| Objective: The aim of this study were:⑴to determine whether the use of 18F-fluoro-2-deoxy-D-glucose (18F-FDG) positron emission tomography/ computed tomography (PET/CT) alters staging and management of nasopharyngeal carcinoma (NPC) when compared with current staging practice;⑵to explore the relation of standard uptake value (SUV) of 18F-FDG PET/CT and the pathological classification and clinical staging of nasopharyngeal carcinoma (NPC).Methods: The study was performed retrospectively on a group of 41 patients (25 males, 16 females; mean age, 52.3; age range, 14-72 years) from Catholic University Kangnum St. Mary's hospital of Korea with a new diagnosis of nasopharyngeal carcinoma confirmed by histology. All patients underwent CT and MRI of the head and neck and a whole-body 18F-FDG PET/CT scan. The three examinations were performed within 3 weeks. Tumor stage was determined according to the 6th edition of the American Joint Committee on Cancer (AJCC) classification. The scans were compared for extent of the primary tumor (PT), cervical nodal metastases (CNM) and distant metastases (DM). For PET/CT, the region of interest (ROI) covering the pharyngeal lesions were defined along the margins of the lesion, and the lesion SUVs were calculated. FDG accumulation was scored, as follow: 0, normal; 1, probably normal; 2, equivocal; 3, probably abnormal; 4, definitely abnormal. The MRI and CT were analyzed separately by an experienced radiologist who did not know the FDG-PET results. FDG-PET images with a score of 3 or 4 were defined as positive and those with a score of 0-2 as negative. A positive score on either the 40-min or 3-h scan was considered positive. The presence or absence of disease was determined by pathologic evaluation and other examinations. On CT and MRI, cervical lymph nodes were considered as metastatic according to criteria regarding size, the presence of nodal necrosis, and extracapsular spreads. FDG PET images were interpreted visually, and nodes were considered metastatic if they showed prominent FDG uptake against the background.Results: 1. Primary Tumor①Any discordance in results was assessed with respect to staging and impact on management grades. MRI and PET/CT scans were discordant in 30 sites in 17 patients. Significant discrepancies were found for tumors involving the nasal cavity, oropharynx, parapharyngeal space and paranasal sinus. According to MRI findings, the T stages of our 41 patients were as follows: T1, 30 patients; T2a 10 patients; T2b 4 patients; T3 2 patients; T4 5 patients. PET/CT altered T staging in 17 patients (41.5%). Specifically, 12 patients (29.3%) were downstaged and 5 (12.2%) were upstaged.②The SUVs in stage I, II, III and IV patients were 4.28±0.38, 7.13±1.38, 7.66±1.50, 8.63±1.35, respectively, showing no significant differences between them(P>0.05). In patients in stage T1, T2, T3 and T4, the SUVs increased significantly in advanced grades (2.42±1.10, 3.90±0.57, 7.10±1.02, 9.70±0.58, respectively, P<0.05 ). The SUVs in poorly differentiated squamous carcinoma was significantly lower than that in undifferentiated carcinoma (4.87±1.07 vs 8.37±1.69, respectively, F=1.336,P=0.01) . 2. Lymph Nodes Metastases①Among our 41 patients with NPC, nodal metastasis shown on MRI and FDG PET were in 31 patients, and 30 patients were confirmed to be positive. MRI suggested metastatic lesions but FDG PET suggested benign nodes in 29 cervical nodal lesions. Fine-needle aspiration of these 29 cervical nodal lesions revealed 22 to be benign and 7, metastatic. On the other hand, FDG PET suggested a benign process but MRI suggested metastatic nodes in 39 regional nodal lesions. Fine-needle aspiration of these nodes yielded positive findings for metastasis in all except four of the lesions. PET/CT altered N staging in 8 patients (19.5%). Specifically, 4 patients (9.8%) were downstaged and 4 (9.8%) were upstaged.②Among the 30 patients with nodal metastasis, involvement was bilateral in 15(50%)and unilateral in 5(50%). 15 patients had primary tumors sited in the middle of the nasophrynx; of the 26 who did not. Of the 15 patients with tumors involving the midline, 10 had bilateral lymph nodes involvement and 8, unilateral involvement. Of the 26 patients with nasopharyngeal tumors without midline crossing, 5 showed bilateral nodal metastases and 7, unilateral nodal metastasis(6, ipsilateral nodal metastasis; 1, contralateral nodal metastasis). 3. Distant Metastases:Among the 41 patients, 2 patients with liver and bone metastases were detected by FDG-PET, which missed by MRI.Conclusion:⑴There is discordance between MRI and 18F-FDG PET/CT, and additional use of 18F-FDG PET/CT for the current assessment of NPC at diagnosis appear to be justified in this cohort of patients.⑵The SUV is not associated with the clinical staging of NPC, but is correlated to the T staging of NPC, and also related to the pathological classification. |
PDF Full Text Request