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Poster display session: Breast cancer - early stage, locally advanced & metastatic, CNS tumours, Developmental therapeutics, Genitourinary tumours - prostate & non-prostate, Palliative care, Psycho-oncology, Public health policy, Sarcoma, Supportive care

5881 - CTC-based biomarkers & PSMA-targeted imaging in patients with metastatic castrate-resistant prostate cancer (mCRPC)

Date

22 Oct 2018

Session

Poster display session: Breast cancer - early stage, locally advanced & metastatic, CNS tumours, Developmental therapeutics, Genitourinary tumours - prostate & non-prostate, Palliative care, Psycho-oncology, Public health policy, Sarcoma, Supportive care

Topics

Translational Research

Tumour Site

Prostate Cancer

Presenters

Michael Morris

Citation

Annals of Oncology (2018) 29 (suppl_8): viii271-viii302. 10.1093/annonc/mdy284

Authors

M.J. Morris1, N.J. Vogelzang2, O. Sartor3, A. Armour4, R. Messmann5, M. Groaning5, A. Robarts6, A.W. Tolcher7, M. Gordon8, H.M. Babiker9, P. Kuo9, M. Kearney10, A. Jendrisak10, Y. Wang11, M. Landers12, D.P. Petrylak13

Author affiliations

  • 1 Memorial Sloan-kettering Cancer Center, Memorial Sloan-Kettering Cancer Center, 10065 - New York/US
  • 2 Us Oncology Research C/o Comprehensive Cancer Crts Of Nv, US Oncology Research c/o Comprehensive Cancer Crts of NV, 89169 - Las Vegas/US
  • 3 Tulane Cancer Center, Tulane Medical School, New Orleans/US
  • 4 Endocyte, 46268 - Indianapolis/US
  • 5 Medical Affairs, Endocyte, 47906 - West Lafayette/US
  • 6 Gu, Memorial Sloan Kettering Cancer Center, New York/US
  • 7 Clinical research, NEXT OncologyTM, San Antonio/US
  • 8 Medical Oncology, HonorHealth Virginia G Piper Cancer Care Network, Scottsdale/US
  • 9 Cancer Center, University of Arizona Cancer Center, 85724-5024 - Tucson/US
  • 10 Clinical Operations, Epic Sciences, San Diego/US
  • 11 Translational Research, Epic Sciences, San Diego/US
  • 12 Translational Research, Epic Sciences, 92121 - San Diego/US
  • 13 Medical Oncology, Yale University School of Medicine Medical Oncology, 06520-8032 - New Haven/US
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Resources

Abstract 5881

Background

Prostate-specific membrane antigen (PSMA) is highly expressed in prostate cancers, making it an imaging & therapeutic target of interest. The utility of the PSMA-targeted imaging agent 99mTc-EC0652 is being evaluated, along with biomarker analysis of circulating tumor cells (CTCs), in pts with mCRPC in a completed PSMA-targeted chemotherapeutic study. We now report the PSMA heterogeneity via CTC vs. imaging in the pt population treated to date.

Methods

A total of 51 pts evaluated at the time of the data cut had baseline CT & bone scans performed in addition to a 99mTc-EC0652 SPECT/CT as a measure of imaging-based PSMA expression. 41 of 51 pts provided pre-treatment blood samples evaluable for CTC biomarker analysis, which included PSMA expression & predicted genomic instability status (pGI). Images collected from pts were analyzed for both their PSMA+ status as well as sensitivity relative to conventional imaging.

Results

41 of 51 pts (80.4%) had detectable CTCs in their samples prior to therapy while 32 of 38 (84.2%) of the analyzed paired on-therapy samples had CTCs after treatment. At baseline PSMA+ CTCs were found in 19 of 51 (37.2%) pts and overall was expressed on 33% (IQR 11.3% - 40.1%) of CTCs within each pt sample. 15 of 17 (88%) PSMA+ pt samples were also pGI+. 31 of the 51 pts (60.7%) of the pts had bone scan (BS) data available to analyze. 27 of the 51 pts had CT scan data available to analyze for nodal lesions. Concordance between Conventional Imaging & 99mTc-EC0652.Table: 842P

99mTc- EC0652+99mTc- EC0652-BS+BS-CT+CT -
Bone Lesion (770)770 (100%)0587 (76.2%)183 (23.8%)N/AN/A
Nodes >1.5cm (54)48 (88.9%)6 (11.1%)N/AN/A54N/A
Nodes <1.5cm (69)69N/AN/AN/AN/AN/A

Conclusions

In this cohort, most pts had CTCs for assessment. The majority of pts with CTCs had PSMA-CTCs. The pts CTCs expressing PSMA accounted for a small percentage of the total CTCs observed. These PSMA+ CTCs had high pGI. Pts with CTCs had PSMA imagable disease, especially in bone. The discordance between CTCs & imaging illustrate the disease heterogeneity in regards to PSMA expression. These data should be considered in designing future PSMA-directed regimens.

Clinical trial identification

NCT02202447.

Legal entity responsible for the study

Endocyte Inc.

Funding

Endocyte, Inc.

Editorial Acknowledgement

Disclosure

M.J. Morris, O. Sartor: Consultant: Endocyte. A. Armour, R. Messmann, M. Groaning: Employee: Endocyte. All other authors have declared no conflicts of interest.

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