Liquid biopsy- A pivotal test to help navigate clinical decisions at a precision center in India!

Abstract

Liquid biopsy, specifically circulating tumor DNA (ctDNA) analysis, has emerged as a transformative tool in precision oncology, providing real-time, minimally invasive characterizations of the tumor and tumor dynamics. While tissue biopsy is a critical tool for baseline diagnosis of malignancy, it is often limited by sampling constraints and an inability to capture tumor heterogeneity. In this study, we explored the clinical utility of serial ctDNA testing in guiding therapeutic decisions across a cohort of 30 patients with diverse solid tumors. Our real-world analysis demonstrates that ctDNA profiling meaningfully influenced treatment escalation, de-escalation, disease monitoring, and early relapse prediction. Cases where ctDNA positivity indicated minimal residual disease prompted timely escalation of therapy, while ctDNA clearance allowed safe treatment de-intensification, minimizing toxicity without compromising outcomes. Longitudinal ctDNA monitoring provided a dynamic, non-invasive method for assessing treatment response and detecting recurrence months before radiological progression. Our study highlights the potential of integrating liquid biopsy into routine clinical practice to enable dynamic treatment monitoring, early detection of therapeutic resistance, and more informed, personalized decision-making across various cancer types.

1. Introduction

Precision oncology has redefined cancer care enabling a universal strategy to individualize disease management. In this evolving landscape, liquid biopsies have played a crucial role in identifying actionable [1] targets, monitoring treatment response, and detecting emerging resistance mechanisms (see Table 1).

Table 1.

Overview of patient’s tumor type, disease stage, timing of liquid biopsy testing, treatment modifications based on liquid biopsy results, and the corresponding imaging response. This table highlights the role of liquid biopsy in guiding treatment decisions and assessing therapeutic outcomes.

Sr.no	Cancer Type	Staging	MRD Timepoint	MRD Result	Graphical representation of MTM/ml	Correspondence Imaging response	Clinical Action	Outcomes
1	Urothelial Carcinoma	Stage IV	Post treatment	Negative		Partial metabolic response	Treatment De-escalation	Alive
2	Breast carcinoma	Stage II	Post treatment	Positive		Local Recurrence	Early Relapsed	Deceased
			1st Followup	Positive		Disease Progression
3	Colorectal Carcinoma	Stage IV	Post Treatment	Negative		Complete Response	Disease Monitoring	Alive
			1st Followup	Negative
4	GE Junction Carcinoma	Stage III	Post Treatment	Positive		Partial metabolic response	Early Relapsed	Alive
			1st Followup	Positive		Disease Progression
5	Colorectal carcinoma	Stage III	Post treatment	Negative		Partial metabolic response	Disease Monitoring	Alive
6	Uterine Sarcoma	Stage IB	Post Treatment	Negative		Complete response	Disease Monitoring	Alive
			1st Followup	Negative		Complete response
			2nd Followup	Negative		Complete response
7	Ampullary carcinoma	Stage II	Post treatment	Negative		Partial metabolic response	Disease Monitoring	Alive
8	Colorectal Carcinoma	Stage II	Post treatment	Negative		Complete response	Disease Monitoring	Alive
			1st Followup	Negative		Complete response
9	Cervix Carcinoma	Stage IB	Post treatment	Negative		Complete response	Disease Monitoring	Alive
10	Thyroid carcinoma	Stage IB	Post Treatment	Positive		Complete response	Disease Monitoring	Alive
11	High grade Retroperitoneal Sarcoma	Stage III	Post Treatment	Negative		No Imaging done	Disease Monitoring	Alive
12	Colon Adenocarcinoma	Stage III	Post Treatment	Negative		Good response to treatment	Treatment De-escalation	Alive
			1st Followup	Negative
			2nd Followup	Negative
13	Breast carcinoma	Stage II	Post Treatment	Negative		Complete response	Disease Monitoring	Alive
14	Lung Carcinoma	Stage IV	Post Treatment	Negative		Complete response	Early Relapsed	Alive
			1st Followup	Negative		Complete response
			2nd Followup	Positive		Progression
15	Breast carcinoma	Stage IIB	Post Treatment	Negative		Complete response	Disease Monitoring	Alive
16	Rectum Carcinoma	Stage II	Post Treatment	Negative		No imaging done	Treatment De-escalation	Alive
			1st Followup	Negative
17	Colon Adenocarcinoma	Stage III	Post Treatment	Negative		Complete response	Disease Monitoring	Alive
			1st Followup	Negative
18	Sigmoid carcinoma	Stage III	Post Treatment	Positive		Disease progression	Escalated treatment	Alive
19	Pancreas neuroendocrine Tumor	Stage IV	Post Treatment	Positive		Disease recurrence	Early Relapsed	Alive
20	Periampullary carcinoma	Stage II	Post Treatment	Negative		No imaging done	Disease Monitoring	Deceased
21	Colorectal carcinoma	Stage III	Post Treatment	Positive		Good response to treatment	Disease Monitoring	Alive
			1st Followup	Positive
22	Endometrial Carcinoma	Stage IA	Post Treatment	Negative		Good response to treatment	Disease Monitoring	Alive
			1st Followup	Negative
			2nd Followup	Negative
23	Lung Adenocarcinoma	Stage IIB	Post Treatment	Positive		Maintenance treatment	Disease Monitoring	Alive
			1st Followup	Negative
			2nd Followup	Negative
24	GE Junction	Stage IV	Post Treatment	Negative		Disease Progression	Early Relapsed	Deceased
			1st Followup	Positive
			2nd Followup	Positive
25	Ovarian Carcinoma	Stage IIIC	Post treatment	Negative		Disease Progression	Escalated treatment	Alive
			1st Followup	Negative
			2nd Followup	Positive
26	Cholangiocarcinoma	Stage IV	Post treatment	Positive		Disease progression	Escalated treatment	Alive
			1st Followup	Positive		Disease Progression
			2nd Followup	Positive		Stable disease
27	Ampullary Carcinoma	Stage III	Post Treatment	Negative		Stable disease	Treatment De-escalated	Alive
			1st Followup	Negative
			2nd Followup	Negative
28	Lung NSCLC	Stage IV	Post treatment	Negative		Complete response	Disease Monitoring	Alive
			1st Followup	Negative
			2nd Followup	Negative
29	Lung Adenocarcinoma	Stage III	Post treatment	Negative		Complete treatment	Disease Monitoring	Alive
			1st Followup	Negative
30	Breast Carcinoma	Stage II	Post treatment	Negative		Disease progression	Escalated treatment	Alive
			1st Followup	Negative
			2nd Followup	Positive

