Postoperative ctDNA in Pancreatic & Oral Cancer, Desmoid Tumor Therapy

Prognostic value of postoperative circulating tumor DNA and tumor markers in resected pancreatic adenocarcinoma (PAAD): an interim analysis of a prospective observational study

Poster Number: 482

This is a prospective, observational cohort study aimed at evaluating the potential of postoperative ctDNA-based minimal residual disease (MRD) as an early predictor of disease recurrence in pancreatic cancer. As of November 27, 2024, a total of 133 KRAS-mutated stage I-III PAAD resected patients were enrolled. Tumor tissue samples collected during surgery were subjected to NGS testing of 769 genes, and plasma samples were collected at multiple time points: 4-8 weeks post-surgery (before adjuvant therapy), and at 12, 24, 36, 48 weeks post-surgery, as well as 2 weeks after adjuvant therapy. After excluding patients lost to follow-up or with less than 6 months follow-up, 112 patients were included in the interim analysis.

Results showed that MRD positivity at the landmark time point (4-8 weeks post-surgery) was a significant predictor of disease recurrence (HR=2.39), and combining MRD with CA19-9 improved prognostic accuracy (HR=2.7). Longitudinal MRD positivity was associated with worse disease-free survival (DFS) and overall survival (OS).

Notably, patients who converted from landmark MRD positive to post-treatment negative (MRD clearance) showed significantly improved DFS, with no deaths reported. These findings suggest that integrating key timepoint and dynamic MRD assessments along with tumor markers is of important clinical value for risk stratification and prognosis evaluation in PAAD patients, potentially guiding personalized treatment and improving outcomes.

Prospective validation of dynamic circulating tumor DNA (ctDNA)-based MRD for predicting progression-free survival and treatment benefit in oral cancer

Abstract Number: e18090

This real-world study enrolled HPV-negative oral squamous cell carcinoma patients diagnosed by biopsy between 2021 and 2023. A total of 46 patients were analyzed with a median follow-up of 297 days. Among them, 11 patients (24%) experienced disease recurrence. In 44 patients with evaluable postoperative MRD, 10 (23%) were MRD positive. MRD positivity significantly predicted worse progression-free survival (PFS) (HR=6.07). Multivariate analysis demonstrated MRD positivity as an independent predictor of PFS (HR=8.50).

Notably, among postoperative MRD-positive patients, those receiving adjuvant therapy showed significantly improved PFS compared to those without adjuvant therapy (HR=5.68); while adjuvant therapy had no significant effect in MRD-negative patients. The longitudinal ctDNA positivity rate was 28%, and the negative predictive value increased to 91%. Postoperative ctDNA-based MRD shows potential in identifying disease recurrence and distinguishing patients likely to benefit from adjuvant therapy. Continuous MRD assessment during and after adjuvant therapy is crucial for disease monitoring and improving clinical outcomes in oral cancer patients.

Efficacy and molecular predictors of radiotherapy combined with bevacizumab on desmoid tumor (aggressive fibromatosis)

Abstract Number: e23535

This retrospective, biomarker-adaptive clinical study aimed to evaluate the efficacy and molecular predictors of radiotherapy combined with bevacizumab in treating desmoid tumors. The study included 160 pathologically confirmed desmoid tumor patients, of whom 8 patients treated with radiotherapy (median dose 51 Gy, range 45-65.5 Gy) combined with bevacizumab (2-5 cycles, 200-345 mg/cycle) were included in the final analysis cohort. The median patient age was 30 years (range 18-69), with tumors primarily located in the chest wall, head and neck, and thoracic cavity.

Treatment outcomes showed 3 patients (37.5%) achieved complete remission, 4 patients (50%) partial remission, and all patients maintained progression-free survival, with an average time to treatment failure (TTF) of 53.25 months (range 10-134 months). Quality of life scores were excellent (mean 90.6 ± 12.1). Molecular analysis revealed ATR gene mutations (involved in DNA repair) were detected only in patients with complete remission (3/3, 100%), and gene function enrichment analysis indicated the mutations were significantly associated with DNA repair and angiogenesis pathways.

The study indicates that radiotherapy combined with bevacizumab can achieve long-term control of desmoid tumors while maintaining good quality of life. ATR gene mutations may serve as key predictive markers of efficacy by influencing treatment sensitivity through regulation of DNA damage repair pathways, warranting further prospective studies to validate their clinical value.