OCTOPUS Trial Aims to Speed Access to Rare Sarcoma Drugs

A single master protocol is now grouping multiple experimental drug studies for rare pediatric, adolescent, and young adult sarcomas under a single shared infrastructure. The approach is designed to overcome the trial-recruitment barriers that have long stalled drug development for these ultra-rare cancers, according to an editorial published in Tumori Journal.¹

The platform, called OCTOPUS (Optimising Combination Therapy fOr Paediatric, adolescent and yoUng adult patients with non-rhabdomyosarcoma soft tissue Sarcomas), targets non-rhabdomyosarcoma soft tissue sarcomas (NRSTS), which is a group of more than 50 distinct tumor subtypes that together make up roughly 4% to 5% of childhood cancers.

NRSTS were once managed as a single, broad disease category with a uniform treatment approach, but care is now moving toward therapy tailored to specific histologic subtypes and, in some cases, to molecular subgroups.

“Implementation of these treatments is nevertheless clearly limited by the extreme rarity of each individual histotype,” the authors wrote. “Due to the low numbers, conducting clinical trials for NRSTS has been difficult, and integrated international programmes are crucial.”

Rarity of NRSTS Subtypes Has Stalled Clinical Trial Progress

Two prior international studies, the European Paediatric Soft tissue sarcoma Study Group (EpSSG) NRSTS 2005 trial and the Children's Oncology Group's ARST0332 trial, established the current risk-adapted standards of care for NRSTS. But those standards leave real gaps: survival rates remain poor for high-risk disease, and no standard of care exists once a tumor becomes metastatic, progresses, or returns. Some histotypes, such as desmoplastic small round cell tumor (DSRCT) and malignant rhabdoid tumor, are intrinsically resistant to chemotherapy or develop resistance quickly.

There is a broader push to close diagnostic and treatment gaps in pediatric STS, including new National Comprehensive Cancer Network guidelines emphasizing risk stratification and trial enrollment,² and a nationwide liquid biopsy initiative in Poland aimed at sharpening molecular diagnosis for these same rare tumors.³ The OCTOPUS platform extends that trend by building a single legal and operational structure through shared case report forms, a translational research pipeline, and a network of coordinating centers across the EpSSG and Innovative Therapies for Children and Adolescents with Cancer consortium.¹ Through this platform, individual subtrials for specific histotypes or molecular subgroups can open faster and share infrastructure.

How Does the Platform Structure Work?

Rather than a single trial design, OCTOPUS functions as an umbrella: each subtrial is tailored to a specific patient population, disease biology, and stage of drug development and can be positioned in frontline or relapsed/refractory settings depending on medical need. Patients who aren't eligible for an open subtrial are instead tracked in a real-world data registry called SARC, which captures standard-of-care outcomes and can serve as a comparison population when patient numbers are too small to support randomized designs.

That registry function points to one of the platform's more consequential design choices for payers and health technology assessment (HTA) bodies. The editorial's authors note that HTA agencies have struggled to evaluate the cost-effectiveness of tumor-agnostic compounds because comparable standard-of-care data are hard to obtain for these small, heterogeneous "basket" populations. This follows a broader industry effort to build better real-world evidence frameworks to support tumor-agnostic therapy approvals, an area where regulators have flagged similar data gaps.⁴

The OCTOPUS team says it has already opened early discussions with the European Medicines Agency, the FDA, and HTA bodies to ensure the registry and subtrial data will be usable for registration and reimbursement decisions, not just for research purposes.¹

Three Histotypes Prioritized for Initial Subtrials

Three histotypes have been prioritized for initial subtrials: desmoid-type fibromatosis, extracranial malignant rhabdoid tumor, and DSRCT. The DSRCT subtrial, called WORTH, is a phase 1/2 dose-escalation study combining trabectedin and irinotecan in newly diagnosed patients; DSRCT carries a 5-year overall survival of just 10% to 20%, and treatment has historically been inconsistent across centers.

A second subtrial, SMARTY, will test adding gemcitabine to standard chemotherapy for tumors driven by SMARCB1 or SMARCA4 alterations—genetic changes linked to aggressive tumor growth—including malignant rhabdoid tumor and several related adult and pediatric cancers. Planned treatment approaches across the platform include targeted small-molecule inhibitors, immune checkpoint inhibitors, antibody–drug conjugates, and cellular therapies such as chimeric antigen receptor T cells and T-cell receptors.

Next Steps: Cross-Age Trials and Regulatory Alignment

The platform's designers are also pushing for cross-age collaboration, arguing that adolescents and young adults with sarcoma have historically fallen between pediatric and adult trial networks.⁵ Subtrials will be built around molecular targets and mechanism of action rather than strict age cutoffs, with age eligibility applied only where there's a specific biological or safety rationale, and adolescents will be supported for enrollment in adult phase 1/2 trials where appropriate. Patient and parent advocates hold seats on the platform's steering committee and on individual subtrial teams, with particular input into the patient-reported outcome measures being collected across the program.

International sponsorship for OCTOPUS and its subtrials is being coordinated by the Princess Máxima Center for Pediatric Oncology in the Netherlands, and the platform is linked to a companion molecular diagnostic study, MyKids, intended to feed preclinical findings back into trial design. Whether the model shortens the path to approved therapies for these ultra-rare cancers will depend in part on how regulators and payers ultimately treat the registry data the platform is built to generate.

“This multi-stakeholder initiative brings together academia, patient advocates, regulators and the pharmaceutical industry and will ultimately improve access to innovative therapies for patients with ultra-rare sarcomas,” the authors concluded.

References

1. Schoot RA, Casanova M, van Bindsbergen K, et al. Optimising combination therapy for paediatric, adolescent and young adult patients with non-rhabdomyosarcoma soft tissue sarcomas: the OCTOPUS platform trial. Tumori Journal. Published online July 30, 2026. doi:10.1177/03008916261456574
2. McCrear S. New pediatric soft tissue sarcoma guidelines emphasize risk stratification, clinical trials. AJMC. February 18, 2026. Accessed August 10, 2026. https://www.ajmc.com/view/new-pediatric-soft-tissue-sarcoma-guidelines-emphasize-risk-straitification-clinical-trials
3. McCrear S. Poland launches nationwide liquid biopsy program for pediatric STS care. AJMC. January 15, 2026. Accessed August 10, 2026. https://www.ajmc.com/view/poland-launches-nationwide-liquid-biopsy-program-for-pediatric-sts-care
4. Caffrey M. A better framework for developing RWD to support tumor-agnostic targeted therapies. Am J Manag Care. 2023;29(spec 5):SP428-SP430. https://www.ajmc.com/view/a-better-framework-for-developing-rwd-to-support-tumor-agnostic-targeted-therapies
5. Freyer DR. Seibel NL. The clinical trials gap for adolescents and young adults with cancer: recent progress and conceptual framework for continued research. Curr Pediatr Rep. 2015;3(2):137-145. doi:10.1007/s40124-015-0075-y