This study aims to evaluate whether a combination of oral zinc supplementation and transdermal clobetasol cream is effective in preventing and reducing the severity of hand-foot skin reaction (HFSR) induced by regorafenib treatment.

HFSR is one of the most common adverse effects of regorafenib, affecting more than 50% of patients, with 10-15% experiencing severe Grade 3 toxicity. Clobetasol, a high-potency corticosteroid, has been shown to significantly reduce the severity of HFSR when used preemptively rather than reactively. Additionally, recent clinical trials indicate that oral zinc supplementation may further reduce the incidence of Grade ≥2 HFSR.

This prospective, non-randomized interventional study will compare three treatment groups:

Oral zinc supplementation + transdermal clobetasol cream Transdermal clobetasol cream alone Oral zinc supplementation alone The study will assess the effectiveness of these treatments using CTCAE grading, the Hand-Foot Syndrome Scale-14, and quality of life measures (FACT-G, fatigue, and anxiety/depression scales). Additionally, the study will evaluate the impact of HFSR on treatment adherence, regorafenib dose modifications, and overall survival.

The study will enroll approximately 120 patients across multiple centers in Türkiye.

Background and Rationale Hand-foot skin reaction (HFSR) is a common dose-limiting toxicity associated with regorafenib treatment, occurring in more than 50% of patients and leading to treatment modifications in up to 15% of cases. Despite its clinical significance, no standardized prophylactic strategy exists.

High-potency topical corticosteroids, such as clobetasol propionate 0.05%, have demonstrated efficacy in reducing HFSR severity, particularly when used preemptively. Additionally, recent studies suggest that oral zinc supplementation may contribute to maintaining skin integrity and reducing inflammatory responses, thereby mitigating HFSR severity. However, the comparative efficacy of these interventions and their potential synergistic effect have not been well established.

Study Objectives This study aims to evaluate whether oral zinc supplementation and/or transdermal clobetasol cream effectively prevent and reduce the severity of regorafenib-induced HFSR, thereby improving treatment adherence and patient quality of life.

Study Design

This is a prospective, non-randomized, interventional study involving approximately 120 patients receiving regorafenib at multiple oncology centers in Türkiye. Participants will be assigned to one of three intervention arms based on their treating physician's discretion:

Oral zinc supplementation + transdermal clobetasol cream Transdermal clobetasol cream alone Oral zinc supplementation alone Interventions Oral Zinc Supplementation: 78 mg zinc gluconate, administered twice daily for 8 weeks.

Transdermal Clobetasol Cream: Clobetasol propionate 0.05%, applied twice daily to the palms and soles for 8 weeks.

Assessment & Follow-up HFSR severity and incidence will be evaluated using CTCAE v5.0 criteria. Patient-reported outcomes will be assessed via Hand-Foot Syndrome Scale-14 (HFS-14) and FACT-G quality of life questionnaire.

Regorafenib adherence (dose modifications, treatment discontinuations) will be monitored.

Survival analysis (PFS and OS) will be conducted at 6 months. By comparing these prophylactic strategies, this study seeks to identify the most effective approach to minimize HFSR burden in patients undergoing regorafenib therapy, potentially influencing future clinical practice.

Inclusion Criteria:

• Age ≥18 years
• Histologically confirmed solid tumor for which regorafenib is an approved treatment (e.g., metastatic colorectal cancer, gastrointestinal stromal tumor, hepatocellular carcinoma, glioblastoma, or others)
• Initiating regorafenib treatment for the first time
• ECOG performance status of 0-2
• Baseline hand-foot skin reaction (HFSR) of Grade 0 (no prior HFSR symptoms) according to CTCAE v5.0
• Adequate organ function, including:

AST/ALT ≤ 3× upper limit of normal (ULN) Creatinine clearance > 50 mL/min Hemoglobin ≥ 9 g/dL Platelet count ≥ 75,000/mm³

• Able to tolerate oral zinc supplementation and/or topical corticosteroids
• Willing to participate and provide informed consent

Exclusion Criteria:

• Pre-existing dermatologic conditions affecting the hands or feet (e.g., psoriasis, eczema, active infections)
• Prior Grade ≥1 HFSR from any VEGFR-TKI therapy
• Allergy or known hypersensitivity to zinc, clobetasol, or other study components

Individual participant data (IPD) will not be shared due to privacy regulations and institutional policies. Data access is restricted to the study team and authorized personnel to ensure compliance with ethical guidelines and patient confidentiality