The Oligopro-Breast trial is a Phase II study targeting women with ER+/HER2- metastatic breast cancer who have been on endocrine therapy and/or CDK4/6 inhibitors for at least 6 months, and show progressive disease at 1-3 extracranial metastases, which are treatable locally. The trial aims to investigate if treating these resistant metastases with SBRT (or other local treatments if SBRT is not possible) can extend the use of the current systemic therapy.
Patients will continue their existing systemic treatment while receiving SBRT on all progressive lesions. If new oligoprogression occurs, SBRT will be performed again. A new systemic treatment line will start if there is polyprogression (more than 3 lesions at once), progression of more than 6 lesions over 12 months, intracranial progression, or lesions that cannot be treated locally.
The scientific question is whether local treatment of resistant metastases can prolong the effectiveness of ongoing systemic therapy, which is particularly beneficial if the treatment is well-tolerated. The primary objective is to measure the proportion of patients surviving without changing their systemic treatment line at 6 months after SBRT.
This trial is significant for patients as it explores a method to potentially extend the duration of effective and well-tolerated treatments, offering hope for better management of metastatic breast cancer.
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.
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.
Single group
SBRT
RadiationSBRT of all oligoprogressive metastases (or other local therapy if SBRT not advisable), followed by continuation of the same systemic therapy.
NExt Systemic Treatment-Free Survival (NEST-FS)
Time to next line of systemic therapy (NEST)
Progression-free survival (PFS)
Modified Progression-free survival (mPFS)
Defined as the survival in the absence of any of the following : (1) polyprogression (progressive disease of more than 3 lesions at the same time), (2) progression of more than 6 lesions over a 12-month rolling period, (3) intracranial progression, (4) progressing lesion that cannot be treated locally, or (5) death.
Chemotherapy-free survival
Correlation between (1) ctDNA burden at baseline and (2) ctDNA burden 10-12 weeks after SBRT versus the modified progression-free-survival (mPFS). NEST-FS in function of ESR1 status.
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