Colorectal Cancer May Cause Peripheral Neuropathy Before Chemotherapy, New Study Finds
Peripheral neuropathy is usually discussed as a side effect of chemotherapy. A new study suggests the story may be more complicated.
Researchers at The University of Texas MD Anderson Cancer Center found evidence that colorectal cancer itself may cause nerve damage before chemotherapy begins. In mouse models and rhesus macaques with colorectal cancer, researchers identified inflammation, changes in circulating lipids, damage to nerve myelin, immune-cell activity, and impaired nerve function.
The study, “Inflammatory neuropathy in mouse and primate models of colorectal cancer,” was accepted by Nature Communications in August 2026. Importantly, this was preclinical research involving mice and non-human primates, not a clinical trial in people. The findings therefore do not prove that every person with colorectal cancer develops neuropathy. They do, however, offer a possible explanation for earlier clinical observations showing that some colorectal cancer patients have evidence of peripheral nerve dysfunction even before receiving chemotherapy.
For patients and oncologists, that distinction could matter. If cancer has already placed stress on peripheral nerves, subsequent treatment with neurotoxic chemotherapy could potentially add another layer of injury.
What Is Peripheral Neuropathy?
Peripheral neuropathy occurs when nerves outside the brain and spinal cord become damaged or dysfunctional.
Depending on which nerves are affected, symptoms can include:
Numbness or tingling in the hands and feet
Burning, shooting, or electric-like pain
Reduced ability to sense temperature or touch
Muscle weakness
Problems with balance or coordination
Difficulty with fine motor tasks
In oncology, peripheral neuropathy is commonly associated with chemotherapy drugs such as oxaliplatin, paclitaxel, and cisplatin.
The new research raises another possibility: some nerve injury may already be developing because of the cancer itself.
Can Colorectal Cancer Cause Neuropathy Before Chemotherapy?
That was one of the central questions addressed by the researchers.
Previous studies had reported reduced nerve-fiber density and sensory abnormalities in some people with colorectal cancer before chemotherapy. But observational studies cannot easily determine whether cancer caused the neuropathy or whether other factors such as diabetes, alcohol use, or unrelated neurological conditions were responsible.
The MD Anderson researchers therefore used controlled animal models to investigate causality.
Their results suggest that colorectal cancer can produce a subclinical inflammatory neuropathy, meaning nerve abnormalities may exist even when obvious pain symptoms are absent.
That is an important point. Neuropathy does not always begin with pain.
In fact, the researchers note that sensory loss can be an early manifestation of several types of neuropathy. A patient might have underlying nerve dysfunction without experiencing the classic burning or tingling sensations people typically associate with neuropathy.
What Did the Researchers Find?
The study identified several interconnected changes in animals with colorectal cancer.
1. Peripheral nerve fibers were lost
In mice with colorectal tumors, researchers found reduced nerve-fiber density in the skin of both the hind paws and ears.
Because these areas were anatomically distant from the colorectal tumor, the findings suggested that the nerve injury was systemic rather than simply caused by the tumor physically pressing on nearby nerves.
Interestingly, the mice did not show strong evidence of increased sensitivity to touch or temperature.
Instead, the neuropathy appeared relatively subtle.
2. Colorectal cancer affected coordination and movement
Although the mice did not demonstrate dramatic pain hypersensitivity, researchers detected changes in gait and motor coordination.
Tumor-bearing mice showed differences in measures including:
Running speed
Step-cycle timing
Standing time
Swing speed
They also took longer to cross progressively more difficult balance beams.
Treatment with the anti-inflammatory drug carprofen reduced some of the early gait abnormalities, suggesting that inflammation contributed to the neurological changes.
This supports an important distinction: nerve damage may affect coordination and proprioception even when a patient does not report significant pain.
3. Cancer caused major changes in circulating lipids
One of the more intriguing findings involved lipid metabolism.
Researchers analyzed 371 lipid species in the blood plasma of tumor-bearing mice and found substantial changes.
Among them:
13 lipid species were significantly increased.
101 were significantly decreased.
Triglycerides were broadly depleted.
Several inflammation-associated lipid families were elevated.
Long-chain fatty acids were increased while some shorter-chain fatty acids were reduced.
Similar lipid abnormalities were found inside the sciatic nerves themselves.
The authors describe this condition as dyslipidemia, meaning the normal balance of circulating fats and lipid molecules had been disrupted.
