Assessment of extra-parenchymal lung involvement in asymptomatic cancer patients with COVID-19 pneumonia detected on 18F-FDG PET-CT studies.

BACKGROUND: Lung involvement in patients with coronavirus disease 2019 (COVID-19) undergoing PET-CT has been previously reported. However, FDG uptake outside lung parenchyma was poorly characterized in detail. We evaluated the extra-parenchymal lung involvement in asymptomatic cancer patients with COVID-19 pneumonia through 18F-FDG PET-CT. METHODS: A total of 1079 oncologic 18F-FDG PET-CT were performed between February 2 and May 18, 2020. Confirmed COVID-19 pneumonia was defined as characteristic ground-glass bilateral CT infiltrates and positive genetic/serologic tests. Nonmetastatic extra-parenchymal lung PET-CT findings were evaluated through qualitative (visual), quantitative (measurements on CT), and semiquantitative (maximum standardized uptake value: SUVmax on PET) interpretation. Clinical data, blood tests, and PET-CT results were compared between patients with and without COVID-19 pneumonia. RESULTS: A total of 23 18F-FDG PET-CT scans with pulmonary infiltrates suggestive of COVID-19 and available laboratory data were included: 14 positive (cases) and 9 negative (controls) for COVID-19 infection, representing a low prevalence of COVID-19 pneumonia (1.3%). Serum lactate dehydrogenase and D-dimers tended to be increased in COVID-19 cases. Extra-parenchymal lung findings were found in 42.9% of patients with COVID-19, most frequently as mediastinal and hilar nodes with 18F-FDG uptake (35.7%), followed by incidental pulmonary embolism in two patients (14.3%). In the control group, extra-pulmonary findings were observed in a single patient (11.1%) with 18F-FDG uptake located to mediastinal, hilar, and cervical nodes. Nasopharyngeal and hepatic SUVmax were similar in both groups. CONCLUSION: In cancer patients with asymptomatic COVID-19 pneumonia, 18F-FDG PET-CT findings are more frequently limited to thoracic structures, suggesting that an early and silent distant involvement is very rare. Pulmonary embolism is a frequent and potentially severe finding raising special concern. PET-CT can provide new pathogenic insights about this novel disease.

Tumor burden monitoring using cell-free tumor DNA could be limited by tumor heterogeneity in advanced breast cancer and should be evaluated together with radiographic imaging.

BACKGROUND: Accurate measurement of tumor burden in breast cancer disease is essential to improve the clinical management of patients. In this study, we evaluate whether the fluctuations in the fraction of PIK3CA mutant allele correlates with tumor response according to RECIST criteria and tumor markers quantification. METHODS: Eighty six plasma samples were analyzed by digital PCR using Rare Mutation Assays for E542K, E545K and H1047R. Mutant cfDNA and tumor markers CA15-3 and CEA were compared with radiographic imaging. RESULTS: The agreement between PIK3CA mutation status in FFPE samples and circulating tumor DNA (ctDNA) was moderate (K = 0.591; 95% IC = 0.371-0.811). Restricting the analysis to the metastatic patients, we found a good agreement between PIK3CA mutation status assessed in liquid and solid biopsy (K = 0.798 95%; IC = 0.586-1). ctDNA showed serial changes with fluctuations correlating with tumor markers 15.3 and CEA in 7 out of 8 cases with Pearson correlation coefficients ranging from 0.99 to 0.46 and from 0.99 to 0.38 respectively. Similarly, fluctuations in the fraction of PIK3CA mutant allele always correlated with changes in lesion size seen on images, although in two cases it did not correlate with treatment responses as defined by RECIST criteria. CONCLUSION: oncogenic mutation quantification in plasma samples can be useful to monitor treatment outcome. However, it might be limited by tumor heterogeneity in advanced disease and it should be evaluated together with radiographic imaging.

Incidental Findings Suggestive of COVID-19 Pneumonia in Oncologic Patients Undergoing 18F-FDG PET/CT Studies: Association Between Metabolic and Structural Lung Changes.

