Toxicity Due to Chemotherapy

Fluoropyrimidines (FLU) are drugs widely used in chemotherapy for various tumors, such as breast, colon, rectal, and gastric cancers. FLU is a drug that inhibits thymine synthesis and, consequently, DNA synthesis, leading to tumor cell death. However, up to 30% of patients treated with FLU experience severe toxicities, depending on the dose and regimen received. The most common symptoms include mucositis, vomiting, nausea, diarrhea, and neutropenia. The enzyme dihydropyrimidine dehydrogenase (DPD) plays a key role in FLU metabolism. Patients with mutations in the DPYD gene (which encodes DPD) are at high risk of experiencing severe toxicities from FLU. Uridine triacetate (UT) is a drug that can be used as an antidote for 5-FU in patients who develop severe toxicities. However, despite its efficacy, it is expensive and not commercially available in Brazil. Currently, the Brazilian population has no access to an antidote for the treatment of FLU-related toxicities. This Phase I/II study will evaluate the dose, safety, and efficacy of compound the association of two molecules as an antidote for grade 3 or higher toxicities resulting from the use of FLU.

The goal of this clinical trial is to learn about the effect of sarcopenic status on the occurrence of treatment-related toxicity during the first course of anti-cancer treatment in several types of cancers. The main question it aims to answer is : Is sarcopenia a predictive marker for the occurrence of toxicity in the initial phase of cancer treatment? The evaluation will focus on the body composition of the participants, assessed by impedancemetry, and on their muscular performance by standardized physical tests.

The goal of this observational study is to learn how gonadotoxic treatments (chemotherapies, radiotherapies or immunotherapies) affect the fertility status of participants with cancer. The main questions it aims to answer are: * in females, if cancer therapies reduce the Anti-Müllerian hormone (AMH) concentration (ovarian reserve); * in males, if cancer therapies reduce sperm concentration (sperm quality).