Breast Cancer InvasivePhase 2COSMONCT05301881
COntinue the SaMe Systemic Therapy After Local Ablative Therapy for Oligo Progression in Metastatic Breast Cancer - the COSMO Study
A Phase 2 study testing Surgery, Radiotherapy and Radiofrequent ablation in people with Breast Cancer Invasive and Metastatic Cancer, run by The Netherlands Cancer Institute at 7 sites in Netherlands.
Trial summary
Patients with oligoprogression of metastatic breast cancer during palliative treatment that is amenable to local therapy will be included. The local ablative therapy (LAT) may consist of stereotactic ablative radiotherapy (SABR), also known as stereotactic body radiation therapy, surgery or percutaneous ablation. Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Breast Cancer Invasive, Metastatic Cancer, Oligoprogressive
- What is being tested?
- Surgery, Radiotherapy and Radiofrequent ablation
- Type of treatment
- Surgery or procedure
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 56 participants
- Where
- 7 sitesNetherlands
- Study dates
- 17 Apr 2023to 1 Apr 2040
- Phase
- Phase 2
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Histologically confirmed invasive breast cancer
- Metastatic breast cancer
- o Oligoprogression is defined as an increase of ≥20% in size or, in case of FDG-PET-CT, metabolic activity (≥20% in SUVmax) involving a maximum of two lesions. These lesions may consist of: 1 or 2 distant metastatic lesions limited to 1 organ, the primary tumor or locoregional lymph nodes.
- Systemic treatment can be either endocrine, targeted, chemotherapy or immune-checkpoint blockade
- Patients should be on systemic therapy for at least six months. Status should be stable disease or partial or complete response for at least 6 months.
- Oligoprogression has to be detected with radiological imaging comparing the lesion on the same type of imaging modality as has been used at the start of systemic therapy.
Show all 14Show fewer
- Lesion(s) must be amenable to resection, radiotherapy or percutaneous ablation with the intent of local obliteration.
- The radiological imaging that shows progression must be performed within 70 days prior to LAT.
- Bone metastases are classified as progressive if the lytic component of the lesion increases by ≥20% or the FDG-uptake increases by ≥20% on FDG-PET-CT
- Lymph nodes should be larger than 15 mm upon first detection of oligoprogression to be classified as progressive.
- Oligo-progression has to be confirmed with a FDG-PET-CT-scan 5-7 weeks after the initial scan that showed oligoprogression.
- Age ≥18
- World Health Organization (WHO) Performance Status 0 or 1
- Signed written informed consent before patient registration according to ICH/GCP, and national/local regulations
Who cannot join
- Having received more than two lines of systemic therapy for MBC If a treatment regimen has been de-escalated without adding other therapies, this is seen as one line of therapy. For example: Pertuzumab/trastuzumab+docetaxel followed by pertuzumab/trastuzumab will be viewed as one line of systemic therapy.
- Other malignancy except carcinoma in situ and basal-cell and squamous cell carcinoma of the skin, unless the other malignancy was treated ≥5 years ago with curative intent without the use of chemotherapy or radiation therapy
- Current pregnancy or breastfeeding. Women of childbearing potential must use adequate contraceptive protection
- Presence of any medical condition that would place the patient at unusual risk, up to the discretion of the clinician
- Presence of any psychological, familial, sociological, or geographical condition potentially hampering compliance with the study protocol and follow-up schedule
Trial locations and contacts
7 sites in 1 country. Contact the study team or a site near you to ask about taking part.
Robin van den Borg, MD contact
7 sites in 1 country
Netherlands7 sites, 7 recruiting
- Recruiting
Noordwest Ziekenhuisgroep
Alkmaar
S Vrijaldenhoven, MD
S Vrijaldenhoven, MD
- Recruiting
Antoni van Leeuwenhoek
Amsterdam
G Sonke, MD, g.sonke@nki.nl
Robin van den Borg, MD, r.vd.borg@nki.nl
- Recruiting
Rijnstate
Arnhem
K J Beelen, MD, +31880058888, info@rijnstate.nl
K J Beelen, MD
- Recruiting
Deventer ziekenhuis
Deventer
LW. Kessels, MD
A Imholz, MD
- Recruiting
ADRZ
Goes
E van Vliet, MD, +31881250000, researchbureau@adrz.nl
E van Vliet, MD
- Recruiting
Martini ziekenhuis
Groningen
A van der Velden, MD
A van der Velden, MD
- Recruiting
Antonius ziekenhuis
Utrecht
M Agterof, MD
M Agterof, MD
About this study
Patients with oligoprogression of metastatic breast cancer during palliative treatment that is amenable to local therapy will be included. The local ablative therapy (LAT) may consist of stereotactic ablative radiotherapy (SABR), also known as stereotactic body radiation therapy, surgery or percutaneous ablation.
