More Removed Lymph Nodes Linked to Worse Outcomes After Immunotherapy in Colorectal Cancer

For decades, surgeons have operated on the assumption that when it comes to removing lymph nodes in cancer surgery, more is better. A thorough lymph node dissection has long been considered the gold standard, ensuring accurate staging and reducing the chance that malignant cells are left behind. But a new study is challenging that orthodoxy in a very specific and increasingly important context: colorectal cancer patients who receive immunotherapy before their operation. The research, published in BMC Cancer, suggests that patients who had more tumor-draining lymph nodes removed after neoadjuvant immune checkpoint inhibitor therapy experienced worse recurrence-free survival than those who had fewer nodes taken out, a finding that runs directly counter to conventional surgical wisdom and could reshape how surgeons think about the extent of dissection in the immunotherapy era.

The retrospective cohort study analyzed data from 195 colorectal cancer patients who underwent curative surgery following neoadjuvant immune checkpoint inhibitor therapy. The researchers, led by Bo Liu and Bo Li with corresponding authors Jinzhu Zhang, Xueqiang Jian and Zhanlun Liu, examined the relationship between lymph node yield, the total number of lymph nodes retrieved and examined by the pathologist after surgery, and postoperative recurrence. Their central finding was striking: patients with a lymph node yield of twenty or more nodes had significantly poorer recurrence-free survival than patients with lower yields. This association persisted across subgroup analyses stratified by pathological tumor stage, microsatellite status, the type of immune checkpoint inhibitor used, and the neoadjuvant treatment strategy, indicating that the signal was not confined to a narrow slice of the patient population.

To understand why this finding matters, it helps to consider the biology of tumor-draining lymph nodes. These are the lymph nodes that receive drainage from the tumor site, and they are far more than passive filters. They are active immunological hubs where dendritic cells present tumor antigens to naive T cells, where anti-tumor immune responses are primed, and where the immune system mounts its organized defense against cancer. Immune checkpoint inhibitors, drugs that unleash T cells by blocking inhibitory receptors such as PD-1, depend heavily on this lymph node machinery. In many cancers, the response to checkpoint blockade is initiated in the tumor-draining lymph nodes, where T cells are activated and then traffic to the tumor to do their work. Removing these nodes, therefore, might not be an immunologically neutral act.

The study’s single-cell analysis adds a fascinating layer to the story. The researchers performed single-cell RNA sequencing and T-cell receptor sequencing on tumor tissue, peripheral blood, and tumor-draining lymph node samples from colorectal cancer patients. This allowed them to track individual immune cells and, crucially, to identify which T cells in the tumor were clonally related to T cells in the lymph nodes, meaning they shared identical T-cell receptor sequences and therefore descended from the same activated precursor cells. What they found was that patients treated with immune checkpoint inhibitors exhibited a higher frequency of clonally shared CD8-positive effector memory T cells between the tumor-draining lymph nodes and the tumor tissue itself.

This clonal sharing is direct evidence of immunological connectivity between the lymph nodes and the tumor. It suggests that T cells activated in the tumor-draining lymph nodes, under the stimulus of checkpoint blockade, are physically migrating to the tumor and participating in the anti-cancer attack. In other words, the lymph nodes are not just staging grounds for the immune response; they are functioning as the factories that produce the tumor-fighting T cell army that immunotherapy mobilizes. When surgeons remove twenty or more of these nodes, they may be inadvertently dismantling a critical component of the patient’s own anti-tumor immune infrastructure at precisely the moment when immunotherapy has primed it for action.

The clinical implications are potentially significant, though the researchers are careful to note the limits of what their study can establish. As a retrospective cohort study, it demonstrates association rather than causation. It is possible that higher lymph node yield is a marker of more extensive disease or more aggressive surgical practice rather than a direct cause of recurrence. Patients with more nodes removed may have had more advanced disease that prompted wider dissections, or surgeons who remove more nodes may differ systematically in ways that affect outcomes. The authors themselves acknowledge that the mechanisms underlying the association remain unclear and warrant further investigation. Nevertheless, the consistency of the finding across multiple subgroup analyses, and its alignment with a plausible biological mechanism supported by the single-cell data, gives the result a credibility that demands attention.

