Stereotactic radiotherapy for limited progression in ER+/HER2- metastatic breast cancer

The Oligopro-Breast Study: Stereotactic Radiotherapy for Oligoprogressive ER+/HER- Metastatic Breast Cancer, a Prospective Phase 2 Study

This trial will try stereotactic body radiotherapy (SBRT) to treat 1–3 new resistant extracranial metastases in women with ER+/HER2- metastatic breast cancer on endocrine therapy and/or CDK4/6 inhibitors to see if local treatment lets them stay on their current systemic therapy longer.

Quick facts

• Phase: Not applicable
• Study type: Interventional
• Enrollment: 48 (estimated)
• Ages: 18 Years and up
• Sex: Female
• Sponsor: Jules Bordet Institute (Academic / other)
• Drugs / interventions: radiation
• Locations: 5 sites (Brussels and 4 other locations)
• Trial ID: NCT06925984 on ClinicalTrials.gov

What this trial studies

This prospective Phase II trial enrolls women with ER+/HER2- metastatic breast cancer who have been on endocrine therapy and/or CDK4/6 inhibitors for at least six months and now have progression at 1–3 extracranial sites. Eligible progressive lesions will receive stereotactic body radiotherapy (SBRT) or another local ablative treatment if SBRT is not feasible, while patients remain on their current systemic therapy. The protocol allows repeat local treatment for new oligoprogression; a switch to a new systemic line is triggered by intracranial progression, polyprogression (>3 lesions at once), more than six progressing lesions within 12 months, or lesions not amenable to local therapy. The trial aims to determine whether controlling a few resistant metastases locally can prolong the benefit of ongoing endocrine/CDK4/6 therapy.

Who should consider this trial

Good fit: Women with histologically confirmed ER+/HER2- metastatic breast cancer on first- or second-line endocrine therapy with or without CDK4/6 inhibitors for at least six months, ECOG 0–2, who have 1–3 extracranial progressive lesions that are amenable to local treatment are ideal candidates.

Not a fit: Patients with polyprogression (>3 new lesions), progressive or newly diagnosed brain metastases, lesions that cannot be treated locally, prior local treatment of the same progressing lesion under the current systemic line, or an active second malignancy are unlikely to benefit from this approach.

Why it matters

Potential benefit: If successful, this approach could let patients remain on an effective endocrine/CDK4/6 regimen longer by controlling a few resistant lesions locally and delaying the need to change systemic treatment.

How similar studies have performed: Similar SBRT approaches for limited metastatic progression have shown promising results in other cancers and in small series for breast cancer, but high-quality randomized evidence specifically in ER+/HER2- patients on CDK4/6 inhibitors remains limited.

Eligibility criteria

Inclusion Criteria:

* ECOG performance status 0-2.
* Histologically confirmed ER+/HER2- MBC.
* History of polymetastatic disease. Patients with genuine oligometastatic disease and 1-3 oligoprogressive lesions are only allowed if ablative therapy of all metastases is deemed impossible.
* Under 1st to 2nd systemic treatment line with hormonotherapy and/or CDK4/6 inhibitors for at least 6 months before progression.
* Progressive disease at 1-3 extracranial sites.
* Ability to treat all progressive lesions locally according to the treating radiation oncologist.

Exclusion Criteria:

* Second malignancy if it is not in complete remission.
* Previous local treatment for oligoprogression under the current systemic treatment line
* Current progression in a lesion that has been treated with SBRT before and is not amendable for surgery or radiofrequency ablation (RFA).
* Progressive or newly diagnosed brain metastases. Known brain metastases that have been nonprogressive for at least 6 months, are not an exclusion criterion.
* Inability to continue the same ST line after local therapy (for example because of toxicity or patient refusal).
* Pregnancy.
* Inability to sign the informed consent.

Where this trial is running

Brussels and 4 other locations

• Jules Bordet Institute — Brussels, Belgium (Recruiting)
• UZ Gent — Ghent, Belgium (Recruiting)
• AZ Groeninge — Kortrijk, Belgium (Recruiting)
• AZ Sint-Maarten — Mechelen, Belgium (Recruiting)
• CHU UCL Namur - Site Saint Elisabeth — Namur, Belgium (Recruiting)

Study contacts

• Study coordinator: Robbe Van den Begin, MD PhD

Conditions OligoProgressive Metastatic Disease; Oligoprogression; metastatic breast cancer; CDK4/6 inhibitors; SBRT; SABR; radiotherapy