FDG PET/CT STAGING OF LUNG CANCER. Dr Shakher Ramdave

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1 FDG PET/CT STAGING OF LUNG CANCER Dr Shakher Ramdave

2 FDG PET/CT STAGING OF LUNG CANCER FDG PET/CT is used in all patients with lung cancer who are considered for curative treatment to exclude occult disease. FDG PET/CT is valuable in both locoregional nodal (mediastinal) and distant staging. The addition of FDG PET/CT to the conventional work-up will prevent unnecessary surgery in one out of five patients (1) and results in changing stage from that determined by conventional modalities in over half of patients (2).

3 FDG PET/CT Staging of Lung Cancer In NSCLC, FDG-PET/CT is typically acquired from the base of the skull to the proximal thighs. This field-of-view is designed to acquire data over the expected red marrow distribution, thereby covering the dominant potential sites of osseous, as well as visceral and nodal metastasis.

4 Lababede O, Chest 2011; 139:

5 TNM Staging of Lung Cancer

6 FDG PET/CT - T STAGING T classification is designed to evaluate the primary lung tumour by determining the size of the primary tumour as measured in the long-axis diameter, extent of local invasion of the primary tumour, and presence or absence of satellite nodules

7 CAN FDG PET/CT IMPROVE OVER DEDICATED CT ALONE FOR DETERMINATION OF T STAGE? Usually NO Insufficient resolution to determine size and extent of local invasion Rely on dedicated CT for this MRI not definitely better

8 The primary tumour is very difficult to visualize on CT. Corresponding PET-CT image shows nice delineation between the tumour mass and the distal atelectatic lung. RT PLANNING

9 PET/CT also improves detection of subtle areas of invasion that may be occult on CT alone. CT scan shows large right upper lobe mass that is contiguous with pleura. Appearance is suspicious for chest wall involvement but not diagnostic. PET/CT shows mild increased uptake in overlying pleural fat (arrow). Chest wall invasion was suggested and confirmed at surgery.

10 Likely T2 NSCLC on conventional staging Left vocal cord palsy indicates left recurrent laryngeal nerve involvement due to mediastinal invasion (T3)

11 N Staging Lymph node status (N staging ) is of great importance to determining the resectability of a tumour

12 CT - N Staging CT has clear shortcomings in the accurate detection of lymph node metastases. In CT a lymph node is considered to be abnormal if its short-axis diameter is more than 1 cm. However, this method has proved inaccurate. In one study, 44 % (107/405) of metastatic nodes measured <1cm, whereas an even larger percentage 77 % of patients (101/139) without metastasis had enlarged nodes measuring greater than 1 cm in the short axis.

13 PET-CT has been shown to be substantially more sensitive and specific in the detection and characterization of metastases to mediastinal lymph nodes. positive predictive value 78%, negative predictive value 91% and accuracy 87%, (superior to either modality alone).

14 FDG PET/CT - N Staging Limitations The main limitations of FDG-PET for N staging false-negative - microscopic lymph node involvement - low tumour metabolic activity false-positive - presence of infection - noninfectious inflammation LLL NSCLC - T1b Bilateral Hila and Mediastinal Nodes - Sarcoidosis

15 PET MEDIASTINAL STAGING PET POSITIVE The false positive rate of PET in the mediastinum is 13-22%. Positive PET results should be confirmed by mediastinal lymph node sampling before excluding surgery as an option. PET is useful in guiding mediastinal node sampling

16 PET MEDIASTINAL STAGING PET NEGATIVE The false negative rate of PET in the mediastinum is 5 to 8% for a peripheral tumour compared with an average false-negative rate for invasive mediastinal staging of 9%. Invasive mediastinal staging can potentially be avoided before thoracotomy if PET is negative in a <1cm node.

17 PET MEDIASTINAL STAGING META-ANALYSIS In a meta-analysis of 14 studies of patients with NSCLC, de Langen and colleagues reported that the likelihood for malignancy in an FDG nonavid lymph node was 5% when 10 to 15 mm in diameter 21% when > 15 mm, whereas the likelihood for an FDG avid node was 62% when 10 to 15 mm 90% when > 15 mm.

18 STAGING OF LUNG CANCER M STAGE M1a (Intra-thoracic Metastases) Malignant pleural or pericardial effusion, malignant pleural nodules, or satellite nodules in contralateral lung M1b (Distant Metastases) Metastasize to almost every organ but mainly to brain, adrenals, bone, liver and distant nodes.

19 STAGING OF LUNG CANCER M STAGE FDG PET/CT detected occult extrathoracic metastases in upto 24% of patients selected for curative resection Lung Cancer Upstaged from M0 to M1b Bony, Adrenal and Liver Metastases on PET/CT MacManusMP,HicksRJ,MatthewsJP,etal: High rate of detection of unsuspected distant metastases by pet in apparent stageiii non small-cell lung cancer: Implications for radical radiation therapy. Int JRadiatOncol Biol Phys50(2): , 2001

20 BONE /MARROW METASTASES Bone metastasis is present in 20%-30% of patients at the initial diagnosis of lung cancer. FDG PET Sensitivity 92%, specificity 98%. Compared with bone scan, FDG PET/CT is equal or greater in sensitivity and more specific for the diagnosis of bone marrow metastases from lung cancer. FDG-PET/CT can detect metastases before destruction of bone has occurred. Qu X, Huang X, Yan W, et al. A meta-analysis of (18)FDG-PET-CT, (18)FDG-PET, MRI and bone scintigraphy for diagnosis of bone metastases in patients with lung cancer. Eur J Radiol 2012; 81(5):

21 BONE / MARROW METASTASES Tc 99m MDP Bone Scan NaF PET/CT Bone Scan Bone scan has reduced sensitivity in lytic bony metastases

22 ADRENAL METASTASES Right adrenal adenoma Adrenal metastases are detected in upto 20% of patients with NSCLC. CT has a reported sensitivity, specificity, and accuracy of 60%,80%,and77%, respectively. Left adrenal metastasis FDG-PET/CT is more accurate in detecting adrenal metastases. In a meta-analysis that included 1391 lesions (824 benign and 567 malignant), FDG-PET had a reported sensitivity and a specificity of 97% and 91%,respectively.

23 BRAIN METASTASIS MRI of the brain remains the method of choice for detecting cerebral metastasis. Contrast-enhanced CT is the most commonly performed procedure in search of brain metastases in spite of the fact that MRI with contrast injection has a greater sensitivity than CT. PET- Sensitivity 60%. Cannot substitute dedicated CT or MRI.

24 STAGING OF NSCLC PET/CT/MRI T2N1 on CT T2M1b on PET/CT + MRI

25 Metastatic disease identified by PET requires additional confirmation particularly if there is a single lesion T1a N0?M1b NSCLC Left adrenal Phaeochromocytoma

26 PET/CT STAGING OF LUNG CARCINOID Neuroendocrine tumours vary in differentiation and glucose metabolism Ga 68-DOTATATE PET/CT 22 Aug 2014 F-18 FDG PET/CT 11 Aug 2014

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