A recent study published in Cell Reports Medicine offers a troubling yet scientifically grounded answer. What has traditionally been considered a safe diagnostic procedure—core needle biopsy for early-stage breast cancer—has been reevaluated in light of new data revealing a potential adverse consequence: the acceleration of metastatic progression if surgery is delayed more than 53 days after the biopsy. Far from being anecdotal, this finding is supported by a combination of large-scale clinical data, histopathological analyses, and well-designed experimental models.

The team led by Hiroyasu Kameyama and Takemi Tanaka, in collaboration with institutions such as the Stephenson Cancer Center and Thomas Jefferson University, set out to understand why surgical delays increase mortality in breast cancer patients, even when the tumor is in an early and theoretically curable stage. To do so, they analyzed a cohort of over 176,000 patients diagnosed by needle biopsy and found that, after 53 days post-procedure, the risk of death begins to rise significantly. This increase cannot be explained solely by the natural progression of the tumor, as early-stage (I–II) breast cancer typically advances slowly in most cases. So, what is happening?

The answer seems to lie in the wound left by the biopsy itself. Unlike a lesion in healthy tissue that heals and resolves, the study shows that in a tumor context, this wound remains active for weeks—or even months—creating an inflammatory microenvironment favorable to metastasis. Most notably, there is a persistent accumulation of M2-type macrophages—also known as M2-like or M24 macrophages—surrounding the biopsy needle track. These macrophages are not hostile to the tumor; on the contrary, they support its survival and expansion. They release factors such as VEGF (which stimulates new blood vessel formation) and TGF-β (which induces cancer cells to lose cohesion and gain invasive capacity through epithelial-to-mesenchymal transition, or EMT).

Using mouse models, the researchers observed how a single biopsy increased the number of cancer cells reaching the lungs, translating to systemic dissemination. But the most intriguing part was identifying the biochemical culprit: the enzyme COX-2, which is activated by the trauma of the biopsy and produces prostaglandin E2 (PGE2). This molecule, under the hypoxic conditions of the wound, further promotes M2 polarization and sustains the inflammatory loop via the EP2 receptor. In other words, a feedforward loop is generated, where each component amplifies the next:

COX-2 → PGE2 → EP2 → more M2 → more EMT and angiogenesis → more metastasis.

Beyond demonstrating this mechanism, the authors went a step further. They tested oral inhibitors of COX-2 (like celecoxib) and EP2 (such as PF04418948), which successfully reduced the number of disseminated tumor cells in the lungs of biopsied mice and decreased pro-metastatic changes in mammary tissue. This result opens a concrete therapeutic avenue: if surgery cannot be performed within 53 days of biopsy, administration of these anti-inflammatory agents could be considered as a protective measure.

The magnitude of this finding cannot be underestimated. In modern oncology—where every day gained in diagnosis and treatment counts—knowing that merely waiting after a biopsy can alter a patient’s prognosis forces a reevaluation of certain clinical practices. Current guidelines recommend surgery within 60 days post-diagnosis, but this study suggests that even that threshold may be brushing the edge of safety.

Figure 1. Core needle biopsy triggers COX-2/PGE₂/EP2 signaling, promoting M2 macrophage polarization and secretion of TGF-β1 and VEGF-A. These factors induce EMT, angiogenesis, and systemic dissemination, increasing mortality risk when surgery is delayed.

It is also critical to highlight that the observed effects appear especially relevant in estrogen receptor-positive (ER+) breast cancers, which typically exhibit a more indolent behavior. The fact that even in these tumors aggressive EMT changes are observed following biopsy is a warning sign. The tumor microenvironment—the biological terrain surrounding the cancer—may be more decisive than the tumor’s intrinsic characteristics.

This study does not aim to discourage the use of needle biopsies, an invaluable diagnostic tool. But it does urge us to better understand their invisible side effects. As in many other areas of medicine, it’s not just what we do, but when and how we do it that makes the difference.

Ultimately, this research highlights a fundamental truth: cancer is not just a mass of growing cells, but a dynamic ecosystem that actively responds to every intervention we make. Sometimes, unknowingly, we may be feeding that system. That’s why fully understanding these mechanisms not only helps improve treatments, but also anticipates the consequences of our clinical actions. And in that direction, this study not only opens our eyes—but also new doors for smarter and more effective intervention.

Main Reference: 

Kameyama, H., Dondapati, P., Simmons, R., Leslie, M., Langenheim, J. F., Sun, Y., Yi, M., Rottschaefer, A., Pathak, R., Nuguri, S., Fung, K. M., Tsaih, S. W., Chervoneva, I., Rui, H., & Tanaka, T. (2023). Needle biopsy accelerates pro-metastatic changes and systemic dissemination in breast cancer: Implications for mortality by surgery delay. Cell reports. Medicine, 4(12), 101330. https://doi.org/10.1016/j.xcrm.2023.101330

Other References:

Siegel, R. L., Miller, K. D., Fuchs, H. E., & Jemal, A. (2022). Cancer statistics, 2022. CA: a cancer journal for clinicians, 72(1), 7–33. https://doi.org/10.3322/caac.21708

Early Breast Cancer Trialists’ Collaborative Group (EBCTCG), Davies, C., Godwin, J., Gray, R., Clarke, M., Cutter, D., Darby, S., McGale, P., Pan, H. C., Taylor, C., Wang, Y. C., Dowsett, M., Ingle, J., & Peto, R. (2011). Relevance of breast cancer hormone receptors and other factors to the efficacy of adjuvant tamoxifen: patient-level meta-analysis of randomised trials. Lancet (London, England), 378(9793), 771–784. https://doi.org/10.1016/S0140-6736(11)60993-8

Pan, H., Gray, R., Braybrooke, J., Davies, C., Taylor, C., McGale, P., Peto, R., Pritchard, K. I., Bergh, J., Dowsett, M., Hayes, D. F., & EBCTCG (2017). 20-Year Risks of Breast-Cancer Recurrence after Stopping Endocrine Therapy at 5 Years. The New England journal of medicine, 377(19), 1836–1846. https://doi.org/10.1056/NEJMoa1701830