Patterns of Failure in Pediatric Rhabdomyosarcoma Following Proton Therapy
Menée à partir de données portant sur 66 patients pédiatriques atteints d'un rhabdomyosarcome non métastatique traité entre 2007 et 2013 par protonthérapie (âge médian : 4,1 ans), cette étude évalue le taux actuariel de contrôle local à 2 ans, puis identifie les formes de récidive
Purpose : We report on the patterns of failure in children with rhabdomyosarcoma treated with proton therapy. Patients and Methods : Between February 2007 and November 2013, 66 children with a median age of 4.1years (range, 0.6-15.3 years) diagnosed with non-metastatic rhabdomyosarcoma were treated with proton therapy. Clinical target volume 1 (CTV1) was defined as the prechemotherapy tumor plus a 1-cm anatomically-constrained margin. CTV2 was defined as the postchemotherapy tumor (or tumor bed) plus a 0.5 cm anatomically-constrained margin, further expanded to encompass potential pathways of spread, including soft tissue infiltrated with tumor at diagnosis. Results : Of the 66 children, 11 developed locally progressive disease at a median of 16 months (range, 14-32 months) for an actuarial 2-year local control rate of 88%. Among the children who progressed, median age and tumor size at diagnosis were 6.7 years (range 0.6-16 years) and 6 cm (range, 2-8 cm), respectively. Of the recurrences, 64% and 36% were embryonal and alveolar, respectively. Disease progression was observed in 7 (64%) parameningeal, 2 (18%) head and neck (other), and 2 (18%) bladder/prostate subsites. At diagnosis, 8 of 11 patients who developed a recurrence were Intergroup Rhabdomyosarcoma Study stage 3 and all 11 were group III. Of the relapses, 100% (11/11) were confirmed as in-field within the composite 95% isodose line. One of the 11 patients (9%) developed a new simultaneous regional nodal recurrence outside of the previously treated radiation field. Conclusion : Early data suggest that the sharp dosimetric gradient associated with proton therapy is not associated with an increased risk of marginal failure. Routine use of a 0.5- to 1-cm CTV1/2 margin with highly conformal proton therapy does not compromise local control in children diagnosed with rhabdomyosarcoma with unfavorable risk features.
http://www.redjournal.org/article/S0360-3016(16)33143-1/fulltext