- Conditions
- Breast Cancer Invasive, Metastatic Cancer, Oligoprogressive
- Being tested
- Surgery, Radiotherapy, Radiofrequent ablation
- Medical subject headings
- Neoplasm Metastasis
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
SurgeryProcedure or surgery
resection of the oligometastatic lesion(s)
RadiotherapyRadiation
radiation of the oligometastatic lesion(s)
Radiofrequent ablationOther
radiofrequent ablation of the oligometastatic lesion(s)
| Study group | Role | What they receive |
|---|---|---|
| Surgery, radiotherapy or radiofrequent ablation | Other | The oligoprogresive lesion(s) will be treated with Surgery, radiotherapy or percutaneous ablation depending on the location of the lesion. treatment will be standard of care and will be decided by the treating team of the patient. Receives: Procedure: Surgery; Radiation: Radiotherapy; Other: Radiofrequent ablation |
What is being measured
The primary outcome is the main question the study is designed to answer.
Number of patients free of progression at 6 months
progression-free survival at 6 months (PFS-6)
Measured: At 6 months
Secondary outcomes (7)
Number of patients free of progression at 6 months per histoligical subtype
PFS-6 for breast cancer subtypes: ER+/HER2- vs. HER2+ vs. TN
Measured: At 6 months
Number of patients free of progression at 6 months per breast cancer subtype
PFS-6, stratified by breast cancer subtype
- localization of progressive lesion
Measured: At 6 months
Number of patients free of progression at 6 months per localization of progressive lesion
PFS at 6 months separately for localization of progressive lesion: locoregional vs. cranial vs. visceral vs. bone
Measured: At 6 months
Overall Surival (OS)
Evaluation of overall survival measured from baseline till death due to any cause
Measured: Up to 120 months
Time to next line of treatment
Time to next line of systemic therapy meeasured from baseline
Measured: Up to 120 months
Number of patients who develop "visceral crisis"
number of patients who develop "visceral crisis"
Measured: Up to 120 months
Number of patients who develop complications after local ablative treatment
Assess the number of patients who develop complications after local ablative treatment
Measured: Up to 120 months
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted31 Mar 2022
- Study start17 Apr 2023
- Primary completion1 Apr 2035 (estimated)
- Study completion1 Apr 2040 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Breast Cancer InvasiveStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 2
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Model description
- Lesion(s) will be treated with surgery, radiotherapy or radiofrequent ablation depending on the location. The treatment is standard of care and will be decided in the treating team of the patient.
- Masking
- None (open label)
- Enrolment
- 56 participants (estimated)
Sponsor and investigators
- Lead sponsor
- The Netherlands Cancer Institute
- Sponsor type
- University, hospital or other
- Collaborators
- Maarten van de Weijden Foundation
- Responsible party
- Sponsor
- Investigators
- G Sonke, Principal investigator, The Netherlands Cancer Institute
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05301881
- Sponsor's protocol ID
- M21CSM
- Acronym
- COSMO
- Status last verified
- Sep 2026
- First submitted
- 21 Mar 2022
- Last updated
- 11 Sep 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided: to be determined
Study at a glance
From the registry record, last updated by the sponsor on 11 Sep 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- COntinue the SaMe Systemic Therapy After Local Ablative Therapy for Oligo Progression in Metastatic Breast Cancer - the COSMO Study
- ClinicalTrials.gov ID
- NCT05301881
- Acronym / sponsor ID
- COSMO / M21CSM
- Conditions
- Breast Cancer Invasive, Metastatic Cancer, Oligoprogressive
- Phase
- Phase 2
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 56 participants (estimated)
- Lead sponsor
- The Netherlands Cancer InstituteUniversity, hospital or other
- Collaborators
- Maarten van de Weijden Foundation
- Study start
- 17 Apr 2023 (actual)
- Primary completion
- 1 Apr 2035 (estimated)
- Study completion
- 1 Apr 2040 (estimated)
- First posted
- 31 Mar 2022 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Patients with oligoprogression of metastatic breast cancer during palliative treatment that is amenable to local therapy will be included. The local ablative therapy (LAT) may consist of stereotactic ablative radiotherapy (SABR), also known as stereotactic body radiation therapy, surgery or percutaneous ablation.
