Efficacy and safety of limited-margin conformal radiotherapy for pediatric rhabdomyosarcoma: long-term results of a phase II study.

Efficacy and safety of limited-margin conformal radiotherapy for pediatric rhabdomyosarcoma: long-term results of a phase II study.:

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Efficacy and safety of limited-margin conformal radiotherapy for pediatric rhabdomyosarcoma: long-term results of a phase II study.

Int J Radiat Oncol Biol Phys. 2020 Jan 24;:

Authors: Tinkle CL, Pappo A, Wu J, Hua CH, Shulkin BL, McCarville MB, Kaste SC, Davidoff AM, Bahrami A, Green DM, Ness KK, Merchant TE, Spunt SL, Krasin MJ

Abstract

BACKGROUND: To assess disease outcomes and late toxicities in pediatric patients with rhabdomyosarcoma treated with conformal photon radiation therapy (RT).

METHODS AND MATERIALS: Sixty-eight patients (median age, 6.9 years) were treated with conformal photon RT to the primary site on a prospective clinical trial. Target volumes included a 1-cm expansion encompassing microscopic disease. Prescribed doses were 36 Gy to this volume and 50.4 Gy to gross residual disease. Chemotherapy consisted of vincristine/dactinomycin (n=6); vincristine/dactinomycin/cyclophosphamide (VAC) (n=37); or VAC-based combinations (n=25). Patients were evaluated with primary-site MRI, whole-body [18F]FDG-PET, and chest CT for 5 years after treatment.

RESULTS: Five-year disease-free survival was 88% for low-risk (LR) (n=8), 76% for intermediate-risk (IR) (n=37), and 36% for high-risk (HR) (n=23) patients (P ≤ 0.01 for LR/IR vs. HR). The cumulative incidence (CIN) of local failure (LF) at 5 years for the entire cohort was 10.4%. Tumor size at diagnosis was a significant predictor of LF (P < 0.01). Patients with head and neck primary tumors (n=31) had a 35% CIN of cataracts, the risk correlating with lens dose (P = 0.0025). Jaw dysfunction was more severe when the pterygoid and masseter muscles received a mean dose of >20 Gy (P = 0.013). Orbital hypoplasia developed more frequently after a mean bony orbit dose of >30 Gy (P = 0.041). Late toxicity in patients with genitourinary tumors included microscopic hematuria (9/14), bladder-wall thickening (10/14), and vaginal stenosis (2/5).

CONCLUSION: Long-term LF rates were low, and higher rates correlated with larger tumors. Treatment-related toxicities resulting in measurable functional deficits were not infrequent, despite the conformal RT approach.

PMID: 31987969 [PubMed - as supplied by publisher]