Has PET/CT a role in the characterization of indeterminate lung lesions on staging CT in colorectal cancer? A prospective study

Management of single pulmonary metastases from colorectal cancer: State of the art

Colorectal cancer (CRC) is one of the most common causes of death from cancer. Lung seeding occurs in approximately 10% of patients surgically treated for primary CRC with radical intent: the lung is the most common site of metastases after the liver. While surgical treatment of liver metastases is widely accepted to affect long-term outcomes, more controversial and not standardized is the therapy for CRC patients developing lung metastases. Experience suggests the potential curative role of pulmonary metastasectomy, especially in oligometastatic disease. However, the optimal strategy of care and the definition of prognostic factors after treatment still need to be defined. This review focused on the uncommon scenario of single pulmonary metastases from CRC. We explored pertinent literature and provide an overview of the epidemiology, clinical characteristics and imaging of single pulmonary metastases from CRC. Additionally, we identified the best available evidence for overall management. In particular, we analyzed the role and results of locoregional approaches (surgery, radiotherapy or ablative procedures) and their integration with systemic therapy.

Dealing with indeterminate pulmonary nodules in colorectal cancer patients; a systematic review

INTRODUCTION

Indeterminate pulmonary nodules (IPNs) are frequently encountered on staging computed tomography (CT) in colorectal cancer (CRC) patients and they create diagnostic dilemmas. This systematic review and pooled analysis aims to estimate the incidence and risk of malignancy of IPNs and provide an overview of the existing literature on IPNs in CRC patients.

MATERIALS AND METHODS

EMBASE, Pubmed and the Cochrane database were searched for papers published between January 2005 and April 2020. Studies describing the incidence of IPNs and the risk of malignancy in CRC patients and where the full text was available in the English language were considered for inclusion. Exclusion criteria included studies that used chest X-ray instead of CT, liver metastasis cohorts, studies with less than 60 CRC patients and reviews.

RESULTS

A total of 18 studies met the inclusion criteria, involving 8637 patients. Pooled analysis revealed IPNs on staging chest CT in 1327 (15%) of the CRC patients. IPNs appeared to be metastatic disease during follow up in 16% of these patients. Regional lymph node metastases, liver metastases, location of the primary tumour in the rectum, larger IPN size and multiple IPNs are the five most frequently reported parameters predicting the risk of malignancy of IPNs.

CONCLUSION

A risk stratification model for CRC patients with IPNs is warranted to enable an adequate selection of high risk patients for IPN follow up and to diminish the use of unnecessary repetitive chest CT-scans in the many low risk patients.

Pitfalls and value of organ specific approach in evaluating indeterminate lesions detected on CT in colorectal cancer by [F18] FDG PET/CT

Objective

The objective of this study is to evaluate the value of FDG PET/CT for different involved organs showing Indeterminate/ equivocal / suspicious lesions detected on IV contrasted CT during surveillance follow up for colorectal cancer.

Materials and methods

A total of 67 patients with colorectal cancer how are on regular surveillance follow up by IV contrasted CT scans revealing indeterminate lesions were studied. Subsequent FDG PET/CT evaluation was performed as a problem solving modality. PET/CT results were statistically characterized when compared to biopsy results or to follow/up results. Also Statistical parameters were calculated for each organ involved. The evaluation of all CT indeterminate lesions by FDG PET/CT showed overall sensitivity of 93%, Specificity of 81%, Negative predictive value of 94%, Positive predictive value 80% and accuracy of 87%. However in an organ specific approach the highest accuracy was for lymph nodes with results showing a 100% accuracy and the lowest accuracy was for local disease at a value of 80%. Probable explanations for the falsely characterized lesions resulting in the pitfalls seen and in the imperfect accuracy were provided.

Conclusion

Study shows that FDG PET/CT is an excellent tool in characterizing CT indeterminate lesions during surveillance of colorectal cancer, However different organs showed variable accuracy results with the highest accuracy for our study was for lymph node status (100%) and the lowest accuracy being for local disease at the original site of primary tumor (80%).

Diagnostic accuracy of FDG-PET/MRI versus pelvic MRI and thoracic and abdominal CT for detecting synchronous distant metastases in rectal cancer patients

PURPOSE

We compared the diagnostic accuracy of detecting distant metastases for baseline rectal cancer staging between PET/MRI and conventional staging (CS).

MATERIALS AND METHODS

This prospective study from November 2016 to April 2018 included 101 rectal adenocarcinoma patients for primary staging. These patients underwent whole-body PET/MRI in addition to CS (pelvic MRI and thoracic and abdominal contrast-enhanced CT). Different readers analyzed CS and PET/MRI findings for primary tumor, nodal, and metastatic staging. The presence, number, and location of metastases were recorded according to the organ involved (non-regional lymph nodes (LNs), liver, lungs, or others). Lesions were defined as positive, negative, or indeterminate. The number of lesions per organ was limited to 10. The McNemar test was used to compare the accuracies.

