Different Chemotherapy Drugs Leave Different Fingerprints on the Brain’s Networks

Chemotherapy saves millions of lives every year, but a growing body of research suggests that the drugs that attack tumors may also quietly reshape the brain. A new resting-state functional MRI study, published in BMC Medical Imaging, offers one of the most detailed looks yet at how two widely used chemotherapy strategies, fluorouracil-based regimens given for colorectal cancer and carboplatin-based regimens given for non-small cell lung cancer, are associated with distinct patterns of altered communication among large-scale brain networks. The findings come from a team led by Yong Hu and Siwen Liu, with corresponding authors Zhengxiang Han and Xiaobing Qin, based at Xuzhou Medical University and Jiangsu Cancer Hospital in China.

The question the researchers set out to address is deceptively simple: do different chemotherapy regimens leave different signatures on brain function? This matters because so-called chemotherapy-related cognitive impairment, often described by patients as brain fog, has mostly been studied as a single phenomenon, as if all cytotoxic drugs affected the brain in the same way. If different regimens produce measurably different network alterations, that could eventually help clinicians predict which patients are most at risk and open the door to regimen-specific protective strategies. The authors are careful, however, to frame their results as regimen-associated associations rather than proof of direct causation, because the two patient groups differed not only in their drugs but also in their cancer types, metastatic patterns, and specific treatment combinations.

To probe the brain’s wiring, the team enrolled 43 colorectal cancer patients who had completed two to three months of fluorouracil-based chemotherapy and 54 non-small cell lung cancer patients who had received two to three months of carboplatin-based chemotherapy. At the end of treatment, each participant underwent resting-state functional MRI, a technique that records spontaneous, low-frequency fluctuations in blood-oxygen signals while the subject simply lies still in the scanner. Because these fluctuations are synchronized across regions that work together, the timing patterns can be used to reconstruct the brain’s functional connectome, a map of which areas are talking to which.

The first analytical approach was graph theory, a branch of mathematics that treats the brain as a network of nodes and edges. Each region of a standardized brain parcellation becomes a node, and the statistical correlation between its activity and that of other regions defines the edges. From this network the researchers computed nodal metrics such as degree, a measure of how many strong connections a region maintains, and global efficiency, which captures how easily that region can exchange information with the rest of the network. When the two patient groups were compared, one result stood out after correction for multiple comparisons, the statistical safeguard that guards against false positives when thousands of brain regions are tested simultaneously.

That robust finding centered on the left precuneus, a hub tucked into the medial parietal cortex that plays a central role in self-referential thought, memory retrieval, and consciousness itself. Patients treated with carboplatin-based chemotherapy showed decreased nodal degree and decreased nodal global efficiency in the left precuneus compared with patients who had received fluorouracil-based treatment. In plain terms, this key integrative hub appeared less connected and less efficient at relaying information in the carboplatin group. Because this result survived multiple comparison correction, the authors consider it the most reliable signal in the study, and it points to carboplatin-based regimens being associated with more pronounced topological alterations in this region.

The second line of analysis used group independent component analysis, a data-driven method that decomposes whole-brain signals into spatially coherent networks without imposing a prior template. This procedure identified the canonical resting-state networks familiar to systems neuroscientists, including the default mode network in its dorsal and ventral subdivisions, the salience network, the left and right executive control networks, the sensorimotor network, the language network, the auditory network, and the primary visual network. The researchers then examined how strongly these networks communicated with one another, both in a static sense, averaged across the entire scan, and dynamically, by tracking how connectivity patterns shift from moment to moment across short sliding windows.

The static connectivity comparisons revealed a pattern of reduced communication in the colorectal cancer group. Patients who had received fluorouracil-based chemotherapy showed decreased connectivity within the right cuneus, part of the precuneus network, and reduced inter-network connectivity between the dorsal default mode network and the salience network, between the dorsal default mode network and the language network, between the ventral default mode network and the primary visual network, and between the sensorimotor network and the primary visual network. The default mode network, which is active when the mind wanders and reflects, and the salience network, which decides which stimuli deserve attention, are both repeatedly implicated in cognitive complaints after cancer treatment, so a weakening of the bridge between them is intriguing.

The dynamic analysis added a temporal dimension that static measures cannot capture. By clustering the sequence of connectivity states across time, the team identified four recurring brain states, each representing a distinct temporary configuration of network communication. Patients in the fluorouracil group spent less time in one particular configuration, showing decreased mean dwell time and a reduced fraction of windows in State 2. Within that state, the colorectal cancer patients displayed increased dynamic connectivity between the salience network and the right executive control network, and between the sensorimotor network and the language and primary visual networks, alongside decreased dynamic connectivity involving the left executive control network with the sensorimotor, auditory, and visual networks, and the right executive control network with the sensorimotor network. These shifting patterns suggest that the two regimens are associated not just with different average levels of connectivity but with different styles of moment-to-moment network reconfiguration.

The authors are explicit about the hierarchy of confidence in their results. The graph theory findings, having survived multiple comparison correction, are described as more robust, whereas the static and dynamic functional network connectivity results are presented as exploratory and in need of independent validation. They also stress the limits imposed by clinical reality: the study compared patients with different cancers, different metastatic patterns, and multiple regimens within each group, so it cannot isolate the pharmacological effect of carboplatin versus fluorouracil from the effects of the underlying disease. What the study does establish is that the two groups, defined by their treatment regimens, show measurably different brain network architectures at the end of therapy, a result consistent with the idea that chemotherapy-related brain changes are not uniform across drug classes.

For patients and clinicians, the significance of this work lies in its direction rather than its immediate application. The precuneus alterations associated with carboplatin-based treatment and the widespread default mode, salience, and executive network changes associated with fluorouracil-based treatment provide concrete, imaging-based targets that future longitudinal studies can follow from before chemotherapy through recovery. If larger, better-controlled cohorts confirm that specific regimens produce specific network signatures, resting-state MRI could eventually become a practical surveillance tool for the brain during cancer care, helping to identify which survivors need cognitive support and guiding the design of regimens that treat the tumor while sparing the mind. The study, approved by the Ethical Commission of Jiangsu Cancer Hospital and conducted under the Declaration of Helsinki, is open access, allowing researchers worldwide to build on its graph-theoretic and independent component analysis framework.

Subject of Research: Differential effects of fluorouracil-based versus carboplatin-based chemotherapy on resting-state functional brain networks in colorectal and lung cancer patients

Article Title: Distinct functional brain network alterations associated with 5-fluorouracil- and carboplatin-based chemotherapy regimens in CRC and NSCLC patients: a combined graph theory and group ICA study based on rs-fMRI

Article References: Distinct functional brain network alterations associated with 5-fluorouracil- and carboplatin-based chemotherapy regimens in CRC and NSCLC patients: a combined graph theory and group ICA study based on rs-fMRI. (n.d.). https://doi.org/10.1186/s12880-026-02823-0

Image Credits: AI Generated

DOI: 10.1186/s12880-026-02823-0

Keywords: chemotherapy, cognitive impairment, resting-state fMRI, graph theory, independent component analysis, precuneus, default mode network, salience network, colorectal cancer, non-small cell lung cancer, 5-fluorouracil, carboplatin