Role of Fluorodeoxyglucose-Positron Emission Tomography/Computed Tomography in the Evaluation of Head and Neck Carcinoma

Positron Emission Tomography With Fluorodeoxyglucose Incidental Detection of Colon Cancer in a Patient's Follow-Up for Nasopharyngeal Carcinoma During the COVID-19 Pandemic: A Case Report

Colorectal cancer (CRC) is a type of widespread, deadly malignancy that took thousands of lives around the globe. In the last two decades, CRC represented the most common cancer among men and ranked third among women in Saudi Arabia. Positron emission tomography with fluorodeoxyglucose (FDG-PET), can incidentally detect malignancy, as in our case, FDG-PET disclosed high abnormal FDG far away from the first primary malignancy. The current case is of a 65-year-old female who was following up on her nasopharyngeal carcinoma (first primary). During her last management, FDG-PET was requested to find any FDG uptake in the nasopharyngeal region; stunning FDG uptake was incidentally found at the ascending colon diagnosed as early-stage (pT2N0) colon cancer. Colonoscopy was done and India Ink was injected to facilitate localizing the mass during the laparoscopic removal of the tumor, which was delayed due to the pandemic of COVID-19. This took place in March 2020 at King Abdul-Aziz University Hospital in Jeddah.

PET/CT in Surgical Planning for Head and Neck Cancer

Fluorine-18 (¹⁸F)-fluorodeoxyglucose (FDG) positron emission tomography fused with computed tomography (PET/CT) is a valuable tool in surgical planning for head and neck squamous cell carcinoma (HNSCC). If performed prior to biopsy or other surgical intervention, FDG-PET/CT has high sensitivity for the detection of the primary site in patients with cervical lymph node metastases from unknown primary origin and can be used to direct the surgical workup. FDG-PET/CT is superior to CT alone for detection of nodal metastases outside the expected pattern or distant metastases or second primary cancers and can greatly affect determination of appropriate management including surgical eligibility. Prior to the advent of PET/CT, many patients undergoing (chemo)radiation-based therapy had planned post-treatment neck dissection; FDG-PET/CT now has a proven role in the evaluation of recurrent or persistent disease amenable to salvage surgery and enables safe avoidance of planned postradiation neck dissection with a high negative predictive value. Specifically for this important application, two standardized reporting metrics may be used in the head and neck anatomic region: the "Hopkins criteria" and the "Neck Imaging Reporting and Data System"; both systems produce a formalized evaluation and recommendation based on PET/CT findings. The role of PET/CT as a replacement for elective neck dissection or examination under anesthesia remains controversial but deserves further study. FDG-PET/CT has a wide-ranging impact on the surgical management of patients with HNSCC and should be used routinely in patients with unknown primary nodal disease and those presenting with advanced-stage cancers at initial staging and to assess treatment response.

FDG PET Hybrid Imaging

Molecular imaging with positron emission tomography (PET) using tumour-seeking radiopharmaceuticals has gained wide acceptance in oncology with many clinical applications. The hybrid imaging modality PET/CT (computed tomography) allows assessing molecular as well as morphologic information at the same time. Therefore, PET/CT represents an efficient tool for whole-body staging and re-staging within one imaging modality. In oncology, the glucose analogue 18-F-fluorodeoxyglucose (FDG) is the most widely used PET/CT radiopharmaceutical in clinical routine. FDG PET and FDG PET/CT have been used for staging and re-staging of tumour patients in numerous studies. This chapter will discuss the use and the main indications of FDG PET/CT in oncology with special emphasis on lung cancer, lymphoma, head and neck cancer, melanoma and breast cancer (among other tumour entities). A review of the current literature is given with respect to primary diagnosis, staging and diagnosis of recurrent disease. Besides its integral role in diagnosis, staging and re-staging of disease in oncology, there is increasing evidence that FDG PET/CT can be used for therapy response assessment (possibly influencing therapeutic management and treatment planning) by evaluating tumour control, which will also be discussed in this chapter.

The Effect of Carbogen Breathing on 18F-FDG Uptake in Non-Small-Cell Lung Cancer

It has been reported that ¹⁸F-FDG uptake is higher in hypoxic cancer cells than in well-oxygenated cells. We demonstrated that ¹⁸F-FDG uptake in lung cancer would be affected by high concentration oxygen breathing. Methods. Overnight fasted non-small-cell lung cancer A549 subcutaneous (s.c.) xenografts bearing mice (n = 10) underwent ¹⁸F-FDG micro-PET scans, animals breathed room air on day 1, and same animals breathed carbogen (95% O₂ + 5% CO₂) on the subsequent day. In separated studies, autoradiography and immunohistochemical staining visualization of frozen section of A549 s.c. tumors were applied, and to compare between carbogen-breathing mice and those with air breathing, a combination of ¹⁸F-FDG and hypoxia marker pimonidazole was injected 1 h before animal sacrifice, and ¹⁸F-FDG accumulation was compared with pimonidazole binding and glucose transporter 1 (GLUT-1) expression. Results. PET studies revealed that tumor ¹⁸F-FDG uptake was significantly decreased in carbogen-breathing mice than those with air breathing (P < 0.05). Ex vivo studies confirmed that carbogen breathing significantly decreased hypoxic fraction detected by pimonidazole staining, referring to GLUT-1 expression, and significantly decreased ¹⁸F-FDG accumulation in tumors. Conclusions. High concentration of O₂ breathing during ¹⁸F-FDG uptake phase significantly decreases ¹⁸F-FDG uptake in non-small-cell lung cancer A549 xenografts growing in mice.

Evaluation of Iodine-125 Interstitial Brachytherapy Using Micro-Positron Emission Tomography/Computed Tomography with 18F-Fluorodeoxyglucose in Hepatocellular Carcinoma HepG2 Xenografts

BACKGROUND Iodine-125 interstitial brachytherapy (125I-IBT) is a promising treatment option for unresectable hepatocellular carcinoma (HCC). This study evaluated the usefulness of micro-positron emission tomography/computed tomography (micro-PET/CT) with 18F-fluorodeoxyglucose (18F-FDG) in assessing response to 125I-IBT in HCC HepG2 xenograft. MATERIAL AND METHODS Twelve mice with bilateral HepG2 xenografts were divided into 3 equal groups implanted with iodine-125 seeds into the left xenografts with a dose of 30, 50, and 80 Gy, respectively, and the right xenografts were used as internal controls. Before and 28 days after treatment, the 18F-FDG micro-PET/CT was performed. The ratios of left to right xenografts of tumor volume (RTV), maximum standardized uptake value (RSUVmax), mean optical density of caspase-3 expression (RMODcaspase-3), and apoptosis index (RAI) were compared. RESULTS The RTV means of the 50 and 80 Gy groups were significantly lower than in the 30 Gy group after treatment (P<0.01) and the RTV means after treatment were lower than baseline in the 50 and 80 Gy groups (P<0.05). The RSUVmax mean after treatment was lower than baseline in the 80 Gy group (P<0.05). The RMODCaspase-3 and RAI means of the 80 Gy group were higher than in the 30 Gy group (P<0.05). The RSUVmax was correlated negatively to RMODcaspase-3 (r=-0.624, P<0.05) and RAI (r=-0.651, P<0.05). CONCLUSIONS This study suggest that 125I-IBT inhibits tumor growth via upregulating caspase-3 expression and prompting apoptosis in HCC HepG2 xenografts. The 18F-FDG micro-PET/CT may be a useful functional imaging modality to assess early response to 125I-IBT in HCC HepG2 xenograft.