Radiotherapy Dose Escalation Failed to Improve Local Control for Intermediate-Risk Rhabdomyosarcoma on ARST1431: A Report from the Children's Oncology Group
Menée à partir des données d'un essai randomisé international de phase III incluant 297 patients atteints d'un rhabdomyosarcome à risque intermédiaire de récidive, cette étude analyse l'effet, sur le taux d'échec local à 3 ans, d'une augmentation de la dose de radiothérapie pour les patients présentant une tumeur de taille supérieure à 5 cm et une maladie résiduelle macroscopique au moment du traitement
PURPOSE: To evaluate local failure (LF) rates for patients with intermediate-risk rhabdomyosarcoma (IR-RMS) treated on the Children's Oncology Group (COG) ARST1431 clinical trial, the first and largest international, phase 3 randomized study to use FOXO1 fusion status for risk stratification. To improve local control, radiation therapy (RT) dose was increased to 59.4 Gy for patients with tumors >5cm and residual gross disease at the time of RT.
PATIENTS AND METHODS: For the 297 patients included, LF was defined as progression or relapse at the primary site. The rate of LF was calculated 3-years after enrollment.
RESULTS: LF for group III, FOXO1 fusion-positive patients (n=58) compared to fusion-negative patients (n=175) was 10.7% vs. 21.5%, respectively (p=0.08). The LF rate for patients with tumors >5cm at diagnosis (n = 180; 24.4%) was higher than that of patients with tumors ≤5cm at diagnosis (n = 117; 9.8%), p=0.002. The risk of LF for patients who received proton (n=99) vs. photon RT (n=126) was not different (16.1% vs. 15.9%, p=0.8). For the 75 patients with tumors >5cm at diagnosis and gross disease at the time of RT, the boost to 59.4 Gy did not improve the 3-year LF rate compared to that of patients who did not receive the boost (29.7% vs. 16.1%, p=0.6). For patients with group III/IV disease, those who underwent delayed primary excision (DPE) (n=72) had a lower LF rate compared to those who had RT alone (n=151) (5.8% vs. 19.7%, p<0.01).
CONCLUSION: On ARST1431, tumors >5cm at diagnosis had poor local control despite dose escalation to 59.4 Gy. Proton and photon RT had equivalent local control. For select patients, DPE significantly improved local control.
International Journal of Radiation Oncology, Biology, Physics , résumé, 2025