Clinical trial Recruiting at 9 sites Phase 2 Interventional Ages 50 and up Women only

Proton therapy for early stage breast cancer treatment

Official title: Phase II Protocol of Proton Therapy for Partial Breast Irradiation in Early Stage Breast Cancer

Run by Proton Collaborative Group · NCT01766297 · Data updated 2026-11-12

This study is testing whether proton therapy can be a better treatment for women with early stage breast cancer by focusing on the tumor while reducing side effects compared to traditional radiation.

More Breast Cancer trials

Quick facts

PhasePhase 2
Study typeInterventional
Ages50 Years and up
SexWomen only
Enrollment132 (estimated)
SponsorProton Collaborative Group
Research network
Drugs / interventionschemotherapy, radiation
Locations9 sites (Scottsdale, Arizona and 8 other locations)
StatusRecruiting
StartedFebruary 2013
Main results expectedJanuary 2027
Study endsJanuary 2035
Registry record updatedSeptember 29, 2026
Trial IDNCT01766297 on ClinicalTrials.gov

Is this trial a fit for you?

Likely a good fit

Ideal candidates for this study are women over 50 years old with early stage invasive ductal carcinoma or ductal carcinoma in situ.

Probably not a fit

Patients with lobular carcinoma or those who do not meet the specific tumor size and stage criteria may not benefit from this study.

A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.

What this trial studies

This clinical trial aims to evaluate the effects of proton radiation therapy on women with early stage breast cancer. The study compares the outcomes of proton therapy to traditional whole breast irradiation, focusing on the potential benefits of targeting only the tumor site. By limiting radiation exposure to surrounding healthy tissue, the trial seeks to reduce side effects and improve patient convenience and cost-effectiveness. Participants will receive proton therapy as a part of their treatment regimen, and the study will assess both the positive and negative impacts of this approach.

Why it matters

Potential benefit: If successful, this treatment could offer a safer and more effective option for women with early stage breast cancer.

How similar studies have gone: While there is limited clinical data on proton therapy for partial breast irradiation, other studies have shown promise in using proton therapy for various cancers.

Who can join: the full rules

Show full inclusion / exclusion criteria
Inclusion Criteria:

* Must sign study-specific, IRB approved informed consent form prior to study entry. Note consent by legally authorized representative is not allowed for this trial.
* Must be female.
* Must be \> = 50 years of age.
* Must have a life expectancy of at least 5 years based on age and co-morbidities.
* Must have pathology proven invasive ductal carcinoma (lobular is not allowed) and/or ductal carcinoma in situ (DCIS).
* One of the following criteria must be met: (a) Tumors that are microscopically multifocal must be 3.0 cm or less in total aggregate size and encompassed within a single scar (b) Patient does not have microscopically multifocal tumor.
* For tumors that are invasive, if in the presence of extensive intraductal component (EIC), the entire pathologic tumor size (including both the intraductal and invasive component) must be 3.0 cm or less.
* Must be Stage 0, I, II (Tis, T1, or T2, N0, M0 per AJCC criteria 7th and/or 8th Ed.). If stage II, the tumor size must be \< = 3.0 cm. A patient with invasive histology must have nodal stage pN0 by H\&E stains on sentinel node biopsy or axillary lymph node dissection.
* Must have ER positive disease with ER/PR report available.
* For tumors that are invasive, HER2 must be performed (positive or negative is acceptable).
* Must have a lumpectomy performed, with documented negative surgical margins by 0.2 cm or more. If re-excision results in negative surgical margins 0.2 cm or more, patient is eligible.
* If image guidance with daily cone beam CT with direct physician visual assessment is used for treatment positioning, the presence of markers or clips in the surgical bed is recommended but not required. If cone beam CT imaging will NOT be used for image guidance, then the patient must be prepared to have 2 fiducial markers minimum, 3 preferred, placed prior to treatment (if not previously done).

  * If markers or clips were placed at the time of surgery, patient must be able to start treatment within 12 weeks after lumpectomy or re-excision for adequate margins.
  * If markers were not placed at the time of surgery and are needed, patient must have markers placed within 6 weeks after surgery.
  * If systemic chemotherapy was given, patient must have had clips or markers placed at the time of surgery (if they are needed) and patient must have simulation scans within 6 weeks of the completion of the chemotherapy.
* Must be able to start treatment within 12 weeks of surgery or 8 weeks of finalization of chemotherapy.

Exclusion Criteria:

* Previous history of ipsilateral invasive breast cancer or DCIS.
* Any clinical or radiographically suspicious nodes, unless biopsy proven benign.
* Non-epithelial malignancies such as sarcoma or lymphoma.
* Suspicious residual microcalcifications on mammography of either breast, unless negative for malignancy on pathology.
* Multicentric or bilateral disease unless biopsy of the clinical abnormalities are performed and result is negative.
* Lymphovascular space invasion (LVSI) on pathology specimen.
* Any previously treated breast carcinoma or synchronous breast carcinoma in ipsilateral breast.
* Prior radiation therapy to the ipsilateral breast or thorax.
* Paget's disease of the nipple.
* Histologic examination showing invasive lobular histology.
* Skin involvement.
* Breasts technically unsatisfactory for radiation treatment upon the discretion of the treating physician.
* Significant infection or other co-existing medical condition that would preclude protocol therapy such as pregnancy, HIV/AIDS or collagen vascular diseases specifically systemic lupus erythematosus, scleroderma, or dermatomyositis.
* Known BRCA 1 or BRCA 2 mutation.
* Pregnant or lactating.

Where it's running

  • Mayo Clinic
    Scottsdale, Arizona, United States
    Recruiting
  • California Protons Cancer Therapy Center
    San Diego, California, United States
    Recruiting
  • Northwestern Medicine Chicago Proton Center
    Warrenville, Illinois, United States
    Recruiting
  • Maryland Proton Treatment Center
    Baltimore, Maryland, United States
    Recruiting
  • McLaren Proton Therapy Center
    Flint, Michigan, United States
    Recruiting
  • New York Proton Center
    New York, New York, United States
    Recruiting
Show 3 more locations
  • Oklahoma Proton Center
    Oklahoma City, Oklahoma, United States
    Recruiting
  • Inova Schar Cancer Institute
    Fairfax, Virginia, United States
    Recruiting
  • Hampton University Proton Therapy Institute
    Hampton, Virginia, United States
    Recruiting

Similar studies

Other studies for the same condition or treatment. Recruiting studies are listed first.

How to take part

  1. Review the eligibility criteria above with your treating physician.
  2. Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
  3. Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.
Last reviewed 2026-11-14 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.