Efficacy and Safety of Limited-Margin Conformal Radiation Therapy for Pediatric Rhabdomyosarcoma: Long-Term Results of a Phase 2 Study

Radiation therapy dose escalation achieves high rates of local control with tolerable toxicity profile in pediatric and young adult patients with Ewing sarcoma

BACKGROUND

Local control for patients with Ewing sarcoma (EWS) who present with large tumors are suboptimal when treated with standard radiation therapy (RT) doses of 54-55.8 Gy. The purpose of this study is to determine local control and toxicity of dose-escalated RT for tumors ≥8 cm (greatest diameter at diagnosis) in pediatric and young adult patients with EWS.

METHODS

Eligible patients ≤30 years old with newly diagnosed EWS ≥8 cm treated with definitive conformal or intensity modulated photon, or proton radiation therapy techniques were included. All patients in the study received dose-escalated RT doses. Outcomes included overall survival (OS), event-free survival (EFS), local failure rates, and toxicity.

RESULTS

Thirty-two patients were included, 20 patients presented with metastatic disease and 12 patients with localized disease. The median RT dose was 64.8 Gy (range, 59.4-69.4 Gy) with variability of doses to protect normal surrounding tissues. All patients received systemic chemotherapy. The 5-year OS and EFS for the cohort was 64.2% and 42%, respectively. The 5-year cumulative incidence of local failure was 6.6%. There were two combined local and distant failures with no isolated local failures. Twenty-nine patients experienced short term toxicity, 90% of those being radiation dermatitis. Twenty-seven patients experienced long-term toxicity, with only one experiencing grade 4 toxicity, a secondary malignancy after therapy.

CONCLUSION

This study demonstrates that definitive RT for pediatric and young adult patients with EWS ≥8 cm provides high rates of local control, while maintaining a tolerable toxicity profile.

Prognostic factors of pediatric pelvic and genitourinary rhabdomyosarcoma: An analysis based on SEER database

Background

Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcomas in children. This study aimed to investigate the prognostic factors of pelvic and genitourinary RMS in children and evaluate the survival outcomes of these children treated with or without radiation therapy (RT).

Methods

The Surveillance, Epidemiology, and End Results Program (SEER) database was required for children with pelvic and genitourinary RMS. Overall survival (OS) and cancer-specific survival (CSS) were analyzed using the Kaplan-Meier method, log-rank test, Cox proportional hazards models, and propensity score-matched analyses.

Results

For the 262 patients analyzed, the most common biological subtypes were embryonic (n=209, 79.8%) and alveolar (n=29, 11.1%). Patients with alveolar RMS had the worst prognosis (P < 0.05). The testis (n=122, 46.6%) was the most common location, followed by the urinary bladder (n=57, 21.8%) and prostate (n=48, 18.3%). Uterus RMS had the highest survival rate, followed by testis, urinary bladder, and prostate RMS. Favorable prognostic factors were age at diagnosis < 15 years, non-alveolar histological subtype, early tumor stage (localized/regional), specific sites (uterus and testis), and treatment (cancer-directed surgery and chemotherapy) (P < 0.05). Propensity score-matched analyses comparing the cohorts of patients treated with or without RT demonstrated no significant differences in prognostic survival (OS: P=0.872, CSS: P=0.713).

Conclusion

The nomogram constructed based on independent prognostic factors may accurately predict survival rates at 1 and 5 years. Surgery and adjuvant chemotherapy can be effective treatments, but RT fails to guarantee a survival benefit. Therefore, prospective trials evaluating RT for pediatric pelvic and genitourinary RMS are warranted.

Evaluation of treatment-associated eye toxicity after irradiation in childhood and adolescence-results from the Registry of the Evaluation of Side Effects after Radiotherapy in Childhood and Adolescence (RiSK)

Purpose

The aim of the study is to evaluate treatment-related acute and late eye toxicity associated with radiation therapy in childhood and adolescence as correlated with RT (radiotherapy) doses.

Methods

From 2001 to 2016, a total of 1725 children and adolescents undergoing radiation therapy were prospectively documented in the Registry of the Evaluation of Side Effects after Radiotherapy in Childhood and Adolescence (RiSK). The RTOG/EORTC criteria were used to classify ocular acute and late effects. Uni- and multivariate analyses were carried out to evaluate the impact of patient age, pre-existing impairments, and radiation dose on ocular toxicity.

Results

Of all documented patients, 593 received dose to the eye and formed the basis of this analysis. In 435 patients, information on acute reaction was available and graded 1, 2, 3, and 4 in 49, 17, 0, and 2 patients, respectively. Information on late toxicity was available in 268 patients and graded 1, 2, 3, and 4 in 15, 11, 11, and 5 patients, respectively. The acute toxicity rate was significantly higher in children who received a maximum dose > 50 Gy to the eye (p < 0.001) and who had a pre-existing eye impairment (p < 0.001 in multivariate analysis). The development of late toxicity was significantly higher for patients experiencing acute toxicity and having received a radiation dose > 50 Gy.

Conclusion

Acute and late toxicity both correlate with high radiation dose to the eye (> 50 Gy) and acute toxicity additionally with pre-existing eye impairments.