Study design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
- Model description
- Lesion(s) will be treated with surgery, radiotherapy or radiofrequent ablation depending on the location. The treatment is standard of care and will be decided in the treating team of the patient.
| Arm | Type | Receives |
|---|---|---|
| Surgery, radiotherapy or radiofrequent ablation | Other | Procedure: Surgery, Radiation: Radiotherapy, Other: Radiofrequent ablationThe oligoprogresive lesion(s) will be treated with Surgery, radiotherapy or percutaneous ablation depending on the location of the lesion. treatment will be standard of care and will be decided by the treating team of the patient. |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (14 listed)
- Histologically confirmed invasive breast cancer
- Metastatic breast cancer
- o Oligoprogression is defined as an increase of ≥20% in size or, in case of FDG-PET-CT, metabolic activity (≥20% in SUVmax) involving a maximum of two lesions. These lesions may consist of: 1 or 2 distant metastatic lesions limited to 1 organ, the primary tumor or locoregional lymph nodes.
- Systemic treatment can be either endocrine, targeted, chemotherapy or immune-checkpoint blockade
- Patients should be on systemic therapy for at least six months. Status should be stable disease or partial or complete response for at least 6 months.
Key exclusion criteria (5 listed)
- Having received more than two lines of systemic therapy for MBC If a treatment regimen has been de-escalated without adding other therapies, this is seen as one line of therapy. For example: Pertuzumab/trastuzumab+docetaxel followed by pertuzumab/trastuzumab will be viewed as one line of systemic therapy.
- Other malignancy except carcinoma in situ and basal-cell and squamous cell carcinoma of the skin, unless the other malignancy was treated ≥5 years ago with curative intent without the use of chemotherapy or radiation therapy
- Current pregnancy or breastfeeding. Women of childbearing potential must use adequate contraceptive protection
- Presence of any medical condition that would place the patient at unusual risk, up to the discretion of the clinician
- Presence of any psychological, familial, sociological, or geographical condition potentially hampering compliance with the study protocol and follow-up schedule
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Surgeryresection of the oligometastatic lesion(s) | Procedure or surgery | Surgery, radiotherapy or radiofrequent ablation |
| Radiotherapyradiation of the oligometastatic lesion(s) | Radiation | Surgery, radiotherapy or radiofrequent ablation |
| Radiofrequent ablationradiofrequent ablation of the oligometastatic lesion(s) | Other | Surgery, radiotherapy or radiofrequent ablation |
Primary outcome
Number of patients free of progression at 6 months
Time frame: At 6 months
progression-free survival at 6 months (PFS-6)
7 secondary outcomes
Number of patients free of progression at 6 months per histoligical subtype
Time frame: At 6 months
Number of patients free of progression at 6 months per breast cancer subtype
Time frame: At 6 months
Number of patients free of progression at 6 months per localization of progressive lesion
Time frame: At 6 months
Overall Surival (OS)
Time frame: Up to 120 months
Time to next line of treatment
Time frame: Up to 120 months
Number of patients who develop "visceral crisis"
Time frame: Up to 120 months
Number of patients who develop complications after local ablative treatment
Time frame: Up to 120 months
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 11 Sep 2026.
- Individual participant dataSharing planned: Undecided. to be determined
Related trials for Breast Cancer Invasive
Active, not recruitingPhase 3
Tamoxifen Citrate, Letrozole, Anastrozole, or Exemestane With or Without Chemotherapy in Treating Patients With Invasive RxPONDER Breast Cancer
Breast Ductal Carcinoma In Situ, Invasive Breast Carcinoma
Active, not recruitingPhase 3
Testing MK-3475 (Pembrolizumab) as Adjuvant Therapy for Triple Receptor-Negative Breast Cancer
Breast Carcinoma In Situ, Invasive Breast Carcinoma
Not yet recruitingPhase 2
Adding Preoperative Radiotherapy Based on Early Treatment Response in Breast Cancer
Invasive Breast Cancer
Active, not recruitingPhase 2
Cemiplimab in High-risk or Locally Advanced Luminal and Triple Negative Breast Cancer
Invasive Breast Cancer
RecruitingPhase 3
Metformin for the Treatment of Insulin Resistance in Women With Stage I-III Breast Cancer Completing Chemotherapy
Anatomic Stage I Breast Cancer AJCC v8, Anatomic Stage II Breast Cancer AJCC v8
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Robin van den Borg, MD contact
G Sonke principal investigator
The Netherlands Cancer Institute
7 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 2 study testing Surgery, Radiotherapy and Radiofrequent ablation in people with Breast Cancer Invasive and Metastatic Cancer, run by The Netherlands Cancer Institute at 7 sites in Netherlands.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 14 inclusion and 5 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 11 Sep 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 7 sites in Netherlands. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact G Sonke, MD (+31-20-512 ext. 9111, g.sonke@nki.nl), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Number of patients free of progression at 6 months (time frame: At 6 months). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 11 Sep 2026.