Omitting the extra tumor‑bed boost after breast‑conserving surgery for patients who achieve a complete response to neoadjuvant chemotherapy

A Multicenter, Single-arm Phase II Clinical Study on Exempting Tumor Bed Boost Radiotherapy for Patients Achieving pCR After Breast Conserving Surgery With Neoadjuvant Therapy

This study will try skipping the extra 'boost' radiation to the tumor bed in people with breast cancer who achieve a pathologic complete response after neoadjuvant chemotherapy and breast‑conserving surgery to see if it's safe and lowers treatment side effects.

Quick facts

• Phase: Phase 2
• Study type: Interventional
• Enrollment: 150 (estimated)
• Ages: 30 Years to 75 Years
• Sex: Female
• Sponsor: The First Affiliated Hospital with Nanjing Medical University (Academic / other)
• Drugs / interventions: chemotherapy
• Locations: 1 site (Nanjing, Jiangsu)
• Trial ID: NCT07113613 on ClinicalTrials.gov

What this trial studies

This is a prospective, single‑arm, phase II study enrolling patients with invasive breast cancer who achieve a pathologic complete response (ypT0) after guideline‑based neoadjuvant chemotherapy and breast‑conserving surgery. Enrolled patients will not receive additional dose escalation (a tumor‑bed boost) to the surgical site and will be followed for local‑regional recurrence, survival outcomes, and treatment‑related toxicity. The trial aims to identify the subgroup of patients for whom the boost can be safely omitted and to inform more precise adjuvant radiotherapy planning. It is described as the first prospective single‑arm effort focused specifically on omission of tumor‑bed boost in the pCR population.

Who should consider this trial

Good fit: Ideal candidates are people aged 30–75 with a single invasive breast lesion who received standard neoadjuvant chemotherapy, underwent breast‑conserving surgery with negative margins (≥1 mm), achieved ypT0 (pCR), have ECOG 0–1, adequate organ function, and no prior chest radiotherapy.

Not a fit: Patients who did not achieve pCR, have multifocal disease or positive/close margins, prior chest radiotherapy, significant organ dysfunction, or who are pregnant or breastfeeding are unlikely to benefit and are excluded.

Why it matters

Potential benefit: If successful, eligible patients could avoid the extra tumor‑bed boost, reducing radiation side effects and preserving normal tissue without raising recurrence risk.

How similar studies have performed: Retrospective and observational studies show lower local recurrence after pCR supporting de‑escalation strategies, but prospective randomized evidence specifically omitting the tumor‑bed boost is limited, so this approach remains relatively novel.

Eligibility criteria

Inclusion Criteria:

(1) Voluntary participation, good compliance, able to cooperate with the trial observation, and having signed a written informed consent form; (2) Confirmed as invasive cancer through pathological tissue examination, and received baseline breast MR or PET/MR examination before neoadjuvant therapy; (3) Received the standard neoadjuvant treatment plan recommended by the guidelines based on molecular typing; (4) Single lesion, initially diagnosed as cT1-3N0-3a; (5) Underwent breast-conserving surgery, with negative surgical margins and a margin distance of ≥1mm, and achieved pCR of the primary breast lesion after NAC (ypT0); (6) Age 30-75 years, ECOG score 0-1; (7) Met the basic requirements for adjuvant radiotherapy, including basically normal peripheral blood count, no significant abnormalities in heart, liver, and kidney functions, and basically normal electrocardiogram; (8) Had no previous chest radiotherapy.

Exclusion Criteria:

(1) Pregnant women, lactating women, or women with reproductive capacity but without contraceptive measures in place; (2) Known to carry mutated susceptibility genes for breast cancer (including BRCA-1 and BRCA-2); (3) Diagnosed with cT4, N3b-c, bilateral breast cancer, with multiple primary lesions, multicentricity or non-bulky enhancement at the primary site; (4) Not receiving the standard neoadjuvant treatment regimen recommended by guidelines, or the primary breast lesion did not achieve pCR (including ypTis) after NAC; (5) Suffering from other malignant tumors or participating in other clinical trials simultaneously; (6) Unable to start radiotherapy within 8 weeks after breast cancer surgery; (7) Diagnosed with distant metastasis through initial imaging or pathology; (8) Previous history of breast cancer, history of radiotherapy in the neck, chest or ipsilateral axilla; (9) Severe non-tumor-related medical comorbidities affecting the implementation of radiotherapy; (10) Suffering from uncontrollable neurological, mental disorders or mental impairments, with poor compliance and inability to cooperate and describe treatment responses.

Where this trial is running

Nanjing, Jiangsu

• The First Affiliated with Nanjing Medical University (Jiangsu Province People's Hospital) — Nanjing, Jiangsu, China (Recruiting)

Study contacts

• Principal investigator: Xinchen Sun, Doctor — The First Affiliated with Nanjing Medical University (Jiangsu Province People's Hospital)
• Study coordinator: Xinchen Sun, Doctor

Conditions Breast Cancer; Radiotherapy; Exemption of tumor bed dosage increase; Breast-conserving treatment; Neoadjuvant chemotherapy