Author of

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  P26 - Mesothelioma, Thymoma and Other Thoracic Malignancies - Thymic Malignancies (ID 218)

  • Event: WCLC 2020
  • Type: Posters
  • Track: Mesothelioma, Thymoma and Other Thoracic Malignancies
  • Presentations: 1
  • Moderators:
  • Coordinates: 1/28/2021, 00:00 - 00:00, ePoster Hall

  • 35983

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    P26.04 - Correlation of Somatostatin Receptor 2 Expression, DOTATATE scan and Octreotide Treatment in Thymic Epithelial Tumors (ID 1650)

    00:00 - 00:00  |  Presenting Author(s): Anja C Roden
    • Abstract
    • Slides

    Introduction
    

    Somatostatin receptor 2 (SSTR2) has been shown to be overexpressed in a subset of neuroendocrine tumors and plays a role in imaging studies (68-Gallium DOTATATE PET/CT) and guiding therapy. Patients with tumors expressing SSTR2 might be successfully treated with somatostatin inhibitors such as Octreotide or 177-Lutetium DOTATATE. Although DOTATATE scans and Octreotide treatment are used in a subset of thymic epithelial tumors (TET), SSTR2 expression has not been systematically studied in these tumors. TET are considered malignant neoplasms and although many thymomas behave in an indolent manner, thymic carcinomas and some thymomas show aggressive behavior. Therefore, biomarkers that can predict outcome of targeted treatment are increasingly investigated. We studied expression of SSTR2 in TET and its correlation with DOTATATE results and treatment outcome.

    Methods
    

    An institutional database of TET (1941-present) was searched for thymic carcinomas and thymomas with available resection specimens. Cases were subtyped (2015 WHO classification) and staged (8^th AJCC/UICC staging). All cases were reviewed by a thoracic pathologist. A section was stained with anti-SSTR2 antibody (clone UMB1, Abcam) by immunohistochemistry. Percent tumor cells with membranous staining was recorded if present in >1% of tumor cells. Medical records were searched for DOTATATE scans and treatment. Reported results of DOTATATE scans were recorded. Data analysis was descriptive.

    Results
    

    Table 1: Summary of patients who underwent DOTATATE scan

    Patient	TET	pTNM Stage	SSTR2 expression (% tumor cells positive)	Kenning Score (or description) of DOTATATE scan	Treatment & Outcome
    1	Squamous cell carcinoma	T3N1M0	0	Increased uptake	Incomplete resection Adjuvant radiation Lost to follow up Died 4 years after resection of unknown cause
    2	Atypical carcinoid tumor	T3N1M0	10	No uptake	Complete resection Adjuvant radiation Metastases 15 months after resection Chemotherapy Died of disease 3.5 years after resection
    3	Atypical carcinoid tumor	T3N1M0	95	3	MEN1 syndrome Neoadjuvant and adjuvant radiation Complete resection Octreotide Metastasis 3.3 years after resection Tyrosine kinase inhibitor and chemotherapy Progressive disease Octreotide and chemotherapy followed by LU-DOTATATE Stable disease 9.3 years after resection Alive with disease
    4	Atypical carcinoid tumor	T3N1M1	0	1	Complete resection Adjuvant radiation Metastases 3.2 years after resection Alive with disease
    5	Atypical carcinoid tumor	T1N1M1	0	2	Complete resection Metastasis to breast 4 months after resection Chemotherapy, followed by resection Alive without disease 11 months after resection

    Sixty-five cases were identified with a median age of 59.4 years (range, 19.1-87.3) (29 males, 44.6%) included small cell carcinoma (N=1), squamous cell carcinomas (18), sarcomatoid carcinoma (1), atypical carcinoid tumors (4), undifferentiated carcinoma (1), adenocarcinomas (3), mucoepidermoid carcinomas (2), adenosquamous carcinoma (1), lymphoepithelioma-like carcinomas (2), and thymomas (32). SSTR2 expression was identified in 22 (of 65, 33.8%) TET including 1 (of 1, 100%) small cell carcinoma (2% of tumor cell staining), 13 (of 18, 72.2%) squamous cell carcinomas (median, 40% of tumor cell staining, range, 5-100), 2 (of 4, 50%) atypical carcinoid tumors (range, 10-95% staining), 1 (of 1, 100%) adenosquamous carcinoma (5% staining), 2 (of 2, 100%) lymphoepithlioma-like carcinomas (70% staining, both), 2 (of 32, 6.2%) thymomas (5% staining both). Of these cases, a DOTATATE or DOTATOC PET/CT at time of surgery was available in 5 cases which are detailed in table 1.

    Conclusion
    

    TET including lymphoepithelioma-like carcinomas and a subset of atypical carcinoid tumors and squamous cell carcinomas express SSTR2 in over 50% of tumor cells. In a subset of these tumors, DOTATATE PET scans reveal disease potentially treatable by targeting SSR2 with octreotide or 177-Lutetium DOTATATE treatment.

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