Abstract 129P
Background
To verify the value of ctDNA and CTC as biomarkers for tumor response in the neoadjuvant chemotherapy (nCRT) treatment of locally advance gastric adenocarcinoma.
Methods
A total of 50 patients were enrolled. 20ml of plasma were collected at 3 points: before nCRT; after 2 cycles of nCRT; and after surgery. Firefly ctDNA NGS assays were used to track ctDNA mutations previously. Using patient-specific mutation derived from exome sequencing of tumor tissues samples. Tumor response data by CT were also collected. CTCs in 7ml peripheral blood were separated by a negative enrichment method and identified by FISH using two frequently proliferation chromosome probes, CEP8 and CEP17. Meanwhile, the HER2 expression in CTCs was determined by FISH and immunofluorescence. CEP8+ and/or CEP17+, DAPI+, CD45- cell were justified as CTCs, HER2 FISH+ or HER2 IF+, DAPI+, CD45- cells were justified as HER2 positive CTCs.
Results
A total of 10-20 somatic SNV or indel mutation were successfully identified for each patient. In comparison to basal line value of pre-chemotherapy blood, the ctDNA loading were decreased in post-chemotherapy specimens of 8 patients with TRG1 by histopathological grading or partial and complete response by CT scan. However, the amount of ctDNA in 25 patients diagnosed as TRG 2 or 3 showed minor changes during the neoadjuvant therapy. After surgery, 32 patients showed undetectable ctDNA in blood while 3 patients showed residual trace ctDNA. 22 patients have integral FISH data (CTCs before, after nCRT and after surgery range from 0-29, average: 4.9, 2.7 and 4.0, positive rate: 82%,73% and 73%), and 12 have integral HER2 data. The dynamic variations were coincidence to the clinical evaluation. For HER2, we found three positive model in CTCs, single FISH or IF positive or double positive. Double positive HER2-CTCs are found in some patients. By negative enrichment and FISH, CTCs can be detected at a low cutoff of 2 cells in 73%∼82% patients.
Conclusions
The ctDNA and CTC alteration during neoadjuvant therapy is consistent with conventional histopathological grading and radiological response assessment.
Clinical trial identification
NCT03425058.
Editorial acknowledgement
Legal entity responsible for the study
The author.
Funding
Has not received any funding.
Disclosure
The author has declared no conflicts of interest.
Resources from the same session
340TiP - A multicenter, randomized, controlled, phase II trial exploring adjuvant combined therapy of apatinib and SHR-1210 (anti-PD-1), in patients with hepatocellular carcinoma at high risk of recurrence after radical resection
Presenter: Shida Yan
Session: Poster display session
Resources:
Abstract
347P - Relationship between modified surgical margin and prognosis of cutaneous squamous cell carcinoma
Presenter: Yukiko Teramoto
Session: Poster display session
Resources:
Abstract
348P - Malignant melanoma: A study of clinical profiles and treatment outcomes in Indian patients
Presenter: Sorun Shishak
Session: Poster display session
Resources:
Abstract
349P - Flavonoids from ethanol extracts of euphorbia hirta inhibit melanoma growth and metastatic potential
Presenter: Shubhra Mishra
Session: Poster display session
Resources:
Abstract
350P - Low-dose cisplatin and 5-fluorouracil combined concurrent chemoradiotherapy for unresectable cutaneous squamous cell carcinoma: Analysis of 23 cases
Presenter: Azusa Hiura
Session: Poster display session
Resources:
Abstract
353P - A prediction model for the intents regarding life-sustaining treatment decisions in patients with terminal cancer
Presenter: Yoonsun Kim
Session: Poster display session
Resources:
Abstract
354P - Predictive factors and survival outcomes with stereotactic body radiation therapy in treatment of oligometastases in colorectal cancer
Presenter: Vibhay Pareek
Session: Poster display session
Resources:
Abstract
355P - Cost analysis and overview of single versus multiple fraction palliative radiotherapy for painful bone metastasis
Presenter: Vinodhkumar Selvaraj
Session: Poster display session
Resources:
Abstract
356P - Observational study on role of crude cannabis in pain control and quality of life in terminally ill cancer patients: An Indian perspective
Presenter: Vidyasagar Dusi
Session: Poster display session
Resources:
Abstract
357P - Application of multi-modal approach to palliation in end of life head and neck cancer pain
Presenter: Srujana Joga
Session: Poster display session
Resources:
Abstract