When tumor-bearing mice were treated with the anti-inflammatory drug carprofen, many of these lipid abnormalities were reduced. This suggests that tumor-driven inflammation may contribute to the metabolic changes.
4. The protective insulation around nerves was damaged
Peripheral nerves are wrapped in a protective structure called myelin.
A good analogy is insulation surrounding an electrical wire. Damage the insulation and electrical signals may become slower, weaker, or less reliable.
Using electron microscopy, researchers found abnormalities in the myelin surrounding nerves in mice with colorectal cancer.
They observed:
Myelin decompaction
Evidence of Schwann-cell dysfunction
Axonal swelling
Changes consistent with nerve degeneration
Schwann cells are specialized cells responsible for maintaining and repairing peripheral nerve myelin.
The study's microscopy images show substantially more irregular myelin around nerve fibers in tumor-bearing animals compared with controls.
5. Immune cells accumulated around the nerves
Researchers also found increased numbers of macrophages within peripheral nerves and sensory ganglia.
Macrophages are immune cells that respond to inflammation and damaged tissue.
Interestingly, their role appeared complicated.
The tumor environment pushed many macrophages toward a more inflammatory state. However, when researchers experimentally removed macrophages, neurological performance actually became worse.
That suggests macrophages may play both harmful and protective roles during nerve injury.
This is a good example of why inflammation cannot always be reduced to “good” versus “bad.” The immune system is more like an emergency response team. Some activities can cause collateral damage, while others are required for repair.
6. Colorectal cancer disrupted calcium regulation inside nerve cells
The researchers also discovered abnormalities involving ryanodine receptors, cellular channels that help regulate calcium inside nerve cells.
Tumor-associated inflammation increased oxidation of these receptors and reduced their normal regulation.
The result was disrupted calcium storage and signaling inside sensory neurons.
Why does that matter?
Calcium is essential for normal nerve-cell communication. When calcium regulation becomes dysfunctional, neurons may have difficulty transmitting electrical signals normally.
Researchers subsequently measured electrical activity in sensory neurons and found reduced spike amplitude and altered activity in cells taken from tumor-bearing mice.
Taken together, these findings provide a potential biological chain connecting cancer-associated inflammation with actual nerve dysfunction.
Similar Nerve Damage Was Found in Rhesus Macaques
One of the study's strengths is that the researchers did not rely exclusively on mice.
They also examined archived samples from rhesus macaques that spontaneously developed colorectal cancer.
The animals with colorectal cancer showed many of the same abnormalities seen in mice, including:
Changes in circulating lipid profiles
Elevated inflammatory molecules
Inflammatory-cell infiltration into peripheral nerves
Axonal degeneration
Increased macrophage-related activity
Evidence of nerve regeneration following injury
For example, structures known as Büngner bands, which are created by Schwann cells as nerves attempt to regenerate after damage, were found in 11 of 15 colorectal cancer samples compared with only 1 of 7 control samples.
Finding similar patterns across two species strengthens the biological argument that colorectal cancer may contribute directly to peripheral nerve injury.
But it still does not replace human clinical studies.
Why This Could Matter for Chemotherapy-Induced Peripheral Neuropathy
Perhaps the most clinically interesting implication involves what happens next.
Certain chemotherapy drugs can cause chemotherapy-induced peripheral neuropathy (CIPN).
For colorectal cancer patients, oxaliplatin is particularly relevant because it is frequently used in colorectal cancer treatment and is well known for causing neuropathy.
Pre-existing neuropathy is already recognized as a risk factor for developing chemotherapy-induced peripheral neuropathy.
The researchers therefore propose a possible “priming” effect.
In simplified terms:
Colorectal cancer → systemic inflammation and metabolic changes → subtle nerve injury → chemotherapy adds additional neurotoxic stress → increased possibility of persistent neuropathy.
The study does not prove that this sequence occurs in patients. The authors explicitly identify this as something future studies need to investigate.
But the hypothesis could change how researchers think about chemotherapy-related neuropathy.
Instead of viewing chemotherapy as the starting point of nerve damage, cancer itself may sometimes represent the first hit.
What Does This Study Mean for Colorectal Cancer Patients?
Patients should not interpret these findings as evidence that colorectal cancer automatically causes neuropathy.
Several important limitations remain.
First, this was primarily an animal study.
Second, the researchers studied particular models of colorectal cancer, including tumors associated with mismatch-repair deficiency and microsatellite instability.