Although the novel coronavirus disease 2019 (COVID-19) can present as nonspecific clinical forms, subclinical cases represent an important route of transmission and a significant source of mortality, mainly in high-risk subpopulations such as cancer patients. A deeper knowledge of the metabolic shift in cells infected with severe acute respiratory syndrome coronavirus 2 could provide new insights about its pathogenic and host response and help to diagnose pulmonary involvement. We explored the potential added diagnostic value of 18F-FDG PET/CT scans in asymptomatic cancer patients with suspected COVID-19 pneumonia by investigating the association between metabolic and structural changes in the lung parenchyma. Methods:18F-FDG PET/CT studies acquired between February 19 and May 29, 2020, were reviewed to identify those cancer patients with incidental findings suggestive of COVID-19 pneumonia. PET studies were interpreted through qualitative (visual) and semiquantitative (measurement of SUVmax) analysis evaluating lung findings. Several characteristic signs of COVID-19 pneumonia on CT were described as COVID-19 Reporting and Data System (CO-RADS) categories (1-6). After comparing the SUVmax of pulmonary infiltrates among different CO-RADS categories, we explored the best potential cutoffs for pulmonary SUVmax against CO-RADS categories as the gold standard result to eliminate the possibility that the diagnosis of COVID-19 pneumonia exists. Results: On multimodal PET/CT imaging, CT signs classified as CO-RADS category 5 or 6 were found in 16 of 41 (39%) oncologic patients. SUVmax was higher in patients with categories 5 and 6 than in patients with category 4 (6.17 ± 0.82 vs. 3.78 ± 0.50, P = 0.04) or categories 2 and 3 (3.59 ± 0.41, P = 0.01). A specificity of 93.8% (95% CI, 71.7%-99.7%) and an accuracy of 92.9% were obtained when combining a CO-RADS score of 5 or 6 with an SUVmax of 2.45 in pulmonary infiltrates. Conclusion: In asymptomatic cancer patients, the metabolic activity in lung infiltrates is closely associated with several combined tomographic changes characteristic of COVID-19 pneumonia. Multimodal 18F-FDG PET/CT imaging could provide additional information during early diagnosis in selected predisposed patients during the pandemic. The prognostic implications of simultaneous radiologic and molecular findings in cancer patients and other subpopulations at high risk for COVID-19 pneumonia deserve further evaluation in prospective research.

Evaluation of tumor response after stereotactic body radiation therapy for lung cancer: Role of 18F-fluorodeoxyglucose positron emission tomography/computed tomography.

BACKGROUND: Early identification of patients who fail to lung stereotactic body radiation therapy (SBRT) is vital as they can benefit from salvage therapy. Main guidelines recommend computed tomography (CT) to assess response and use of 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/CT only when a local recurrence is suspected in CT. The pattern of radiation-induced lung injury caused by SBRT is different from changes seen after conventional radiation therapy in terms of extent, time of manifestation, and morphologic characteristics, and knowing this is crucial for proper monitoring of the tumor response. In certain cases, it may be difficult to differentiate response from progression or recurrence on CT and, in addition, some changes in CT take a long time to evolve before they are considered suspicious, making early diagnosis difficult. Metabolic changes often precede morphological changes, so 18F-FDG PET/CT quantitative and qualitative metabolic criteria can be useful in assessing early response and detecting relapses. However, the optimal practice for follow-up remains unclear and there is an active search for imaging markers for recurrent disease, including CT texture analysis, biomarker assays, new PET/CT isotopes, and magnetic resonance imaging. AIM: The aim of the study was to review the radiological changes that are objectified after pulmonary SBRT and the metabolic changes in 1F-FDG PET/CT, to assess the usefulness of following up patients with 18F-FDG PET/CT. RELEVANCE FOR PATIENTS: At present, the evaluation of response and diagnosis of relapse after SBRT are difficult and the incorporation of routine 18F-FDG PET/CT may have value in early diagnosis of relapse when the patient may still benefit from rescue treatment.

Predictive value of PET-CT for pathological response in stages II and III breast cancer patients following neoadjuvant chemotherapy with docetaxel.

PURPOSE: To prospectively study the value of PET-CT with fluorine-18 fluorodeoxyglucose (FDG) to predict neoadjuvant chemotherapy (NAC) response of locoregional disease of stages II and III breast cancer patients. MATERIAL AND METHODS: A written informed consent and approval were obtained from the Ethics Committee. PET-CT accuracy in the prediction of pathologic complete response (pCR) after NAC was studied in primary tumors and lymph node metastasis in 43 women (mean age: 50 years: range: 27-71 years) with histologically proven breast cancer between December 2009 and January 2011. PET-CT was performed at baseline and after NAC. SUV(max) percentage changes (ΔSUV(max)) were compared with pathology findings at surgery. Receiver-operator characteristic (ROC) analysis was used to discriminate between locoregional pCR and non-pCR. In patients not achieving pCR, it was investigated if ΔSUV(max) could accurately identify the residual cancer burden (RCB) classes: RCB-I (minimal residual disease (MRD)), RCB-II (moderate RD), and RCB-III (extensive RD). RESULTS: pCR was obtained in 11 patients (25.6%). Residual disease was found in 32 patients (74.4%): 16 (37.2%) RCB-I, 15 (35.6%) RCB-II and 2 (4.7%) RCB-III. Sensitivity, specificity, and accuracy to predict pCR were 90.9%, 90.6%, and 90.7%, respectively. Specificity was 94.1% in the identification of a subset of patients who had either pCR or MRD. CONCLUSION: Accuracy of ΔSUV(max) in the locoregional disease of stages II and III breast cancer patients after NAC is high for the identification of pCR cases. Its specificity is potentially sufficient to identify a subgroup of patients who could be managed with conservative surgery.