While solid tissue biopsy remains the cornerstone for initial diagnosis and genomic assessment, it is often limited by sampling constraints, procedural risks, and inability to reflect tumor heterogeneity. In contrast, liquid biopsies offer a minimally invasive method to assess real-time disease dynamics and allows identification of low-frequency and evolving mutations, often undetected by conventional tissue-based methods. Our recent study, demonstrated circulating tumor DNA (ctDNA) based profiling assay as a reliable alternative for management of lung cancer patients-a real-world data [2]. Here we attempt to explore how liquid biopsies performed at critical time points in a patient’s clinical journey, could help strategize clinical decision making and actively guide treatment escalation, de-escalation, or early relapse monitoring in routine oncology practice.

We present a series of real-world cases where longitudinal liquid biopsies help navigate treatment decisions [3]. Through this analysis, we aim to highlight the pragmatic value of integrating sequential genomic insights into standard cancer care, demonstrating its impact [4] on personalizing therapy, minimizing overtreatment, and detecting relapse before radiologic progression.

2. Case description

In a cohort of 30 cases treated at our precision center, representing a spectrum of solid tumor types and disease stages, studied retrospectively, ctDNA analysis was integrated into the clinical workflow to guide treatment decisions. Following initial diagnosis, all patients underwent standard-of-care therapy. Liquid biopsy testing was performed along with conventional imaging such as CT (Computed tomography Scan) scan and PET-CT (Positron Emission Tomography/Computed Tomography) at different time points, to help with clinical decisions in the precision oncology clinic. The liquid biopsy results exhibiting dynamic changes in concentration provided critical insights that influenced subsequent clinical decisions and management. Based on the nature of the decision informed by the liquid biopsy status, we stratified patients into four key categories of clinical impact: treatment escalation, treatment de-escalation, response monitoring, and early relapse prediction. Three tests were utilized – Signatera (Natera), Cancer track Analysis (Datar), Guardant Reveal (Guardant 360).

