Somatostatin receptor expression in small cell lung cancer as a prognostic marker and a target for peptide receptor radionuclide therapy
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Constantin Lapa1, Heribert Hänscheid1, Vanessa Wild2, Theo Pelzer3, Andreas Schirbel1, Rudolf A. Werner1, Sabine Droll1, Ken Herrmann1, Andreas K. Buck1, Katharina Lückerath1
1Department of Nuclear Medicine, University Hospital Würzburg, 97080 Würzburg, Germany
2Institute for Pathology, University of Würzburg, 97080 Würzburg, Germany
3Department of Internal Medicine, University Hospital Würzburg, 97080 Würzburg, Germany
Constantin Lapa, e-mail: [email protected]
Keywords: small cell lung cancer, molecular imaging, somatostatin receptor, positron emission tomography, PET
Received: October 12, 2015 Accepted: February 16, 2016 Published: February 25, 2016
Despite initial responsiveness to both chemotherapy and radiotherapy, small cell lung cancer (SCLC) commonly relapses within months. Although neuroendocrine characteristics may be difficult to demonstrate in individual cases, a relevant expression of somatostatin receptors (SSTR) on the cell surface has been described. We aimed to evaluate the prognostic value of SSTR-expression in advanced SCLC. We further examined pre-requisites for successful peptide receptor radionuclide therapy (PRRT).
21 patients with extensive stage SCLC were enrolled. All patients underwent positron emission tomography/computed tomography (PET/CT) with 68Ga-DOTATATE to select patients for SSTR-directed therapy. PET scans were visually and semi-quantitatively assessed and compared to SSTR2a and SSTR5 expression in biopsy samples. Peak standardized uptake values (SUVpeak) of tumors as well as tumor-to-liver ratios were correlated to progression-free (PFS) and overall survival (OS).
In 4/21 patients all SCLC lesions were PET-positive. 6/21 subjects were rated “intermediate” with the majority of lesions positive, the remaining 11/21 patients were PET-negative. PET-positivity correlated well with histologic SSTR2a, but not with SSTR5 expression. Neither PET-positivity nor SUVpeak were predictors of PFS or OS. In 4 patients with intensive SSTR2a-receptor expression, PRRT was performed with one partial response and one stable disease, respectively.
SSTR-expression as detected by 68Ga-DOTATATE-PET and/or histology is not predictive of PFS or OS in patients with advanced SCLC. However, in patients exhibiting sufficient tracer uptake, PRRT might be a treatment option given its low toxicity and the absence of effective alternatives.
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