RESULTS

PET/MRI exhibited a higher accuracy in detecting metastatic disease than CS in all patients (88.4% vs. 82.6%, p = 0.003) and in patients with extramural vascular invasion (EMVI) (88.9% vs. 85.5%, p = 0.013). The detection rate of PET/MRI was superior to that of CS for all lesions [84.1% vs. 68.9%, p = 0.001], as well as those in the liver (89.2% vs. 84.2%), non-regional LNs (90.0% vs. 36.7%), and lungs (76.4% vs. 66.9%). PET/MRI correctly classified 19/33 (57.5%) patients with indeterminate lesions on CS.

CONCLUSION

PET/MRI yields higher accuracy than CS for detecting distant synchronous metastases in the baseline staging of patients with rectal cancer and EMVI. PET/MRI exhibited a higher detection rate than CS for identifying non-regional LNs, hepatic lesions, and pulmonary lesions as well as correctly classifying patients with indeterminate lesions.

TRIAL REGISTRATION

NCT02537340.

Role of 18F-FDG PET/CT vs CT-scan in patients with pulmonary metastases previously operated on for colorectal liver metastases

OBJECTIVE

There is currently no conclusive scientific evidence available regarding the role of the ¹⁸F-FDG PET/CT for detecting pulmonary metastases from colorectal cancer (PMCRC) in patients operated on for colorectal liver metastases (CRLM). In the follow up of patients who underwent surgery for CRLM, we compare CT-scan and ¹⁸F-FDG PET/CT in patients with PMCRC.

METHODS

We designed the study prospectively performing an ¹⁸F-FDG PET/CT on all patients operated on for CRLM where the CT-scan detected PMCRC during the follow up. We included patients who were operated on for PMCRC because the histological findings were taken as a control rather than biopsies.

RESULTS

Of the 101 pulmonary nodules removed from 57 patients, the CT-scan identified a greater number (89 nodules) than the ¹⁸F-FDG PET/CT (75 nodules) (p < 0.001). Sensitivity was greater with the CT-scan (90 vs 76%, respectively) with a lower specificity (50 vs 75%, respectively) than with the ¹⁸F-FDG PET/CT. There were no differences between positive-predictive value and negative-predictive value. The ¹⁸F-FDG PET/CT detected more pulmonary nodules in four patients (one PMCRC in each of these patients) and more extrapulmonary disease in six patients (four mediastinal lymph nodes, one retroperitoneal lymph node and one liver metastases) that the CT-scan had not detected.

CONCLUSION

Although CT-scans have a greater capacity to detect PMCRC, the ¹⁸F-FDG PET/CT could be useful in the detection of more pulmonary and extrapulmonary disease not identified by the CT-scan. Advances in knowledge: We tried to clarify the utility of ¹⁸F-FDG PET/CT in the management of this subpopulation of patients.

Should preoperative chest computed tomography be performed in all patients with colorectal cancer?

AIM

This study evaluated the accuracy of chest computed tomography (CCT) in the preoperative staging of patients with potentially resectable colorectal cancer (CRC). An attempt was made to determine whether CCT has a significant influence on management and clinical outcome.

METHOD

A review was conducted of all preoperative CCTs and X-rays performed in patients submitted to elective resection of CRC at our institution between 2005 and 2012. All scans were revised by an independent radiologist who was unaware of the circumstances of each case. The findings were classified as benign, malignant or indeterminate. Patients were followed for at least 12 months after surgery to assess the clinical evolution of any lesion found on CCT and the oncological outcome.

RESULTS

Two hundred and twenty-three patients were included. The CCT showed normal or benign findings in 157 (70.4%) patients, a malignant lesion in 17 (7.6%), and an indeterminate lung lesion (ILL) in 49 (22%). Of the 30 patients with proven lung metastases, a plain X-ray detected lesions in only 11 (36.7%) patients. During the postoperative follow-up, 14 (28.6%) of the 49 patients with ILL demonstrated malignant progression of the lung lesions. Among all 223 patients, only six (2.7%) underwent lung resection.

CONCLUSION

CCT is superior to plain X-ray for the detection of lung metastases. Despite the medical and financial implications of preoperative CCT, only a small number of patients will eventually undergo lung resection. We call into question the role of routine CCT in the staging of patients with CRC. A more selective approach, reserving CT for patients at high risk of lung metastases, is suggested.