Treatment change or escalation: In a subset of patients, detection of ctDNA following initial therapy indicated residual disease, prompting escalation of treatment. For example, a patient with stage III gastroesophageal (GE) junction cancer exhibited a rise in ctDNA after completion of neoadjuvant therapy by surgery followed by adjuvant therapy, warranting early PET-CT scan for disease tracking, only to confirm progressive disease leading to escalation of therapy to 5-fluorouracil, irinotecan, and nivolumab as the next treatment. Similarly, in a case of stage III sigmoid colon cancer, ctDNA positivity following surgery guided the initiation of adjuvant chemotherapy. Another notable case involved a patient with stage IV pancreatic neuroendocrine tumor who had undergone treatment with sandostatin injections followed by surgery. High ctDNA levels at follow-up led to an escalation of therapy with peptide receptor radionuclide therapy (PRRT).

Treatment de-escalation: Treatment de-escalation was possible ctDNA negativity following initial treatment led to the de-escalation of therapy, reducing treatment-related toxicity without increasing the risk of recurrence. For instance, in a patient with metastatic urothelial carcinoma, ctDNA negativity alongside a complete radiological response supported the discontinuation of enfortumab which had given significant neuropathy to the patient. This allowed the patient to continue pembrolizumab maintenance with significantly reduced toxicities. Similarly, in an oligometastatic colorectal and rectal cancer case, ctDNA negativity supported a shift to no maintenance therapy due to low risk of relapse and concerns for toxicity. In another patient with periampullary carcinoma and significant comorbidities, ctDNA negativity supported the decision to withhold further therapy, avoiding additional toxicity.

Response monitoring: Longitudinal ctDNA testing plays a pivotal role in monitoring treatment response and guiding clinical management decisions over time. In several cases, ctDNA negativity following definitive therapy supported continued observation or maintenance therapy without escalation as discussed. Patients with colorectal, endometrial, uterine, breast, cervical, and lung cancers who showed complete radiological responses were maintained on either surveillance or minimal therapy, with ctDNA remaining undetectable across follow-up timepoints. In one patient with stage III colorectal cancer PET-CT positive for a para-aortic lymph node concerning for early relapse, ctDNA was utilized as a non-invasive alternative to lymph node biopsy, especially since this node was unreachable for CT guided biopsy and a laparoscopic evaluation was warded off when the ctDNA came back negative successively upon tracking. The patient was kept under close surveillance through longitudinal ctDNA monitoring, which consistently remained negative, allowing continued observation without the need for further intervention or systemic therapy. In patients with advanced endometrial cancer patient receiving immunotherapy, and breast cancer patient receiving hormonal therapy, ctDNA negativity was concordant with radiologic response and supported continuation of the current regimen. In another example, a patient with Epidermal growth factor receptor (EGFR) positive stage IIB lung adenocarcinoma, adjuvant treatment with carboplatin and pemetrexed yielded continued disease control, in addition, the undetectable ctDNA guided the continued maintenance therapy with Osimertinib. In another notable case of second primary in the form of stage III microsatellite instability high colorectal cancer, chemotherapy was avoided due to persistent sever neuropathy due to previous folinic acid, fluorouracil, and oxaliplatin (FOLFOX)/oxaliplatin exposure and the patient was treated with immunotherapy alone. High ctDNA levels during early pembrolizumab therapy gradually declined over subsequent cycles, correlating with PET-CT response and supporting single agent adjuvant immunotherapy with pembrolizumab. Across this cohort, ctDNA provided a non-invasive way to monitor disease in real time, guiding follow-up decisions.

Early Relapse Prediction: In certain cases, ctDNA positivity reflected early relapse before it was detectable by imaging, prompting timely therapeutic intervention. Both tumor informed and tumor agnostic methods of minimal residual disease monitoring were utilized in these real-world cases. For example, in a patient with stage II breast cancer, rising ctDNA levels indicated local recurrence even prior to PET-CT confirmation. Another patient who was in complete pathological remission following multiple lines of therapy, showed ctDNA reappearance, which was subsequently validated by imaging and led to re-initiation of treatment. Similarly, in a case of GE junction carcinoma under maintenance therapy, ctDNA positivity during follow-up confirmed progression, guiding a switch to irinotecan.

3. Discussion

Liquid biopsy has transitioned from proof of concept to a highly sophisticated clinical tool to guide decision-making either as a complimentary test, or especially when getting a tissue biopsy is difficult. Liquid biopsy is being widely utilized today for minimal residual disease tracking and adjuvant and maintenance treatment strategy development. By enabling serial, minimally invasive sampling of ctDNA, we can capture spatial and temporal tumour heterogeneity at a greater extent compared to tissue biopsy.

