Role of Silymarin in Chemotherapy Toxicity and Cognition Improvement in Breast Cancer Patients

Breast cancer represents the most frequently diagnosed malignancy and the second most common cause of cancer death worldwide. In Egypt, breast cancer is the most common malignancy in women, accounting for 38.8% of cancers in this population, with the estimated number of breast cancer cases nearly 22,700 in 2020 and forecasted to be approximately 46,000 in 2050 .

Paclitaxel and doxorubicin are cytotoxic agents that are commonly used for treatment of breast cancer. Despite their effectiveness, both paclitaxel and doxorubicin are associated with cumulative and potential neurotoxicity and cardiotoxicity respectively . Paclitaxel induced peripheral neuropathy (PN) is a consequence of activation of the inflammatory cascade with subsequent increased pro-inflammatory cytokines production including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) . Moreover, paclitaxel can up-regulate matrix metalloproteinase-3 (MMP3) which plays an important role in the inflammatory and degenerative processes following nerve injury .

Oxidative stress plays a critical role in doxorubicin associated cardiotoxicity through direct cellular damage, induction of apoptosis and activation of nuclear factor- Kabba B (NF-ĸB) which in turn stimulates the production and release of inflammatory mediators .

Hepatotoxicity from doxorubicin was reported and it is likely due to direct toxic injury to the liver. Doxorubicin and its analogues are metabolized in the liver via microsomal enzymes, and production of a toxic or immunogenic intermediate may trigger liver injury with subsequent elevation of Serum aminotransferase.In addition, it was reported that, doxorubicin related hepatotoxicity is a consequence of free radical formation and oxidative stress and antioxidants may protect against doxorubicin-induced toxicity in the liver .

Although, the underlying neuro-protective mechanism of silymarin is mainly due to its capacity to inhibit oxidative stress in the brain, it also confers additional neuro-protection by influencing other pathways such as inflammatory pathways . Silymarin has been implicated in protecting neurons against oxidative stress and nitrosative stress . Silymarin was reported to exert direct effect on neuronal oxidant status .

Silymarin administration in a lipopolysaccharide induced animal model of peripheral neuropathy prevented the dopaminergic neuro-degeneration through inhibiting the activation of microglia. Other in-vitro studies revealed that, silymarin attenuates the activation of glial cell activation in cellular models possibly through inhibition of inducible nitric oxide synthase (iNOS) production . Silymarin was also reported to protect both microglia and astroglia from oxidative insults induced by peroxide in ex vivo system .

Treatment with silymarin prevents the increase in AST and creatine kinase (CK) serum activity and myocardial excitability in rats caused by doxorubicin . It also significantly reduces doxorubicin-pro-oxidative activity and decreases histological changes in liver and heart tissue . The hepato-protective and cardio-protective effects of silymarin may be attributed to its antioxidant capacity, its ability to prevent lipid peroxidation and its ability to increase glutathione concentration .

Cognitive impairment in patients with breast cancer began to appear in the literature in the 1990s, coincident with the increasing use of postoperative adjuvant chemotherapy . In two recent preclinical studies, silymarin was reported to improve cognitive impairment in mice, and these former studies suggested that silymarin may be a therapeutic agent for cognitive decline .

This study will be a randomized placebo controlled parallel study. The study will be performed in accordance with the ethical standards of Helsinki declaration in 1964 and its later amendments.

Group one: (Placebo group; n=28) which will receive four cycles of AC regimen (doxorubicin and cyclophosphamide; each cycle was given every 21 day) followed by 12 cycles of paclitaxel (each cycle was given in a weekly basis) plus placebo tablets once daily.

Group two: (Silymarin group; n=28) which will receive the same regimen plus silymarin 140mg once daily.

• Blood sample collection and biochemical assessment:

1. N-terminal prohormone of brain naturetic peptide (NT-proBNP" ) and liver panel.
2. myeloperoxidase (MPO)
3. neurofilament light chain (NFL)
4. andnuclear factor- Kabba B p65 (NF-ĸB p65) or TNF-alpha

• Clinical assessment of chemotherapy induced toxicities:
• Doxorubicin related cardiotoxicity will be assessed through - Echocardiography at baseline and after the last doxorubicin/ cyclophosphamide (AC) cycle.
• Paclitaxel induced peripheral sensory neuropathy will be done through: - The implication of National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE, Version 5, 2017) for grading of neuropathy at baseline and by the end of every two paclitaxel cycles.
• The use of Neurotoxicity- 12 item questionnaire score (Ntx-12) from the validated Functional Assessment of Cancer Therapy/Gynecologic Oncology Group "FACT/GOG-Ntx-12" at baseline and by the end of every two paclitaxel cycles.
• The assessment of the severity of neuropathic pain through brief pain inventory short form "BPI-SF" worst item. Severity of neuropathic pain will be assessed at baseline and by the end of every two paclitaxel cycles.
• Cognitive impairment will be assessed using the brief assessment of impaired Cogentin questionnaire (BASIC-Q).
• Primary and secondary outcomes:

The primary outcome is the change in ejection fraction and percentage of patients with peripheral sensory neuropathy grade ≥ 2 with the variation of both 12-item neurotoxicity questionnaire (Ntx-12) total score and pain rating scale score. The secondary outcome is the changes in serum levels of the measured biological markers.

• Sample size calculation: According to the results of a previous study, the total number of subjects required to detect the cardio-protective effect of silymarin in patients with different types of cancer receiving anthracyclines containing chemotherapy was 25 patients . With 5% significance level, 80% statistical power and an attrition rate of 10%, the initial sample size required for the current study is 28 patients in each group.

-Ethical approval: The study will be approved by the Research Ethics Committee of Tanta University. The study will be registered as a clinical trial at ClinicalTrials.gov. All participants will be informed about the benefits and risks of the study. Any unexpected risks that will appear during the course of the research will be clarified to the participants and to the ethical committee on time. The data of the enrolled patients will be confidential. All enrolled patients will give their written informed consents. The study will be conducted between October 2022 and October 2024.