FDG PET/CT in follow UP patients with colorectal carcinoma after adjuvant chemotherapy

Diagnostic Performance of F-18 FDG PET/CT in the Detection of Recurrent Colorectal Cancer: Correlation with Biochemical Markers and Conventional Imaging Modalities

Background/Objectives: Although the role of PET/CT imaging is well established in oncology, its diagnostic value in routine monitoring for recurrent colorectal cancer (CRC) is still controversial. The aim was to evaluate the diagnostic value of F-18 FDG PET/CT in detecting recurrent CRC in correlation with CEA, CA 19-9 levels, and conventional imaging modalities (CIM). Methods: Between 2009 and 2023, a retrospective study was performed including 134 CRC patients referred for PET/CT imaging on the suspicion of recurrence, based on elevated CEA and/or CA 19-9 and/or equivocal CIM findings. According to our institution's Tumor Board CRC protocol, after the initial treatment, which was dependent on the TNM stage (neoadjuvant therapy, primary resection, or adjuvant treatment), patients underwent a standard 5-year surveillance including CEA and CA 19-9 measurements, CIM, and colonoscopy, every six months. The statistics, including univariate and multivariate analyses were conducted using the IBM SPSS 20.0 statistical software. p-values < 0.05 were considered statistically significant. Results: Recurrent CRC was confirmed in 54/134 (40.3%) patients with elevated tumor markers. PET/CT showed high diagnostic performance in detecting recurrent CRC with sensitivity, specificity, PPV, NPV, and accuracy of 94.4%, 82.5%, 78.5%, 95.7%, and 87.3%, respectively. The CEA showed a high sensitivity of 98.1% but both low specificity and accuracy of 15% and 48.5%, respectively. The sensitivity, specificity, and accuracy for CA 19-9 and CIM for diagnosis of CRC recurrence were 44.4%, 67.5%, 58.2%, and 51.9%, 98.8%, 79.9%, respectively. The AUC for PET/CT, elevated CEA levels, CIM, and elevated CA 19-9 levels was 0.885 (95% CI: 0.824-0.946; p < 0.001), 0.844 (95% CI: 0.772-0.916; p < 0.001), 0.753 (95% CI: 0.612-0.844; p < 0.001), and 0.547 (95% CI: 0.442-0.652; p = 0.358), respectively. Univariate analysis showed that both PET/CT and CIM positive results were highly associated with CRC recurrence (p < 0.001 and p < 0.001, respectively). At the same time, gender, mucinous tumor type, presence of initial lymph node metastasis (N+), and presence of initial distant metastasis (M+) had no significance (p = 0.211, p = 0.158, p = 0.583, and p = 0.201, respectively). Our multivariate analysis showed that independent predictors for CRC recurrence are positive PET/CT scans (p < 0.001), positive CIM results (p = 0.001), and elevated CA 19-9 levels (p = 0.023). Although CA 19-9 was not detected as a statistically significant predictor in the univariate analysis (p = 0.358), in a multivariate analysis it was recognized as a significant predicting factor in detecting the CRC recurrence (p = 0.023). Conclusions: F-18 FDG PET/CT showed high diagnostic efficacy in CRC recurrence detection, in correlation with CEA levels, CA 19-9 levels, and CIM. This imaging modality should be routinely integrated into the post-operative follow-op in patients with elevated tumor markers.

Kolorektal kanseri olan hastaların ameliyat sonrası klinik yönetiminde fluorine-18 fluorodeoxyglucose pozitron emisyon tomografisi/bilgisayarlı tomografi’nin tanısal önemi

Amaç: Kolorektal kanser, erken tespitinde cerrahi kür sağlanabilen yaygın bir kanser türüdür. Bu kanser tipinde tedaviye yanıtın erken belirlenmesi yaşam süresini olumlu etkilemektedir. Çalışmamızda kolorektal kanseri olan hastaların, ameliyat sonrasındaki klinik yönetimlerinde F-18 FDG PET/BT’nin tanısal önemini değerlendirmeyi amaçladık. Gereç ve Yöntem: Haziran 2016 ve Ocak 2020 tarihleri arasında 168 hasta kolorektal kanser yönetimi amacıyla bölümümüze yönlendirilmiştir. Bu hastaların hepsi primer kolon tümörleri için ameliyat edilmişlerdi. Sistemik tedavi öncesinde ve sonrasında tedavi yanıtının değerlendirilmesi amacıyla bazal ve ardışık F-18 FDG PET/BT incelemesi yapılmıştır. F-18 FDG PET/BT taramaları sırasıyla analiz edilmiştir. Bulgular: Hastalar primer tümör lokalizasyonlarına göre gruplandırıldı. Toplam 168 hastanın 55’inde sağ kolonda, 33’ünde sol kolonda, 14’ünde transvers kolonda, 61’inde rektosigmoid kolonda ve 5’inde çekumda primer tümör saptandı. Lokal rekürrens 57 hastada saptanmış olup 33’ü erkek (%57.9) ve 24’ü (%42.1) kadındı. Lokal rekürrense ait ortalama SUVmaks 8.97±3.42 g/ml olarak saptandı. Ek olarak çıkan kolon grubunda 2 hastada (%1.20) yeni tümöral odak gözlendi. Sonuç: Kolorektal kanserli hastalarda, yapılabiliyorsa kolon rezeksiyonu tedavide ilk aşamadır. Küratif cerrahi sonrası ilk iki yıl içinde, hastaların yaklaşık %40’ında rekürrens görülebilmektedir. Rekürrensin erken tespiti, hastaların yaşam süresini iyileştirmektedir.