Open Trial: METTSEO for Newly Diagnosed & Widely Metastatic Ewing Sarcoma
XIT Review
Open Trial: METTSEO for Newly Diagnosed & Widely Metastatic Ewing Sarcoma
There is a new frontline strategy being tested for Ewing sarcoma patients with newly diagnosed & widely metastatic disease.
METTSEO takes inspiration from evolutionary biology and population dynamics. Instead of giving the tumor time to adapt to a predictable treatment pattern, the trial attempts to push cancer cells toward extinction through rapid, sequential changes in therapy.
The METTSEO trial — Metastatic Ewing’s Trial Testing Schedule Enhancement to Improve Outcomes — NCT07194044 is a Phase 1 study that opened in February 2026 and is sponsored by Moffitt Cancer Center.
The structure of this trial is a radical departure from standard oncology protocols.
Standard Ewing sarcoma treatment typically involves repeating the same alternating chemotherapy regimens over many months. The challenge with widely metastatic disease is that cancer cells may eventually learn how to survive those specific drugs through clonal evolution.
Here is how the protocol may be sequenced to help prevent resistance:
1. Initial First Strike: Weeks 1–8
Patients receive intensive induction therapy with vincristine, doxorubicin, and cyclophosphamide, also known as VDC.
This phase is designed to rapidly reduce the bulk of the cancer cell population.
2. Sequential Second Strikes: Weeks 9–38
Instead of simply repeating the first strike, the trial immediately shifts into 30 weeks of rapidly changing drug combinations.
This includes:
Irinotecan / Ifosfamide / Vincristine / Actinomycin D, also known as IrIVA
Cabozantinib with primary-site radiation
Topotecan / Cyclophosphamide
High-dose ifosfamide
Irinotecan / Temozolomide
The goal is to eliminate residual cancer cell populations by changing the therapeutic pressure before the cells have time to mutate, adapt, and become resistant.
3. Maintenance Chemotherapy: Weeks 39–104
This is followed by a prolonged maintenance phase using alternating 28-day blocks of chemotherapy:
Oral cyclophosphamide / etoposide
Alternating with vincristine / liposomal doxorubicin
The goal of this phase is to target any remaining dormant or resistant cancer cells and reduce the risk of relapse.
XIT Review Takeaway:
METTSEO is important because it challenges the traditional idea of repeating the same chemotherapy pattern over and over. Instead, it uses a rapid, sequential treatment strategy designed to stay ahead of tumor resistance.
For families facing newly diagnosed, widely metastatic Ewing sarcoma, this is a trial worth knowing about and asking their oncology team about.
Medical Disclaimer: The information provided by the XIT Foundation is for educational and informational purposes only and does not constitute professional medical advice, diagnosis, or treatment. The XIT Foundation does not endorse or recommend any specific commercial products, clinical trials, or treatments. Always seek the advice of a qualified physician or principal investigator with any questions you may have regarding a medical condition, treatment options, or trial eligibility.