2025 Poster Presentations
P097: CARRE, CARBON RADIOTHERAPY FOR RARE TUMORS: ELECTRONIC CONSENT AND FOLLOW-UP
Adam Holtzman1; Aimée Galatas, BS2; Homan Mohammadi1; Jeffrey Janus1; Samip Patel1; Yujie Zhao1; Angela Donaldson1; Osarenoma Olomu1; Joao Paulo Cavalcante de Almeida1; Emily Liu1; Lauren Haydu1; Bradford Hoppe1; 1Mayo Clinic Florida; 2Louisiana State University School of Medicine
Introduction: We propose a novel study design to address a critical gap in the treatment of unresectable adenoid cystic carcinoma (ACC) of the head and neck (H&N), a rare tumor with limited research and poor patient outcomes. Prospective clinical studies for such rare tumors are difficult to conduct due to significant costs and challenges in enrolling sufficient patient numbers. Consequently, outcomes for affected patients remain poor, with current treatments using photon/proton radiation achieving suboptimal local control rates of 50-60% at three years, with local recurrences being the primary cause of mortality. High Linear Energy Transfer (LET) radiation, such as fast neutron therapy, has shown improved efficacy but poses significant toxicity risks. Carbon ion radiotherapy (CIRT), a high LET radiation with better conformality, has emerged as a preferred treatment option in Europe and Asia, achieving 2-year local control rates of 80-90% and is recognized by NCCN guidelines as appropriate for unresectable ACC. Mayo Clinic Florida (MCF) is pioneering the establishment of the first CIRT center in North America, expected to begin treating patients in 2028. However, North American patients currently lack access to this treatment modality.
Methods: To address this gap, we propose a prospective two-arm clinical trial to investigate the benefits of a CIRT boost combined with standard photon/proton radiation for patients with unresectable ACC of the H&N. This study will leverage novel clinical trial infrastructure designed to minimize costs and personnel requirements, enabling virtual enrollment and treatment. Patients will be referred from partnering high-volume head and neck institutions and consented through a virtual video consent process through MCF. Group 1 will receive an upfront boost of CIRT of up to 8 treatments (24GyE at 3GyE), followed by 25-30 treatments of photon/proton therapy (45-50GyRBE) at their partner institution. For those unable to travel, enrollment in a prospective registry component (Group 2) will be offered. Secondary endpoints include patient quality of life, patient-reported outcomes, progression-free survival, and overall survival.
The study will be powered to detect a difference in the primary endpoint, the two-year local control (LC) rate, between patients treated with and without CIRT. Local disease progression will be assessed using clinical or radiographic exams as per RECIST 1.1 criteria. Based on literature estimates, the two-year LC for patients treated with photon/proton radiation is expected to be 50%, compared to 90% for those treated with the combination of CIRT and photon/proton radiation. With a two-sided alpha of 0.05 and desired power of 80%, 14 participants will be required in each group, totaling 28 patients.
Conclusion: This study aims to transform the therapeutic landscape for rare tumors by generating North American-based evidence for the efficacy and safety of CIRT and providing a platform for multinational, multi-institutional trials. This may not only pave the way for broader access to CIRT research in the United States but also increase study accrual for patients with other rare tumors beyond those with ACC if successful.
