Phase II Biomarker Trial of Low-Dose Tamoxifen and Lifestyle Interventions for Breast Cancer Prevention in High-Risk Women

The primary objective of the study is to determine whether **Low Dose Tamoxifen (LDT)** increases circulating **Sex Hormone Binding Globulin (SHBG)** more effectively than lifestyle intervention (LI), with or without intermittent caloric restriction (ICR), after a 6-month intervention period. This is clinically relevant as increased SHBG levels may be associated with a reduced risk of breast cancer, providing a potential preventive strategy for women at increased risk.

Secondary objectives include:

• To assess whether ICR significantly modulates main and secondary endpoints such as the **HOMA-index**, inflammatory markers, lipid profile, Adiponectin/Leptin (A/L) ratio, quality of life (QoL), **Body Mass Index (BMI)**, body composition, safety, and toxicity.
• To evaluate whether LDT significantly affects secondary endpoints, including the HOMA-index, immune and inflammatory markers, lipid profile, A/L ratio, QoL, BMI, fat body composition, safety, and toxicity.
• To investigate differences in microbiome composition between study arms and the impact of microbiome changes on QoL, considering circulating biomarkers, cytokines, immune modulators, and inflammatory proteins in serum.
• To examine changes in **Mammographic Breast Density (MD)** by LDT versus LI, with or without ICR, in a subgroup of participants, as not all participants will undergo mammography due to age considerations.

The clinical trial involves **healthy women** aged 18 to 70 years, who are either carriers of a germline pathogenic variant such as **BRCA1**, BRCA2, PALB2, ATM, CHEK2, CDH1, RAD51C, or RAD51D, or have a breast cancer risk greater than 5% over 10 years according to the Tyrer-Cuzick model or the Breast Cancer Surveillance Consortium Risk models. Additionally, participants may have a history of previously treated breast intraepithelial neoplasia. The study population is exclusively female, with no male participants included, and it involves a vulnerable population. The sponsor has not provided the total number of participants. Selection criteria include the ability to understand and sign a written informed consent document, and an ECOG performance status of 1 or less. Participants are required to have a negative mammogram or other radiological imaging based on age and center protocol screening within six months before the baseline visit, or a bilateral mammogram within 12 months for those in the IEN strata. A negative transvaginal ultrasound or hysteroscopy within six months before the baseline visit is also required, except for women with a previous hysterectomy due to a benign condition. Lifestyle considerations such as diet and physical activity are not specified in the provided data.

The clinical trial is designed as a **randomized**, **double-blind**, controlled study to evaluate the effects of low-dose **tamoxifen citrate** on circulating Sex Hormone Binding Globulin (SHBG) levels in women at increased risk of breast cancer. The trial will involve healthy women aged 18 to 70 who are either carriers of a germline pathogenic variant in specific genes (BRCA1, BRCA2, PALB2, ATM, CHEK2, CDH1, RAD51C, or RAD51D) or have a breast cancer risk greater than 5% over ten years, or have been previously treated for breast intraepithelial neoplasia. The study is expected to run from June 2023 to January 2026, with participant involvement lasting approximately six months.

Participants will be randomly assigned to one of four intervention arms, which include low-dose tamoxifen, lifestyle intervention, or a combination of both, with or without intermittent caloric restriction. The trial will commence with a screening visit to confirm eligibility based on inclusion criteria, such as age, genetic risk factors, and recent negative mammogram or ultrasound results. Following successful screening, participants will undergo baseline assessments before starting the intervention.

Study visits will occur at regular intervals throughout the trial to monitor safety, adherence, and the primary endpoint, which is the post-intervention level of circulating SHBG. Secondary endpoints include changes in serum biomarkers, safety and toxicity, quality of life, body mass index (BMI), body composition, microbiome composition, and immune modulation. The end-of-study visit will involve final assessments and data collection to evaluate the outcomes of the interventions.

Participants may be withdrawn from the study if they experience adverse events, fail to comply with the study protocol, or choose to withdraw consent. The trial's design ensures that data collected will contribute to understanding the potential benefits of low-dose tamoxifen and lifestyle changes in reducing breast cancer risk among high-risk populations.

The clinical trial involves the administration of **Nolvadex**, a pharmaceutical product containing the active substance **tamoxifen citrate**. This medication is provided in the form of a **film-coated tablet**. Each tablet contains 10 mg of tamoxifen citrate. The route of administration is **oral use**, and the maximum daily dose is set at 10 mg. The total maximum dose over the treatment period is 1050 mg, with a maximum treatment duration of 7 days. The product is manufactured by AstraZeneca S.p.A. and is not formulated for pediatric use. The active substance, tamoxifen citrate, is of chemical origin and is classified under the ATC code L02BA01, indicating its use in hormonal therapy.

In addition to the experimental treatment with Nolvadex, the study includes a lifestyle intervention (LI) as a non-experimental treatment. This intervention may be combined with or without intermittent caloric restriction (ICR) to assess its impact on circulating Sex Hormone Binding Globulin (SHBG) levels. The trial aims to compare the effects of low-dose tamoxifen with these lifestyle modifications over a 6-month period. Participant compliance with the dosing schedule and lifestyle interventions will be monitored throughout the study to ensure adherence to the protocol.

Efficacy in the clinical trial titled "Low dose TamOxifen and LifestylE changes for bReast cANcer prevenTion: a randomized phase II biomarker trial in subjects at increased risk (TOLERANT Study)" will be assessed primarily by measuring the post-intervention levels of circulating **Sex Hormone Binding Globulin (SHBG)**. This primary endpoint will be evaluated to determine the effect of Low Dose Tamoxifen (LDT) compared to lifestyle intervention (LI) with or without intermittent caloric restriction (ICR) after a 6-month intervention period.

Secondary endpoints include changes over time in various serum biomarkers such as SHBG, insulin, glucose, lipid profile, IGF-I, IGFBP-1, -2, and -3, hs-CRP, adiponectin, and leptin. Additionally, the trial will assess changes in safety and toxicity, quality of life, BMI and body composition, microbiome composition, and immune modulation by expression of inflammation cell signaling genes. These parameters will be collected and analyzed at specified timepoints throughout the study to provide a comprehensive evaluation of the intervention's efficacy.