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e17540 Background: Ovarian clear cell carcinoma (OCCC) is a rare subtype with distinct histologic and molecular features. The prognosis of advanced/recurrent OCCC treated with standard of care surgery and platinum-based chemotherapy remains poor due to inherent chemoresistance. Therefore, there is an urgent need to identify novel biological insights and personalized treatment approaches to improve outcomes. Methods: Participants were referred to the SMMART Program at the OHSU Knight Cancer Institute. Archival or fresh tissue was obtained from metastatic sites and processed through a multiomics platform that included immunohistochemistry (Ki67, HER2, CD4, CD8, PD-L1), fluorescent in-situ hybridization, targeted next-generation sequencing panel (225 genes), whole transcriptomic sequencing, chromosomal microarray, and multiplexed analysis of 67 key cancer proteins and phosphoproteins on the Nanostring GeoMx Digital Spatial Profiler. Results: 5 participants were enrolled with an average age of 62 years (range 52-72). Therapeutically relevant findings included detectable HER2 expression by IHC (2+, N=2; 3+, N=2), HER2 amplification by FISH (N=2), and high HER2 and phospho-HER2 protein expression compared to a breast cancer cohort (phospho-HER2 supports active HER2 signaling in the tumor cells). Additional findings include TMB 1% (N=3), low homologous recombination deficiency score (N=4), chromosomal losses including ATM, SMAD4, RB1, and TP53, and single nucleotide variations in ARID1A (N=4). Two participants with HER2 expression were treated with off-label trastuzumab deruxtecan for 6 or 7 cycles yielding significant clinical benefit. Participant A (HER2 = 3+, FISH negative) had an exceptional response while Participant B (HER2 = 2+, FISH amplified) had stable disease. The toxicity profile was consistent with literature. Conclusions: Our OCCC cohort revealed elevated HER2 expression with or without genomic amplification in 4/5 cases. Two participants experienced clinical benefit when treated with trastuzumab deruxtecan, supporting further exploration of HER2 antibody drug conjugates in this aggressive disease. More study is needed to determine the frequency of HER2 overexpression and amplification in OCCC, the importance of HER2 on OCCC pathophysiology, and the therapeutic benefit of targeting HER2 in this population.
Kong et al. (Sat,) studied this question.