Authors

Khandare J, Ghadyalpatil N, Raja T, Velukuru S, Jadhav V, Satape R, Shinde S, Ashturkar A, Dattatreya P, Vasudevan A

Affiliations:

Actorius Innovations and Research, Pune, Maharashtra, India

Apollo Cancer Institute, Hyderabad, Telangana, India

Apollo Cancer Centre, Chennai, Tamil Nadu, India

Aster CMI Hospital, Bengaluru, Karnataka, India

Renova Soumya Cancer Center, Hyderabad, Telangana, India

Introduction

Gastric cancer is associated with a high mortality rate, primarily due to late-stage diagnosis, which reduces the effectiveness of treatments such as surgery and results in poor five-year survival outcomes. The rate of metastasis in early-stage gastric cancer (EGC) varies, with reported lymph node metastasis rates ranging from approximately 10% to over 23%, depending on factors such as tumor invasion depth. Although most EGC cases do not initially present with distant metastasis, a substantial proportion of patients are diagnosed at advanced, metastatic stages. In this study, we evaluated gastrointestinal cancer patients for minimal cellular residual disease using circulating tumor cells (CTCs) expressing PD-L1 and the presence of CTC clusters.

Methods

A total of 58 gastric cancer samples were retrospectively analyzed. CTCs were isolated using the CDSCO India–approved OncoDiscover® CTC Test, which employs immunomagnetic enrichment with anti-EpCAM antibodies. CTCs were identified through immunocytochemical staining as CK18⁺, DAPI⁺, and CD45⁻ cells. Fluorescence imaging was performed using a Zeiss Axio Observer 7 microscope, and signal intensities were quantified. PD-L1 expression on CTCs was also evaluated. Statistical analyses summarized total CTC counts, PD-L1–positive CTCs, and the presence of CTC clusters.

Results

Among the 58 gastric cancer patient samples analyzed, CTCs were detected in 62.1% (36/58) of cases, while 37.9% (22/58) were CTC-negative. Most samples (93.1%) were collected at baseline, and 6.9% at follow-up. Among CTC-positive cases, PD-L1 expression was observed in 51.7%, while 8.7% were PD-L1-negative. CTC clusters were identified in 83.3% (30/36) of CTC-positive patients. Regarding CTC count distribution, 31.0% of patients had one CTC, 18.9% had two, and 12.07% had three CTCs. For PD-L1–positive CTCs, 14.3% of patients had zero detectable CTCs, 51.4% had one, 25.7% had two, and 8.6% had three CTCs. The mean CTC count across all samples was 1.0, the mean number of PD-L1–positive CTCs was 0.8, and the mean cluster count was 0.1. Demographic analysis showed male predominance (61.1%), with the most represented age group being 61–70 years (29.6%), followed by 41–50 years (22.2%) and 51–60 years (20.4%).

Conclusions

CTCs, particularly those expressing PD-L1 and forming clusters, are prevalent in gastric cancer patients and may serve as valuable biomarkers for diagnosis and prognosis. Their detection may help assess minimal cellular residual disease (MCRD) and identify patients at risk of recurrence.