Inconsistent Findings of PET-CT Imaging in Identifying Malignancy in Cytology or Biopsy Proven Small Cell Carcinoma: A 3 Year Experience in 54 Cases.
Linh Mai Dang, Linda K Green. Baylor College of Medicine, Houston, TX; DTCL and Laboratory Medicine, Houston, TX
Background: It has become accepted that combined Positron Emission Tomography-Computerized Tomography (PET-CT) has a role in the diagnosis and prognostic staging in Non-small cell lung cancers (NSCCs) especially with standardized uptake values (SUVs) > 8 when compared to normal tissues (liver). Small cell carcinomas (SCCs) are reported to have SUVs of 8 or higher but its value in diagnosis or prognosis has been debated. We have offered PET-CT in our facility since mid-2008 and use it in lung cancer staging. We investigated its use in diagnosis and staging of small cell carcinomas of all sites.
Design: We searched our files for all cases of SCC in the lung and at distant sites diagnosed since 2008 and reviewed the clinical, radiographic, cytologic and histologic findings. PET-CT was performed using 18F-FDG PET fused with a low dose non-contrast CT scans. SUVs were reported for primary and metastatic lesions seen. The values were recorded and compared to pathologic data.
Results: There were 93 patients with small cell carcinoma and 54 patients had 1 or more PET-CT scans. SUVs of the primary tumor were as follows: 3 or less (17/31%/avg. 1.1), >3 but <6 (6/11%/avg. 4.5, >6 (29/54%/avg. 13.2) & no value (2/4%). Patients with a value >8 were 24/54 or 44%. Many metastatic lesions (cecum, rectum, lymph node, etc) had SUV's of 0.
Conclusions: PET-CT is useful in the diagnosis, staging and prognosis in NSCCs but is not as useful in small cell carcinomas. A low SUV in a lung mass does not guarantee a benign diagnosis, as seen in this study. Its value in staging may be useful with locations with high SUVs but many metastatic lesions in our study were negative. This may give a falsely low staging in SCC of lung. This may be very important in decisions of resections of limited stage SCC of the lung. Mediastinal staging with tissue diagnosis may still be of value in such patients. PET-CT is a fairly recent modality of staging and only with time and more data in pathologic correlations to reported SUV values will its use be truly determined.
Wednesday, March 2, 2011 9:30 AM
Poster Session V # 253, Wednesday Morning