Local staging and treatment in extremity rhabdomyosarcoma. A report from the EpSSG-RMS2005 study

Terwisscha van Scheltinga S, Marc H. W. A. Wijnen MHWA, Martelli H, Rogers T, Mandeville H, Gaze MN, McHugh K, Corradini N, Orbach D, Jenney M, Kelsey A, Chisholm J, Gallego S, Glosli H, Ferrari A, Zanetti I, De Salvo GL, Minard-Colin V, Bisogno G, van Noesel M, Merks JHM. Cancer Med. 2020 Oct;9(20):7580-7589. doi: 10.1002/cam4.3365.

Rhabdomyosarcoma of the extremities present with two main challenges: correct evaluation of initial regional nodal involvement and define adequate local treatment.

Methods: Pediatric patients with localized rhabdomyosarcoma of the extremity included in the EpSSG-RMS2005 study between 2005 and 2014 were evaluated for staging, treatment, and survival. The outcome was compared to the preceding European SIOP-MMT studies.

Results: Of the 162 patients included, histology was unfavorable in 113 (70%), 124 (77%) were younger than 10 years, 128 (79%) were IRS III, and 47 (29%) were node-positive. A regional node biopsy was performed in 97 patients (60%) and modified the lymph node stage in 15/97 (16%). Primary and delayed surgery was performed in 155 (96%) and radiotherapy delivered in 118 (73%) patients. Relapse occurred in 61 cases (38%), local in 14 (23%), regional in 13 (21%), distant in 22 (36%), and combined relapse in 12 (20%) with five progressive diseases (8%) and four secondary tumors (7%). Five-year event free (EFS) and overall survival (OS) were 58.4% (95%CI, 50.3-65.7) and 71.7% (63.6-78.4), respectively. In the previous studies MMT89 and MMT95, tumor surgery was performed in 32/53 (60%) and 74/82(90%), respectively, and radiotherapy delivered in 13/53 (25%) and 26/82 (30%), respectively. Five-year EFS and OS were 35.6%, and 50.3% in MMT89 and 54.3% and 68.2% in the MMT95 study.

Conclusions: Even if the lymph node staging was not always complete according to the RMS2005 protocol, node sampling changed lymph node status in a significant number of patients. Despite the higher rate of patients treated with locoregional radiotherapy, survival in RMS2005 did not improve compared to the previous European SIOP-MMT95 study.

Keywords: local therapy; lymph node metastases; radiotherapy; rhabdomyosarcoma; staging; surgery.