computed tomography in the detection of primary tumor in cases of metastasis of undetermined primary site, to estimate its capability in detecting additional lesions as well as evaluating disease burden and staging. This multicentric diagnostic accuracy test study included 175 patients with pathologically proven, radiologically, and/or clinically suspected metastatic lesions of undetermined primary site. Clinical, surgical, and histopathologic findings and correlative imaging modalities were used to assess the results of PET/CT; the accuracy of PET/CT was expressed in terms of sensitivity and specificity, positive and negative predictive values.

Results

The study included 175 patients; PET-CT-positive lesions suggestive of primary malignant tumors were detected in 105 out of 175 patients. These lesions were pathologically proven to be malignant (true positive) in 100/175 patients (57.1%). Five out of 175 patients (2.9%) proved to be falsely positive after pathologic assessment; 70 out of 175 patients (40%) were negative for detection of primary malignancy all over the body by PET/CT (true negative) with no false negative results. PET/CT achieved a sensitivity of 100%, and specificity of 93.3% in detection of unknown primary tumor location.

Conclusion

PET/CT is an effective modality for early detection of the primary tumor site in patients with cancer of undetermined primary (CUP) which facilitates early selection of appropriate treatment protocols that will improve patients’ prognosis.

Is It Time to Introduce PET/CT in Rectal Cancer Guidelines?

At the moment, international guidelines for rectal cancer suggest to consider F-FDG PET/CT scan in a few conditions: (1) at disease presentation in case of suspected or proven metastatic synchronous adenocarcinoma with potentially curable M1 disease; (2) in the recurrence workup for serial carcinoembryonic antigen level elevation; (3) in the recurrence workup with metachronous metastases documented by CT, MRI, or biopsy; (4) in case of strong contraindication to IV contrast agent administration; and (5) to evaluate an equivocal finding on a contrast-enhanced CT or MRI. PET/CT is not indicated in the follow-up or surveillance of rectal cancer. On the other hand, an attentive evaluation of the literature shows that PET/CT may also be used in some circumstances with significant levels of diagnostic accuracy. This review article aims to emphasize differences between current international guidelines and scientific literature in the role of PET/CT in rectal cancer.

Is 18F-FDG PET/CT an Accurate Way to Detect Lymph Node Metastasis in Colorectal Cancer: A Systematic Review and Meta-Analysis

Aims

The purpose of this study was to assess the diagnostic value of ¹⁸F-fluorodeoxy-glucose positron emission tomography/computed tomography (FDG PET/CT) for detection of lymph node (LN) metastasis of colorectal cancer. Material and Methods. A computerized search was performed to determine the relevant articles, published before October 2019. Stata Statistical Software, version 15.0, and Meta-Disc (version 1.4) were used for the meta-analysis.

Results

the sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio were 0.65, 0.75, 4.57, and 0.37 respectively. Studies that used SUV_max cut-off value (≤2.5) demonstrated the best accuracy.

Conclusion

¹⁸F-FDG PET/CT shows a low sensitivity and high specificity for detecting the metastasis of LNs in patients with newly diagnosed colorectal cancer.

The Impact of Primary Tumor and Locoregional Metastatic Lymph Node SUVmax on Predicting Survival in Patients with Rectal Cancer

Objectives:

The aim of this study was to evaluate the impact of maximum standard uptake value (SUV_max) of the primary tumor and locoregional metastatic lymph node in predicting survival in patients with the preoperative rectal adenocarcinoma.

Methods:

One hundred and fifteen patients [mean age ± standard deviation (SD): 58.7±11.4 years] with biopsy-proven rectal adenocarcinoma underwent ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) imaging for the staging were included in this study. All patients were followed-up for a minimum of 12 months (mean ± SD: 29.7±13.5 months). Tumor-node-metastasis 2017 clinical staging, SUV_max of the primary rectal tumor and locoregional lymph nodes on the PET/CT studies were evaluated.

Results:

All patients had increased FDG activity of the primary tumor. The mean ± SD SUV_max of the primary tumor and locoregional metastatic lymph node were 21.0±9.1 and 4.6±2.8, respectively. Primary tumor SUV_max did not have an effect on predicting survival (p=0.525) however locoregional metastatic lymph node SUV_max had an effect (p<0.05) on predicting survival. Clinical stage of the disease was a factor predicting survival (p<0.001).

Conclusion:

¹⁸F-FDG PET/CT is an effective imaging modality for detecting primary tumors and metastases in rectal adenocarcinoma and clinical stage assessment with PET/CT had an effect on predicting survival. Furthermore, in our study locoregional lymph node SUV_maks was defined as a factor in predicting survival.

Risk factors and therapeutic significance of inguinal lymph node metastasis in advanced lower rectal cancer

PURPOSE

This study aimed to clarify predictors and therapeutic significance of inguinal lymph node metastasis (ILNM) in patients with rectal cancer.

METHODS

Patients with rectal adenocarcinoma invading the anal canal who underwent curative surgery between 2003 and 2019 were retrospectively reviewed. Synchronous and metachronous lymph node (LN) metastasis were collectively defined as final nodal metastasis (f-LNM). Factors associated with f-LNM were analyzed. Moreover, the "modified therapeutic value index," defined by multiplication of the frequency of f-LNM by the 5-year overall survival rate for patients who received treatment for f-LNM, was calculated for each LN area.