Third, researchers still do not know how frequently this type of subclinical neuropathy occurs in people with colorectal cancer.
Finally, they do not yet know whether identifying or treating cancer-associated nerve inflammation before chemotherapy would reduce subsequent chemotherapy-induced neuropathy.
Those questions require human clinical research.
Still, the study suggests that clinicians and researchers may want to pay closer attention to neurological function before cancer treatment begins, rather than assuming all neuropathy detected during treatment was caused by chemotherapy.
Cancer Treatment Side Effects May Start With More Than Treatment
One of the broader lessons from this research is that the line between the effects of cancer and the effects of cancer treatment is not always clean.
Cancer can alter inflammation, metabolism, immune signaling, nutritional status, gastrointestinal function, and potentially the nervous system long before chemotherapy is administered.
The authors propose a multi-step model in which colorectal tumors drive inflammation and abnormal lipid metabolism. Those changes contribute to oxidative stress, immune-cell infiltration, impaired calcium regulation, Schwann-cell dysfunction, and ultimately nerve damage and sensorimotor impairment.
That model will need additional testing in humans.
But if it holds up, it could eventually influence how researchers approach the prevention and management of chemotherapy-induced peripheral neuropathy.
The Bottom Line
A new Nature Communications study provides evidence that colorectal cancer itself may contribute to peripheral neuropathy before chemotherapy begins.
In mice and rhesus macaques, colorectal cancer was associated with inflammation, abnormal lipid metabolism, immune-cell accumulation, myelin damage, altered calcium signaling, and impaired nerve function.
The research does not establish that the same process occurs in every colorectal cancer patient. It also does not provide a new treatment for neuropathy.
What it does provide is a compelling biological hypothesis: some patients may enter chemotherapy with nerves that are already under stress.
That could be important because pre-existing neuropathy is a known risk factor for chemotherapy-induced peripheral neuropathy.
Future human studies will be needed to determine how common cancer-associated neuropathy is, whether it predicts chemotherapy-related nerve damage, and whether identifying it earlier could ultimately help protect patients during treatment.
FAQs
Can colorectal cancer cause neuropathy before chemotherapy?
Preclinical research suggests that colorectal cancer itself may contribute to peripheral neuropathy before chemotherapy begins. In mouse and rhesus macaque models, researchers found nerve-fiber loss, inflammation, myelin damage, altered lipid metabolism, and impaired nerve function. Human studies are still needed to determine how commonly this occurs in patients.
What is chemotherapy-induced peripheral neuropathy?
Chemotherapy-induced peripheral neuropathy, or CIPN, is nerve damage caused by certain chemotherapy drugs. Symptoms can include numbness, tingling, burning pain, weakness, and problems with balance or coordination.
Why could pre-existing neuropathy matter before chemotherapy?
Pre-existing neuropathy is a known risk factor for chemotherapy-induced peripheral neuropathy. The study raises the possibility that colorectal cancer may “prime” peripheral nerves before treatment, potentially making them more vulnerable to later neurotoxic stress.
Did the study show that colorectal cancer causes neuropathy in humans?
No. The study was conducted primarily in mice and rhesus macaques. The findings suggest a biological mechanism that should now be investigated in people with colorectal cancer.
How might colorectal cancer damage peripheral nerves?
The researchers propose that tumor-driven inflammation and abnormal lipid metabolism may contribute to oxidative stress, immune-cell infiltration, Schwann-cell dysfunction, myelin damage, altered calcium signaling, and impaired nerve function.
Does colorectal cancer neuropathy always cause pain?
Not necessarily. In the study, nerve damage occurred without strong pain hypersensitivity. This suggests that neuropathy may sometimes be subclinical, meaning nerve dysfunction is present before obvious symptoms appear.
Could this affect how colorectal cancer patients are evaluated before chemotherapy?
Potentially, but more human research is needed. If future studies confirm that some patients have nerve damage before treatment, baseline neurological assessment could become more important when evaluating the risk of chemotherapy-induced peripheral neuropathy.
Reference
Inflammatory neuropathy in mouse and primate models of colorectal cancer
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This blog was reviewed by Dr. Sourabh Kharait.
This blog is for educational purposes only and is not intended as medical advice. Always consult with your healthcare provider before making any changes to your treatment plan, hydration strategies, or diet. The information provided here is based on general insights and may not apply to individual circumstances.