The finding also sits within a broader and sometimes contentious debate in surgical oncology about the optimal extent of lymphadenectomy. In colorectal cancer, guidelines typically recommend examining at least twelve lymph nodes to ensure accurate staging, since understaging can lead to inadequate adjuvant treatment decisions. Lymph node yield has historically been used as a quality metric for both surgery and pathology, with higher yields generally interpreted as evidence of more thorough cancer care. The new study does not necessarily overturn that logic for patients who do not receive neoadjuvant immunotherapy, but it raises the provocative possibility that the optimal surgical strategy may differ depending on whether a patient’s immune system has been pharmacologically primed before the operation.

Neoadjuvant immunotherapy itself is a rapidly expanding approach in colorectal cancer, particularly for patients with mismatch repair-deficient or microsatellite instability-high tumors, which are exquisitely sensitive to checkpoint blockade. In these patients, preoperative immunotherapy can produce pathological complete responses, allowing some to avoid radical surgery altogether. As the use of neoadjuvant immunotherapy grows, questions about how to adapt standard surgical techniques become increasingly urgent. If tumor-draining lymph nodes are essential partners in the immunotherapy response, as this study’s single-cell data suggest, then the standard practice of extensive lymph node dissection may need to be re-evaluated in this specific patient population, balancing the staging benefits of node removal against the potential immunological cost.

The study also highlights the power of single-cell technologies to illuminate questions that traditional pathology cannot answer. By combining T-cell receptor sequencing across multiple tissue compartments, the researchers were able to visualize the traffic of immune cells between lymph nodes and tumors in a way that would have been impossible a decade ago. This kind of integrative analysis, linking clinical outcomes with high-resolution immune profiling, represents a model for how surgical oncology questions may be addressed in the future. Rather than asking simply how many nodes to remove, surgeons and oncologists may increasingly ask what immunological functions those nodes are performing and how to preserve them.

For now, the study’s authors urge caution rather than immediate changes to practice. The association between higher lymph node yield and poorer recurrence-free survival in immunotherapy-treated colorectal cancer patients is a hypothesis-generating finding, one that should prompt prospective studies designed to test whether more conservative lymph node management could safely improve outcomes. If those studies confirm the retrospective signal, the implications would extend beyond colorectal cancer to any malignancy treated with neoadjuvant immunotherapy and surgery. What is clear already is that the era of immunotherapy is forcing a re-examination of long-held surgical dogmas, and the humble lymph node, once viewed merely as a structure to be counted and cleared, is emerging as an active and potentially indispensable ally in the fight against cancer.

Subject of Research: The association between lymph node yield and recurrence-free survival in colorectal cancer patients treated with neoadjuvant immune checkpoint inhibitor therapy

Article Title: Higher lymph node yield is associated with increased postoperative recurrence in colorectal cancer treated with neoadjuvant immunotherapy: a retrospective cohort study

Article References: Liu, B., Li, B., Zhang, J., Jian, X., & Liu, Z. (2026). Higher lymph node yield is associated with increased postoperative recurrence in colorectal cancer treated with neoadjuvant immunotherapy: a retrospective cohort study. BMC Cancer. https://doi.org/10.1186/s12885-026-16966-4

Image Credits: AI Generated

DOI: 10.1186/s12885-026-16966-4

Keywords: colorectal cancer, immune checkpoint inhibitors, neoadjuvant immunotherapy, tumor-draining lymph nodes, lymph node yield, recurrence-free survival, single-cell RNA sequencing, T-cell receptor sequencing, CD8 T cells, lymphadenectomy, surgical oncology, tumor immunology