Unexpected Findings Complicate the Use of FDG-PET CT Scans : Experience of lung malignancy in One Cancer Network Anna L. Murray and Dr. Martin Walshaw (On behalf of five lung cancer MDTs in the Merseyside & Cheshire Cancer Network)

Introduction FDG-PET scans are recommended for the diagnosis and staging of lung cancer (NICE, 2005) Evidence shows that increased FDG uptake is not cancer specific and can occur in active inflammatory and healthy tissue, causing false positive results of malignancy (Chang et al., 2006) At the time of study, such incidences in a clinical population undergoing the diagnostic pathway was unknown

Aims Incidence of false positive results Service performance against agreed waiting time targets (5 days to scan and 2 days to report). Incidental left breast carcinoma in a woman with squamous cell carcinoma of the right lung

Methodology Six MDTs (Aintree, LHCH, SthPt&Orms, StHk, Wirral, Chester) 176 FDG-PET CT scans performed between February 2008 and June 2009 in diagnostic workup for lung cancer The number and site of FDG avid lesions that were not representative of lung cancer were recorded to investigate increased SUV activity. Investigation of agreed waiting time targets (five days to scan and two days to report) included the analysis of two stages: scan request to scan performance; scan performance to report availability, with regards to median and range of waiting time experienced by the network.

Results 145 scans (82%) showed non-lung cancer FDG avidity (upper gut 15 (10%), lower gut 55 (38%), thyroid 12 (8%), head and neck 58 (40%), musculoskeletal 14 (9%), others 54 (22%)): 43 (30%) at multiple sites (Figure 1) Most underwent further investigation, including upper and lower gut endoscopy, ENT examination, and MRI scans

16 (11%) additional malignancies uncovered (4 head and neck, 3 lower gut, 2 breast, 1 lymphoma, 1 thyroid, 3 prostate, and 2 ovary) In 129 (89%) the avidity was unexplained and delayed the diagnostic pathway

Median time to scan from initial request was 12 days (range 3-33) A significant group interaction was found for scan request to performance (n = 160, X2 = , p = 0.000) S ignificant differences also found pair-wise when units were compared.

Median time from scan to report was 6 days (0-21) A significant group interaction was found for scan performance to report availability (n = 170, X 2 = , p = 0.025) Significant differences found pair-wise when units were compared

Discussion 82% unexplained avidity in FDG-PET CT scans, for example upper and lower gut Led to further investigation, which delayed the diagnostic pathway Potential patient management problems (Castelluci et al., 2005) The careful assessment of FDG PET scans is necessary to ensure appropriate interpretation and accurate therapeutic decision making (Castelluci et al., 2005; Chang et al., 2006). 1. Incidence of false-positive results:

2. Service performance: Median waiting times do not reflect agreed performance levels Waiting times are highly variable Currently working with the provider to make improvements

Acknowledgements Appreciation and thanks to the following organisations, without whom the completion of this audit would not have been possible: Lung MDT, The Liverpool Heart and Chest NHS Trust Lung MDT, St. Helen’s and Knowsley Teaching Hospitals NHS Trust Lung MDT, Wirral University Teaching Hospital NHS Foundation Trust Lung MDT, Aintree University Hospitals NHS Foundation Trust Lung MDT, Southport and Ormskirk Hospital NHS Foundation Trust Lung MDT, Countess of Chester Hospital NHS Foundation Trust

References Castellucci, P.; Nanni, C.; Farsad, M.; Alinari, L.; Zinzani, P.; Stefoni, V.; Battista, G.; Valentini, D.; Pettinato, C.; Marengo, M.; Boschi, S.; Canini, R.; Baccarani, M.; Monetti, N.; Franchi, R.; Rampin, L.; Fanti, S.; Rubello, D. (2005). Potential pitfalls of 18F-FDG PET in a large series of patients treated for malignant lymphoma: prevalence and scan interpretation. Nuclear Medicine Communications, 26(8): Chang, J.M.; Lee, H.J.; Goo, J.M.; Lee H-Y; Lee, J.J.; Chung, J-K; Im, J-G (2006). False Positive and False Negative FDG-PET Scans in Various Thoracic Diseases. Korean Journal of Radiology,7:57-69 National Institute for Clinical Excellence (2005); Lung Cancer: The Diagnosis and Treatment of Lung Cancer. London: National Institute for Clinical Excellence