Abstract
P275
Introduction: Peptide- and amine-producing neuroendocrine cells are thought to form pulmonary neuroendocrine tumors (NETs), with the majority having somatostatin (SSRTR) type 2 receptors. Gallium-68 (Ga-68) DOTATATE, a radiologically active agent, has a higher affinity with the somatostatin cells, specifically SSTR2 receptors. This allows tumors that express SSTR2 receptors to be detected with a high yield on positron emission tomography (PET) imaging. Ga-68 DOTATATE PET has been considered superior to Fluorodeoxyglucose (FDG) PET in the detection of pulmonary neuroendocrine tumors. We sought to determine the sensitivity of the Ga-68 DOTATATE PET scan in detecting primary pulmonary NETs and nodal metastasis to establish the carcinoid stage and its utility in evaluating the histological type of pulmonary carcinoid.
Methods: We performed a retrospective study to evaluate the patients treated at Mayo Clinic in Rochester from January 2017 to June 2022. We collected clinical, cytopathological, and radiological data of all the patients who underwent surgical resection of pulmonary carcinoid.
Results: A total of 195 patients underwent surgical resection for pulmonary neuroendocrine tumors. We excluded the patients who received Ga-68 DOTATATE PET after the surgery and those diagnosed with a large cell metastatic neuroendocrine tumor. Forty-four patients (23%) had Ga-68 DOTATATE PET before surgery. Among the 44 patients, 17 (39%) and 27 (61%) were male and female, respectively. 32% of these patients had a smoking history with a mean of 12 pack years. The median age of diagnosis of primary pulmonary NETs was 55 years (range 16 to 83 years).
The distribution of histologically classified primary pulmonary carcinoids was 31 (66%) typical carcinoids (TC) and 13 (34%) atypical carcinoids (AC). The primary tumor was Ga-68 DOTATATE positive in 40 patients. The sensitivity of Ga-68 DOTATATE PET in detecting pulmonary carcinoids was 91%, and the positive predictive value (PPV) was 100%. The median maximal standardized uptake value (SUVmax) in the primary tumor was 10.5, with a distribution of median SUVmax for TC and AC to be 7.65 (range 0.7 to 7.65) and 16.25 (range 1.9 to 110.1), respectively. Krenning score was available for 26 patients with a median Krenning score of 3. The most common Krenning score was 4 in 35% of the patients.
N=44
Surgical status Primary positive
Surgical status Primary negative
DOTATATE positive
40
0
DOTATATE negative
4
0
Pathological nodal status was N0, N1, N2 in 32(73%), 8(18%) and 4(9%) patients respectively. The intrapulmonary and interlobar nodal involvement (N1) has proximity with the primary lung mass and was considered negative on Ga-68 DOTATATE PET. Out of 4 patients with involvement of subaortic and/or subcarinal nodes (N2), Ga-68 DOTATATE PET was positive in 1 patient. The sensitivity and specificity of Ga-68 DOTATATE PET in metastatic N2 nodal involvement were 25% and 95%, respectively. PPV was 33%, and the negative predictive value was 93%. The median SUVmax of the primary tumor for patients with N0 disease was 9.35 (range 1.4 to 110.1) and with N1 or above disease was 17.3 (range 0.7 to 65.2).
N=44
Surgical status node positive
Surgical status node negative
DOTATATE positive
1
2
DOTATATE negative
3
38
Conclusions: Our results demonstrate high sensitivity and PPV of Ga-68 DOTATATE PET in detecting primary pulmonary neuroendocrine tumors (91% and 100 %, respectively). The median value of SUVmax of atypical carcinoids (16.25) is more than twice the value of typical carcinoids (7.65). Ga-68 DOTATATE has low sensitivity (25%) but high specificity (95%) in detecting true nodal metastasis.
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