In our series of 30 patients, representing nine different solid tumor histologies, from a single precision center practice in India, the integration of ctDNA profiling with conventional imaging, transformed the management of their disease in multi-dimensional ways. It prompted treatment escalation in cases where minimal residual disease (MRD) persisted, allowed for treatment de-escalation when ctDNA cleared, provided dynamic pathway therapy strategy, and predicted relapse information several months prior to radiographic progression.

Our collated data highlights various multitudes of liquid biopsy utilization for management of treatment escalation cases where ctDNA driven MRD assessment led to treatment escalation in these patients. This approach is now supported by evidence from the DYNAMIC trial which showed that adjuvant chemotherapy directed only to ctDNA-positive stage II colon cancer patients preserved recurrence-free survival in these patients, while sparing the ctDNA-negative patients unnecessary toxicity from treatment that was not required [5]. Additionally, the large GALAXY observational study in stages II–III colorectal cancers also reported a 12-fold higher relapse risk when ctDNA remained detectable post-operatively [6].

In another study the escalation of treatment showed benefit in invasive urothelial carcinoma, where ctDNA-positive patients derived an overall-survival advantage from adjuvant atezolizumab [7]. For advanced neuroendocrine cancers, the emerging studies suggest that ctDNA could rationalize early use of peptide receptor radionuclide therapy and even extend into rarer entities such as pancreatic neuroendocrine tumors [8]. Many prospective clinical trials are now designed to intervene at molecular relapse rather than waiting for radiographic progression. c-TRAK TN triggered pembrolizumab in ctDNA-positive Triple Negative Breast Cancer survivors, while MERMAID-1 trial is testing adjuvant durvalumab exclusively in ctDNA-positive non-small cell lung carcinoma (NSCLC) [9]. Both strategies aim to treat when tumour burden is at the lowest. Chaudhuri et al. (2017) showed that ctDNA detection after definitive therapy predicted recurrence well before radiological evidence and offered a window for timely treatment escalation [10]. In lymphoma, Kurtz et al., 2018 established that ctDNA clearance after first-line treatment in diffuse large B-cell lymphoma was correlated with favorable outcomes and there was potential for safe therapy de-escalation, while persistent ctDNA marked patients at high risk for relapse and thus calling for escalation of therapy [11]. Conversely, four patients whose ctDNA cleared after systemic therapy safely underwent de-intensification, supporting data that ctDNA negativity confers a more than seven-fold reduction in recurrence risk and supports treatment de-escalation [12].

In our case study, majority of our cohort were followed longitudinally with ctDNA; mirroring prospective monitoring data from studies such as BESPOKE-CRC [13] and TRACE Rx NSCLC, where ctDNA dynamics anticipated radiographic progression by weeks to months [14]. Finally, rising ctDNA predicted relapse at a median of 3–4 months before PET-CT in five patients, consistent with early-stage lung cancer study data that residual ctDNA predicts relapse roughly five months ahead of imaging [15]. Taken together these observations align closely with contemporary clinical trial evidence, reinforcing ctDNA’s value as a practical, minimally invasive biomarker strategy that can help inform an early treatment strategy modification and predictor of treatment response or lack thereof.

Liquid biopsy represents a paradigm shift, transforming oncology from reactive to proactive management. It facilitates earlier intervention, reduces dependence on stand-alone invasive procedures, and aligns with precision oncology's goal of tailoring therapies based on evolving tumor biology rather than static initial diagnoses. Supplementary Table 1 summarizes the multimodal integration of ctDNA in decision making. Our findings reinforce the utility of ctDNA in navigating decisions in multimodal treatment modulation-the core of precision oncology (Fig. 1).

Fig. 1.

ctDNA-guided treatment decisions across the cancer care continuum. The figure depicts ctDNA dynamics over time in response to different treatment strategies such as treatment monitoring (yellow), therapy de-escalation (pink), escalation (blue), and relapse prediction (teal). Thresholds for recurrence, minimal residual disease (MRD) and complete response are marked to demonstrate the ctDNA-based decision making.

Funding sources and disclosure of conflicts of interest

Dr Aditya Shreenivas.

Dr. Shreenivas serves on the advisory board of Merus, Taiho, and Elli Lilly. He also serves as a steering committee member of a Bayer-sponsored study.

The other authors declare no conflicts of interest.

No funding was availed.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Appendix A. Supplementary data

The following is the Supplementary data to this article: