Prospective study on diagnostic and prognostic significance of postoperative FDG PET/CT in recurrent colorectal carcinoma patients: comparison with MRI and tumor markers.

Current guidelines for follow-up after resection of colorectal cancer (CRC) recommend regular measurements of carcinoembryogenic antigen (CEA) and imaging tests. Multidetector computed tomography (MDCT) and magnetic resonance imaging (MRI) are currently primary imaging modalities, while the role of fluorine-18-fluoro-deoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT), which is recommended in patients with negative MDCT and increased CEA, is still uncertain. Our aim was to compare diagnostic performance and prognostic significance of 18F-FDG PET/CT with MRI and tumor markers CEA and carbohydrate antigen 19-9 (CA 19-9) in detection of recurrent CRC. This prospective study included 35 patients with resected CRC, referred to 18F-FDG PET/CT examination for suspected recurrence. During median follow-up of 24.4±1.5 months 18F-FDG PET/CT and MRI results and tumor marker levels were compared with findings of histopathological examination or with results of clinical and imaging follow-up. Management plan before the 18F-FDG PET/CT scan was considered and compared to the final treatment decision. The sensitivity, specificity, positive and negative predictive value and accuracy of 18F-FDG PET/CT and MRI in detection of recurrent colorectal cancer in patient-based analysis were 92.6%, 75%, 92.6%, 75% and 88.6%, and 65.4%, 66.7%, 85%, 40% and 65.7%, respectively. In lesion-based analysis the sensitivity of 18F-FDG PET/CT and MRI was 83.1% and 68.2%, respectively. The overall accuracy of CEA and CA 19-9 in recurrence detection was 48.6% and 54.3%, respectively. PET/CT induced therapy alterations in 13/35 (37.1%) patients. Progression was observed in 16/35 patients during follow-up, with significantly lower risk of progression in patients with treatment changes based on PET findings (Multivariate Cox regression; p=0.017). In addition, elevated CA 19-9 levels in time of PET scan and male gender carried significantly higher risk of progression (p=0.007 and p=0.016, respectively). Kaplan-Meier Log rank test showed significantly longer progression-free survival time in patients who had treatment plan changed based on PET/CT (p=0.046). We can conclude that 18F-FDG PET/CT showed better sensitivity and accuracy compared to MRI in detection of recurrent colorectal cancer, with much better sensitivity compared to CEA and CA 19-9. Patients with treatment changes based on 18F-FDG PET/CT had significantly better prognosis and longer progression-free survival, while elevated values of CA 19-9 and male gender were associated with worse prognosis.

Metabolic activity of breast cancer metastatic lesions on positron emission tomography/computed tomography: comparison with histological and biological characteristics of primary tumor.

Higher intensity of FDG uptake on PET/CT in primary tumor is seen in patients with IDC compared to ILC, also in high grade tumours, tumours with negative ER and higher Ki67 values, while data are inconsistent in case of relation between primary tumor's PgR and HER2 expression with its metabolic activity levels. On account of the lack of studies that include research of breast cancer metastatic lesion metabolism level and its relation to tumor histology and biology, our goal was to investigate the association of metastatic lesions' glucose metabolism level on PET/CT with different histological and biological characteristics of primary tumor. In a total number of N=100 patients, highest SUVmax values for each patient were used in testing difference between metastatic metabolic activity in patients with different tumor histology, grade, ER, PgR and HER2 status, subtype, as well in testing relation of Ki67 index to metastasis' metabolism level. In testing difference between histological types of breast cancer, SUVmax values were also compared separately for each specific anatomical site (regional and distant lymph nodes, bones and liver). No difference was found regarding metastatic SUVmax values in patients with primary IDC (n=55, median SUVmax 9.70) and ILC (n=34, median SUVmax 7.20) independently of anatomic site, and for each of analysed sites separately. No difference was found as well between SUVmax detected in metastasis in patients with different grade (grade II: n=58, median SUVmax 7.70; grade III: n=12, median SUVmax 10.20), ER (59 positive, median SUVmax 8.50; 22 negative, median SUVmax 8.05), PgR (55 positive, median SUVmax 8.50; 23 negative, median SUVmax 7.80), and HER2 (14 positive, median SUVmax 6.84; 51 negative, median SUVmax 8.63) expression in primary tumor, and between patients with different tumor subtype. Ki67 was also not associated with tumor metastatic SUVmax values (n=11, rs = -0.21, p=0.53). We conclude that there is no association of primary breast cancer histological type, grade, ER, PgR, HER2 and Ki67 expression with metabolic activity in metastasis detected on PET/CT.

Comparison of 18F-FDG PET/CT and MDCT for staging/restaging of non-small cell lung cancer.

UNLABELLED: Multi-detector computed tomography (MDCT) is most commonly used for staging of non-small cell lung cancer (NSCLC). In recent years, 18F- fluorodeoxyglucose positron emission tomography combined with computed tomography (18F-FDG PET/CT) has also been used for the same purpose. Since studies comparing these two methods are scarce, our aim was to determine how the TNM classification and thereby staging of NSCLC compare between 18F-FDG PET/CT and MDCT. 18F-FDG PET/CT and MDCT were collected in 83 patients with NSCLC 3 to 30 days apart (median 17 days). The investigators interpreting 18F-FDG PET/CT were unaware of MDCT results. The Cohen's kappa (κ) was calculated to determine the rate of agreement. The hypothesis was that the strength of agreement between the two methods will be at least moderate (κ>0.40) based on the adopted criteria (κ<0.20 poor; 0.21-0.40 fair; 0.41-0.60 moderate; 0.61-0.80 good; 0.81-1.00 very good agreement). The agreement was moderate for determining the T class (κ=0.45, overall agreement 58%), poor for the N class (κ=0.13, 42%) and fair for the M class (κ=0.22, 58%). The agreement for overall staging of NSCLC was poor (κ=0.20, 45%). The major source of disagreement was that metastases were present more frequently and/or in larger number on 18F-FDG PET/CT than MDCT in the contralateral mediastinal, supraclavicular, and distant lymph nodes, as well as in the bones and suprarenal glands. Since 18F-FDG PET/CT detected more regional and distant metastases than MDCT, we conclude that FDG PET/CT is useful for staging/restaging and planning treatment of patients with NSCLC. KEYWORDS: Non-small cell lung cancer, positron emission tomography, multidetector computed tomography, metastases detection.