ESTRO 2024 - Abstract Book

S1911

Clinical - Mixed sites, palliation

ESTRO 2024

Radiation Oncology, Meldola, Italy. 9 Rabin Medical Center, Medical Physics, Petach Tiqva, Israel. 10 West Cancer Center, Medical Physics, Germantown, USA. 11 Memorial Sloan Kettering Cancer Center, Medical Physics, New York, USA. 12 Rambam Medical Center, Head and Neck Surgery Unit, Haifa, Israel. 13 Alpha Tau Medical, Clinical Department, Jerusalem, Israel. 14 Memorial Sloan Kettering Cancer Center, Radiation Oncology, New York, USA. 15 Rambam Medical Center, Oncology, Haifa, Israel. 16 Hadassah Medical Center, Otolaryngology, Jerusalem, Israel

Purpose/Objective:

To report the long-term toxicity and tumor control outcomes for patients with unresectable, recurrent, or locally advanced head and neck or skin tumors treated with a novel Radium-224 alpha-emitting radionuclide therapy (Alpha DaRT) across four prospective trials at several international institutions.

Material/Methods:

Between February 2017 and December 2022, 81 lesions in 71 patients were treated with Radium-224 Alpha DaRT therapy in prospective trials whose objective was to assess early toxicity and tumor response outcomes. Eligibility criteria for these studies included those with biopsy-proven recurrent or unresectable squamous cell or basal cell carcinoma of the skin or squamous cancer of the head and neck who either previously failed or were medically unfit for definitive therapy. Treatment was delivered via a percutaneous interstitial technique with placement of the Alpha DaRT to encompass the tumor volume with margin. Initial tumor response was assessed at a median of 10 weeks from the procedure. Acute toxicity was defined as complications which developed within 3 months from DaRT insertion and late toxicity was defined as complications which presented after this point in time. Toxicity was scored according to the Common Terminology Criteria for Adverse Events (CTCAE v5). Tumor control was assessed using serial radiographic imaging or clinical assessments.

Results:

The median follow up was 14 months (range: 2-51 months). A complete response (CR) was observed in 89% of treated lesions (n=72), 10% (n=8) demonstrated a partial response while one patient was not evaluable. The 2-year actuarial local recurrence-free survival (LRFS) was 77% [95% CI 63 – 87]. The 2-year disease-free survival among patients who exhibited an initial CR versus PR was 78% vs 43% (p=0.0015). Variables including recurrent vs non recurrent lesions, baseline tumor size, or histology did not impact upon long-term outcomes. Twenty percent of patients developed acute grade 2 or higher toxicity which subsequently resolved with conservative measures. There was no grade 2 or higher late toxicities observed in this cohort.

Conclusion:

The overwhelming majority of patients in this pooled cohort of patients treated on prospective international Alpha DaRT trials achieved a complete response which was associated with a 77% durable tumor control rate at 2 years. Long-term moderate or severe toxicities were not observed in this patient population.

Keywords: skin cancer, alpha-emitter radiation therapy