An interventional study of Stereotactic Ablative Radiotherapy and Physician's choice of systemic treatment in Breast Cancer, Metastatic and Metastatic Breast Cancer, sponsored by Peter MacCallum Cancer Centre, Australia. Not yet recruiting. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-09-18.
Sponsored by Peter MacCallum Cancer Centre, Australia · Not applicable, Interventional, and Treatment
The goal of this clinical trial is to assess Stereotactic Ablative Radiotherapy (SABR) as a method to delay a change in systemic therapy in patients with oligoprogressive ER-positive, HER2-negative advanced breast cancer. The main question it aims to answer is to assess whether the addition of SABR to continuation of first line endocrine therapy and CDK 4/6 inhibitor (Arm A) to patients with oligoprogressive ER-positive, HER2-negative advanced breast cancer could have longer time to treatment failure (TTF) in comparison to physician choice of systemic treatment (Arm B) in patients who had progressed first line.
The treatment strategy in Arm A is to maintain patients on current endocrine therapy and CDK 4/6 inhibitor, controlling localised progressing sites of disease with SABR. Treatment strategy in Arm B is to maintain disease control with physician's choice of systemic therapy alone.
AVATAR II is a phase II multicentre open label, randomised trial. Following informed consent, eligible patients with ER-positive, HER2-negative advanced breast cancer receiving an ET (either AI or selective estrogen receptor degrader in combination with a CDK 4/6 inhibitor with newly diagnosed OPD amenable to SABR will be randomised to either:
Arm A: SABR to all known sites of OPD with continuation of first line therapy ET and CDK 4/6 inhibitor Arm B: Physician's choice of systemic treatment
Patients must have evidence of radiological response to ET and CDK 4/6 inhibitor for a minimum of six months prior to randomisation.
All patients will be followed up for 3 years after the last patient has been randomised.
14,825 studies on the registry are indexed under Breast Neoplasms; 3,319 are open to participants now.
This study's planned enrollment of 74 is close to the median of 72 across 10,896 interventional studies indexed under Breast Neoplasms.
Browse Breast Neoplasms studies →Peter MacCallum Cancer Centre, Australia is the lead sponsor of 82 studies on the registry; 25 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Patients will be eligible for inclusion in this trial if all the following criteria apply:
Patients must have evidence of radiological response to ET and CDK 4/6 inhibitor for a minimum of six months prior to randomisation.
Note: Patient must have ongoing stability/response in at least one lesion at the time of randomisation.
Evidence of new or existing OPD, as determined by the Investigator and defined according to RECIST1.1, via CT on a per-lesion basis (between 1-5 metastases, including the primary) as follows:
EXCLUSION CRITERIA
Patients will not be eligible for inclusion in this trial if any of the following criteria apply:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
HER2 is a protein, made from the ERBB2 gene, that drives the growth of some cancers. A study may look for a level of the protein, extra copies of the gene, or a particular change in it.
In breast cancer, protein tests are read as HER2-positive, HER2-low or HER2-negative; other cancers use their own rules. Check which test result the study requires.
A biopsy takes a small piece of tissue to examine. “Archival tissue” is a sample already taken, for example at diagnosis, and kept by the hospital.
Whether a stored sample will do depends on when it was taken, how much there is and what the study needs. Ask whether the study accepts your stored sample or needs a new biopsy.
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
A line of therapy is one course of treatment, which may combine several drugs. First-line is the first course given; second-line follows when that stops working or is not tolerated.
“Two prior lines” means two courses that count separately under the study’s rules — not simply two drugs. Ask the study team if you are unsure how yours are counted.
Cancer that has spread to the leptomeninges, the thin layers covering the brain and spinal cord, and the fluid between them. It is not the same as brain metastases.
Criteria often treat it separately, and many studies leave it out even where treated brain metastases are allowed.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Histologically or cytologically confirmed
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HER2
HER2 is a protein, made from the ERBB2 gene, that drives the growth of some cancers. A study may look for a level of the protein, extra copies of the gene, or a particular change in it.
In breast cancer, protein tests are read as HER2-positive, HER2-low or HER2-negative; other cancers use their own rules. Check which test result the study requires.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Biopsy and archival tissue
A biopsy takes a small piece of tissue to examine. “Archival tissue” is a sample already taken, for example at diagnosis, and kept by the hospital.
Whether a stored sample will do depends on when it was taken, how much there is and what the study needs. Ask whether the study accepts your stored sample or needs a new biopsy.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Metastases
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ECOG performance status
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Life expectancy
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Line of therapy
A line of therapy is one course of treatment, which may combine several drugs. First-line is the first course given; second-line follows when that stops working or is not tolerated.
