Study on the Safety and Tolerability of Postoperative Radiotherapy Concurrent With CDK4/6 Inhibitors in HR+/HER2- High-Risk Breast Cancer

NCT07446686 | Not Yet Recruiting Early Phase 1

• 1 other identifier: 2025-169
• Study Type: interventional
• Target: 30
• Locations: 0 countries
• Sites: N/A

Brief Summary

The investigators combined postoperative radiotherapy with CDK4/6 inhibitors ± endocrine adjuvant therapy to explore the tolerability and safety of this treatment regimen in HR+/HER2- postoperative high-risk breast cancer patients. During the study, investigators also utilized PRO scales (FACT-B, FACT-ES, FACT-F) to evaluate patients' multidimensional experiences, such as physical function, emotional state, and treatment-related symptoms, thereby obtaining more authentic and reliable data for symptom assessment and patient benefit.

Conditions

Breast Cancer

Outcome Measures

Primary Outcomes (1)

• tolerability and safety

  This study aims to investigate the tolerability and safety of postoperative adjuvant radiotherapy combined with CDK4/6 inhibitors in the treatment of hormone receptor-positive, HER2-negative high-risk breast cancer patients. Safety will be expressed by the incidence (%) of grade 3 and above adverse events during the course of treatment. Tolerability is expressed by the maximum dose (mg) of CDK4/6 inhibitor that the patient can use during the combination therapy.

  From enrollment to 3 months after the end of radiotherapy

Secondary Outcomes (1)

• To assess the impact of this combination regimen on patient quality of life

  Start of radiotherapy to 3 months after radiotherapy

Study Arms (1)

Radiotherapy with concurrent CDK4/6 inhibitors combined with endocrine therapy

EXPERIMENTAL

After the patient is confirmed to be enrolled, the CDK4/6i dose for the next patient is determined by a dose allocation model (empirical logistic model, obtained using the R dfcrm software package) based on the DLT observed in all previously evaluated patients. The starting dose of CDK4/6i (abexiclib, oral) is 50 mg bid, and other dose levels are: 100 mg bid, 150 mg bid.

Drug: CDK4/6 inhibitor±endocrine therapy drug±OFS treatment combined with synchronous radiotherapy

Interventions

CDK4/6 inhibitor±endocrine therapy drug±OFS treatment combined with synchronous radiotherapy DRUG

After the patient is confirmed to be enrolled, the CDK4/6i dose for the next patient is determined by a dose allocation model (empirical logistic model, obtained using the R dfcrm software package) based on the DLT observed in all previously evaluated patients. The starting dose of CDK4/6i (abexiclib, oral) is 50 mg bid, and other dose levels are: 100 mg bid, 150 mg bid.

Radiotherapy with concurrent CDK4/6 inhibitors combined with endocrine therapy

Eligibility Criteria

• Age: 18 Years - 75 Years
• Sex: female
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Age is 18-75 years old, gender is female
• Postoperative pathological examination confirmed HR+, HER2- invasive breast cancer:
• ER positivity and/or PR positivity is defined as: all positively stained tumor cells The proportion of tumor cells is ≥10%;
• HER2 negativity is defined as: 0/1+ by standard immunohistochemistry (IHC) test; ISH test was negative.
• The time from radical surgery or breast-conserving surgery to randomization shall not exceed 6 months;
• Postoperative pathological examination after radical surgery revealed the presence of lymph nodes in the axilla on the ipsilateral side of the breast lesion.
• Metastasis (lymph node micrometastases, ipsilateral internal mammary lymph nodes and supraclavicular lymph nodes are allowed) metastasis, but the number of metastases to the ipsilateral internal mammary lymph nodes and supraclavicular lymph nodes is not included in the positive calculation of sexual lymph nodes), the specific requirements are as follows:
• \) The number of lymph node metastases is ≥ 4; 2) When the number of lymph node metastases is 1 to 3, at least one of the following high-risk factors must be met: i. Postoperative pathological examination shows that the diameter of the primary tumor is ≥5cm; ii. The histological grade of the primary tumor is grade III (excluding grade II-III); iii. There is residual invasive cancer in breast lesions after neoadjuvant treatment; iv. Ki-67≥30%.
• Eastern Cooperative Oncology Group (ECOG) physical status score is 0 -2 points.
• With my consent and having signed the informed consent form, I am willing and able to comply with the planned interview.
• inspections, study treatment plans, laboratory tests, and other research procedures.

You may not qualify if:

• Pathological examination diagnosed as HER2-positive breast cancer (HER2-positive definition: standard immune Histochemistry (IHC) test is 3+ or ISH test is positive).
• Local or regional recurrence of breast malignant tumors.
• The clinical stage of the tumor is stage IV (metastatic) breast cancer.
• Bilateral breast cancer (including contralateral carcinoma in situ).
• History of serious lung diseases such as interstitial pneumonia.
• Have received CDK4/6 inhibitor treatment or other anti-tumor biological treatments in the past therapy, targeted therapy or tumor immunotherapy.
• Have undergone major surgical operations, any investigational drugs, or others within 4 weeks before randomization Anticancer treatment or use of immunomodulators (excluding surgery, chemotherapy, radiotherapy and endocrine therapy).
• The presence of other serious physical or mental illnesses or laboratory abnormalities that may increase participation The risks of the research, or interference with the research results, and the researcher's opinion that he is not suitable to participate in this research study patients.

Sponsors & Collaborators

• Guizhou Provincial People's Hospital: lead

MeSH Terms

Conditions

Breast Neoplasms

Condition Hierarchy (Ancestors)

Neoplasms by Site; Neoplasms; Breast Diseases; Skin Diseases; Skin and Connective Tissue Diseases

Central Study Contacts

Yong Li

CONTACT

86-13628566285; liyong7229771@163.com

Study Design

• Study Type: interventional
• Phase: early phase 1
• Allocation: NA
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: SINGLE GROUP
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: November 22, 2025
• First Posted: March 3, 2026
• Study Start: April 1, 2026
• Primary Completion (Estimated): April 30, 2027
• Study Completion (Estimated): June 30, 2027
• Last Updated: March 3, 2026

Record last verified: 2026-02

Data Sharing

• IPD Sharing: Will not share