Surgical nodal staging in rhabdomyosarcoma of the bladder and/or prostate with or without nodal or metastatic spread. A report from the European Paediatric Soft-Tissue Sarcoma Study Group (EpSSG)

Background: Risk stratification of rhabdomyosarcoma (RMS) requires accurate staging, with histological nodal assessment being of critical importance for specific tumour sites. This report explores the value of surgical nodal staging in bladder-prostate rhabdomyosarcoma (BP-RMS). Procedure: Patients with BP-RMS enrolled in the RMS2005 and MTS2008 trials (2005–2016) were reviewed for the staging methodology and outcome. Results: Significant differences in 5-year overall and progression-free survival were observed for the 224 patients with BP-RMS of different Tumour-Node-Metastasis (TNM) stages (p < 0.0001). Nodal staging was by imaging in all but 7/224 (3.1%) patients at presentation. Despite the opportunity for nodal sampling at surgery in 175 patients, no nodes were obtained in 120/175 (68.6%). Nodal sampling at surgery after 4–8 chemotherapy cycles in 48 patients, identified tumour in 6/37 (16.2%) patients considered N0 by imaging (all aged <10 years with favourable histology >5 cm tumours) and observed no tumour in 8/11 (72.7%) deemed N1, prompting changes to local therapy in 9/14 (64.3%). Overall, surgical nodal assessment did not impact on local/nodal progression/relapse (12/55, 21.8%) as compared to staging by imaging alone (29/166, 16.9%, p = 0.548; data missing for 3 patients). Pathological nodal assessment also failed to show benefit on locoregional events for patients with significantly poorer outcome, namely those aged ≥10 years (p = 0.446) or with unfavourable histology (p = 0.613). The specific targeting of nodal basins by radiotherapy showed no impact on outcome (p = 1.000). Conclusions: In contrast to other sites, surgical nodal sampling, undertaken in 24.6% (in 3.1% at diagnosis), does not significantly impact outcome of BP-RMS, despite imaging-pathological discordance prompting changes to treatment for affected patients.