212P - Correlation of 68Ga-SSO120 PET with SSTR2 expression and prognostic value in patients with small cell lung cancer

Background

Positron Emission Tomography (PET) imaging of the somatostatin receptor 2 (SSTR2)-antagonist satoreotide trizoxetan (SSO120, previously OPS202) is a novel technique for accurate staging of patients with small cell lung cancer (SCLC). Here, we evaluate the prognostic value of ⁶⁸Ga-SSO120 PET at initial staging of patients with SCLC and correlate uptake in PET imaging with SSTR2 expression in immunohistochemistry (IHC).

Methods

We retrospectively included patients who underwent ⁶⁸Ga-SSO120 PET/CT during initial diagnostic workup of SCLC. PET-positive tumor lesions were manually segmented and SUV_max/SUV_peak values were estimated. The whole-body SSTR2-expressing tumor volume (SSTR-TV) was calculated from all lesions per patient. For patients with available tumor biopsies, SSTR2 expression was assessed by IHC on a 4-level scale (0: negative, 1: 1-30%, 2: 30-70%, 3: ≥70%), which was correlated with SUV_max/SUV_peak in a lesion-based analysis. The association of SSTR-TV with overall survival (OS) was analysed by univariate Cox regression.

Results

We included 43 patients (22 female/21 male), 15 with limited and 28 with extensive disease according to VALG classification. Mean administered activity was 142 MBq and mean uptake time 63 min. For 34 patients, pathological specimens were available. Lesion SUV_max/SUV_peak significantly correlated with histopathological SSTR2-expression (Spearman’s rho 0.73/0.70, p<0.001). Patients with a SSTR2-TV ≥130 mL (13 extensive, 2 limited disease, cut-off identified on data for best separation) showed a significantly shorter OS than patients with lower SSTR2-TV (15 extensive, 13 limited disease) (median OS: 10.8 vs. 16.1 mos; HR: 0.35, 95%-CI: 0.12-0.99, p=0.038).

Conclusions

In patients with SCLC, tumor uptake in ⁶⁸Ga-SSO120 PET correlates with histopathological SSTR2-expression and SSTR2-TV was associated with poorer OS. Investigation of a larger cohort is warranted to analyse other OS determinants (e.g., VALG and type of distant metastases) and to identify candidates for SSTR2-directed radionuclide therapy using ¹⁷⁷Lu-SSO110.

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

D.M. Kersting: Financial Interests, Personal, Research Grant: Pfizer. M. Wiesweg: Financial Interests, Personal, Invited Speaker: Amgen, Roche, Takeda, GSK, AstraZeneca; Financial Interests, Personal, Expert Testimony: GSK; Financial Interests, Personal, Advisory Board: Novartis, Pfizer, Roche, Janssen, Daiichi Sankyo; Financial Interests, Institutional, Invited Speaker: Takeda; Financial Interests, Institutional, Funding: Bristol Myers Squibb. L. Umutlu: Financial Interests, Personal, Advisory Board: Bayer, Siemens. W. Fendler: Financial Interests, Personal, Research Grant: SOFIE biosciences; Financial Interests, Personal, Invited Speaker: Janssen, Novartis, Telix; Financial Interests, Personal, Advisory Role: Calyx, Bayer; Financial Interests, Personal, Other: Parexel. K. Herrmann: Financial Interests, Personal, Advisory Board: Bayer, Adacap/Novartis, Curium, Boston Scientific, GE Healthcare, AstraZeneca; Financial Interests, Personal, Invited Speaker: Sirtex, Siemens Healthineers, Monrol; Financial Interests, Personal, Other, Consultant: Amgen; Financial Interests, Personal, Other, DMSB: ymabs; Financial Interests, Personal, Advisory Board, Scientific Advisor: AdvanceCell; Financial Interests, Personal, Advisory Board, Advisor, Consultant: Janssen; Financial Interests, Personal, Advisory Board, Consultant: Eco1R, Fusion Pharmaceuticals; Financial Interests, Personal, Expert Testimony, Consultant: Genentech; Financial Interests, Personal, Member of Board of Directors: Sofie Biosciences, Pharma 15; Financial Interests, Personal, Ownership Interest: Sofie Biosciences; Financial Interests, Personal, Stocks/Shares: Aktis Oncology, AdvanCell, Convergent Therapeutics; Non-Financial Interests, Personal, Leadership Role, Chair Oncology&Theragnostics Committee: EANM. M. Schuler: Financial Interests, Personal, Invited Speaker: Amgen, Boehringer Ingelheim, Bristol Myers Squibb, Janssen, Novartis, Roche; Financial Interests, Personal, Advisory Board: Amgen, AstraZeneca, Boehringer Ingelheim, Bristol Myers Squibb, GSK, Janssen, Merck Serono, Novartis, Roche, Sanofi, Takeda; Financial Interests, Institutional, Research Grant: Bristol Myers Squibb, AstraZeneca; Non-Financial Interests, Personal, Principal Investigator, Member, Study Steering Board: Janssen; Non-Financial Interests, Personal, Principal Investigator, Member, Study Steering Committee: Amgen. All other authors have declared no conflicts of interest.