RESULTS

A total of 145 patients were enrolled (16 patients with f-ILNM). To predict f-ILNM, the cutoff of the inguinal lymph node (ILN) diameter of 8.5 mm gave an area under the curve of 0.889. Dentate line involvement (odds ratio 33.4) and ILN larger than the cutoff of 8 mm (odds ratio 11.9) were independently associated with f-ILNM. The modified therapeutic value indices of the inguinal, lateral pelvic, and mesorectal LNs in the entire population were 6.1, 8.2, and 20.3 points, respectively. In patients with dentate line invasion by cancer, the index of the ILN increased to 11.7 points. In patients with an ILN > 8 mm, the index further increased to 21.1 points.

CONCLUSION

Dentate line involvement and ILN > 8 mm predicted the development of ILNM in patients with rectal cancer invading the anal canal. Treatment of the ILN should be considered for patients with the above predictors given the significant therapeutic outcomes.

Contrast-enhanced CT imaging for the assessment of lymph node status in patients with colorectal cancer

The aim of the present study was to identify a novel strategy that predicts the metastatic status of lymph nodes (LNs) in patients diagnosed with colorectal cancer, using detailed characteristics of contrast-enhanced CT scan images. A total of 284 preoperative CT scans derived from patients diagnosed with colorectal cancer at Second Affiliated Hospital, Zhejiang University School of Medicine between January 2013 and July 2018 were retrospectively reviewed. A total of 794 LNs were assessed for size, margins, morphology and subtle internal enhancements in the equilibrium phase. Imaging features were analyzed by two abdominal radiologists (Department of Radiology, Second Affiliated Hospital, Zhejiang University School of Medicine and Departments of Radiology; Shaoxing Second Hospital Departments of Radiology, Shaoxing Second Hospital) in a blind manner. If the conclusions were not concordant, the final score was determined by a senior radiologist who specialized in abdominal radiology for ≥30 years. According to the histopathology results, 27.3% (217/794) of LNs were metastatic (LN+). In addition, LNs >10 mm in size demonstrated sensitivity, specificity, positive predictive values (PPVs) and negative predictive values (NPVs) of 47.0, 80.9, 48.1 and 80.2%, respectively [odds ratio (OR), 3.77; 95% confidence interval (CI), 2.69–5.28]. LNs in the shape of a kidney bean (middle fat depression like kidney) and/or those with an oblong shape were more likely to be metastasis negative LNs (LN-), while lobulated and irregular LNs were more likely to be LN+. In magnified images, internal enhancement characteristics of LN- were defined as homogeneous, spotted, striped and core enhancing. By contrast, rim and heterogeneity enhancement features for LN+ demonstrated sensitivity, specificity, PPVs and NPVs of 46.5, 89.9, 63.5 and 81.7%, respectively (OR, 7.79; 95% CI, 5.33–11.40). The results demonstrated that the internal enhancement features of LNs may be used as a predictor of metastasis. The detailed benign characteristics, such as homogeneity, spotted, striped and core enhancement of LNs may facilitate the identification of LN- in patients with colorectal cancer.

FDG PET/CT in colorectal cancer

Colorectal cancer is the third most frequent cancer worldwide. Although its incidence is increasing, mainly in those aged under50, mortality has decreased by 50% in the more developed countries, principally due to the adoption of new practices in prevention, diagnosis and treatment. In particular, the various diagnostic imaging modalities allow improved therapeutic decision-making, evaluation of the response and early detection of recurrence. The aim of this paper is to review the available scientific evidence on the value of positron emission tomography with ¹⁸F-FDG (¹⁸F-FDG PET/CT) in the colorectal cancer, with special emphasis on the indications of the guidelines and recommendations of the main international scientific associations regarding this imaging technique.

PET/MRI and PET/CT hybrid imaging of rectal cancer - description and initial observations from the RECTOPET (REctal Cancer trial on PET/MRI/CT) study

Purpose

The role of hybrid imaging using ¹⁸F-fluoro-2-deoxy-D-glucose positron-emission tomography (FDG-PET), computed tomography (CT) and magnetic resonance imaging (MRI) to improve preoperative evaluation of rectal cancer is largely unknown. To investigate this, the RECTOPET (REctal Cancer Trial on PET/MRI/CT) study has been launched with the aim to assess staging and restaging of primary rectal cancer. This report presents the study workflow and the initial experiences of the impact of PET/CT on staging and management of the first patients included in the RECTOPET study.

Methods

This prospective cohort study, initiated in September 2016, is actively recruiting patients from Region Västerbotten in Sweden. This pilot study includes patients recruited and followed up until December 2017. All patients had a biopsy-verified rectal adenocarcinoma and underwent a minimum of one preoperative FDG-PET/CT and FDG-PET/MRI examination. These patients were referred to the colorectal cancer multidisciplinary team meeting at Umeå University Hospital. All available data were evaluated when making management recommendations. The clinical course was noted and changes consequent to PET imaging were described; surgical specimens underwent dedicated MRI for anatomical matching between imaging and histopathology.

Results

Twenty-four patients have so far been included in the study. Four patients were deemed unresectable, while 19 patients underwent or were scheduled for surgery; one patient was enrolled in a watch-and-wait programme after restaging. Consequent to taking part in the study, two patients were upstaged to M1 disease: one patient was diagnosed with a solitary hepatic metastasis detected using PET/CT and underwent metastasectomy prior to rectal cancer surgery, while one patient with a small, but metabolically active, lung nodulus experienced no change of management. PET/MRI did not contribute to any recorded change in patient management.

Conclusions

The RECTOPET study investigating the role of PET/CT and PET/MRI for preoperative staging of primary rectal cancer patients will provide novel data that clarify the value of adding hybrid to conventional imaging, and the role of PET/CT versus PET/MRI.

Trial registration

NCT03846882.