Correlation of tumor-naive methylation-based preoperative ctDNA testing with pathologic upstaging and occult metastasis in early-stage solid tumors.

1616 Background: The TNM staging system serves as the cornerstone for most solid tumor treatment strategies. However, preoperative evaluation of early-stage cancers is not always reliable, with a particular propensity to overlook occult lymph node metastasis (OLNM) or even distant metastases. In turn, incorrect staging may lead to suboptimal perioperative decisions, including inappropriate surgical strategies, unjustified neoadjuvant therapy, and inadequate lymph node dissection. This study evaluated whether preoperative circulating tumor DNA (ctDNA) detected by methylation-based assay is associated with pathologic upstaging and the presence of OLNM or distant metastasis across multiple types of solid tumor. Methods: This study analyzed preoperative blood samples from a validation cohort within a multi-cancer early detection (MCED) study, encompassing 16 high-burden cancer types in China. Lymphomas, liver cancer, and nasopharyngeal carcinoma were excluded, due to limited use of TNM staging and/or non-routine radical surgery. Patients who had received neoadjuvant therapy were also excluded. ctDNA was detected using a targeted methylation-based MCED assay. Associations between ctDNA positivity and discrepancies between clinical (cTNM) and pathologic (pTNM) staging-including upstaging due to OLNM or distant metastasis-were examined statistically. Results: A total of 681 cases of clinical stage I–II cancers were analyzed, including lung cancer (n=124), breast cancer (n=113), colorectal cancer (n=88), gastric cancer (n=79), pancreatic cancer (n=55), cervical cancer (n=54), ovarian cancer (n=36), prostate cancer (n=34), esophageal cancer (n=32), endometrial cancer (n=31), bladder cancer (n=17), renal cancer (n=17), and gallbladder cancer (n=1). Preoperative ctDNA was detectable in 46.8% (184/393) of stage I and 71.5% (206/288) of stage II patients. ctDNA-positive patients were more likely to undergo pathologic upstaging than ctDNA-negative patients (16.9% vs. 6.9%; p=0.0002). For patients with clinical N0 (cN0), OLNM (defined as preoperative cN0 with postoperative confirmation of pN1–3) was more common in ctDNA-positive patients（12.6% vs. 4.7%; p=0.0012）. Among clinically M0 patients, three were confirmed as pathologic M1, all ctDNA-positive. Conclusions: Methylation-based preoperative ctDNA testing correlates with pathologic upstaging and OLNM, and may also be associated with occult distant metastasis. This finding supports the potential of ctDNA testing to refine preoperative staging and inform perioperative decision-making. Further validation with an expanded sample size will be conducted in an additional blinded cohort to confirm these findings.