“Two prior lines” means two courses that count separately under the study’s rules — not simply two drugs. Ask the study team if you are unsure how yours are counted.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Leptomeningeal disease
Cancer that has spread to the leptomeninges, the thin layers covering the brain and spinal cord, and the fluid between them. It is not the same as brain metastases.
Criteria often treat it separately, and many studies leave it out even where treated brain metastases are allowed.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
SABR to all known sites of oligoprogressive disease with continuation of first line therapy ET + CDK4/6i
Radiation: Stereotactic Ablative Radiotherapy
Physician's choice of systemic treatment does not mandate a change in systemic therapy, however, SABR is not permitted for management in this arm
Other: Physician's choice of systemic treatment
Stereotactic Ablative Radiotherapy
Physician's choice of systemic therapy does not mandate a change in systemic therapy, however, SABR is not permitted for management in this arm
Primary Outcome Measure
The primary endpoint of this study is to measure the time to treatment failure between Arm A and Arm B. Treatment failure is defined as time from randomisation to progression of disease resulting in a failure of treatment strategy or death by any cause. Progression, will be determined by the Investigator, using the Response Evaluation Criteria in Solid Tumors, Version 1.1. (RECIST1.1; Appendix 2) (33) as a guide. The treatment strategy in Arm A is to maintain patients on current ET and CDK 4/6 inhibitor, controlling localised progressing sites of disease with SABR. Treatment strategy in Arm B is to maintain disease control with physician's choice systemic therapy alone.
Time frame: Time from randomisation to progression of disease resulting in a failure of treatment strategy or death by any cause assessed until withdrawal of consent, death, or 3 years after the last patient has been randomised, whichever is earlier.
Secondary Objective 1
To compare PFS; PFS is assessed from randomisation to the date of the first evidence of progression or death by any cause. Progression will be assessed by the treating clinician as part of standard-of-care practice, using RECIST 1.1 as a guide or based on clinical progression.
Time frame: Time from randomisation to progression of disease resulting in a failure of treatment strategy or death by any cause assessed until withdrawal of consent, death, or 3 years after the last patient has been randomised, whichever is earlier.
Secondary Objective 2
To compare progression-free survival 2 (PFS-2); PFS-2 is assessed from randomisation to the date of progression on next line of systemic anti-cancer treatment or death by any cause.
Time frame: Time from randomisation to progression of disease resulting in a failure of treatment strategy or death by any cause assessed until withdrawal of consent, death, or 3 years after the last patient has been randomised, whichever is earlier.
Secondary Objective 3
To compare PFS of next line of treatment (2nd PFS); 2nd PFS is assessed from failure of treatment strategy to progression on next line of systemic anti-cancer treatment or date of death by any cause.
Time frame: Time from randomisation to progression of disease resulting in a failure of treatment strategy or death by any cause assessed until withdrawal of consent, death, or 3 years after the last patient has been randomised, whichever is earlier.
Secondary Objective 4
To compare OS; OS is assessed from randomisation to the date of death by any cause.
Time frame: Time from randomisation to progression of disease resulting in a failure of treatment strategy or death by any cause assessed until withdrawal of consent, death, or 3 years after the last patient has been randomised, whichever is earlier.
Secondary Objective 5
To compare treatment related adverse events (TRAEs); TRAEs are adverse events assessed using the Common Terminology for Adverse Events Version 5.0 (CTCAE v5.0) considered possibly, probably, or definitely related to treatment (systemic therapy or SABR)
Time frame: Time from randomisation to progression of disease resulting in a failure of treatment strategy or death by any cause assessed until withdrawal of consent, death, or 3 years after the last patient has been randomised, whichever is earlier.
Secondary Objective 6
To compare the QoL using the FACT-B total score: Area under the curve (AUC) of the FACT-B Total score from baseline to 48 weeks
Time frame: Time from randomisation to progression of disease resulting in a failure of treatment strategy or death by any cause assessed until withdrawal of consent, death, or 3 years after the last patient has been randomised, whichever is earlier.
No study locations are listed for this record.
Plan to share: No — Not contractually obliged but it may be considered
Start is estimated for Nov 2026; primary completion for Nov 2032, 72 months later.
Of 2,661 non-industry interventional studies with no phase under Breast Neoplasms, half reached primary completion within 33 months of starting (the median), counting those still running; a quarter within 16 and three quarters within 66. This study's planned 72 months is above that.
Counting every sponsor, half of 2,771 studies reached it within 33 months; a quarter within 15 and three quarters within 66.
How these figures are worked out, and which studies are left out of them.
This study is not yet recruiting, as verified in Sep 2026. You cannot join it, but the record below documents what was studied.
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Peter MacCallum Cancer Centre, Australia