Rhabdomyosarcomas

Key points

Commonest soft tissue sarcoma

3rd commonest extracranial

Bimodal distribution - ages 2-6, 10-18

Histological types

Embryonal Rhabdomyosarcoma (ERMS)

• Most common type

• Typically affects younger children

• Common sites: head and neck region, genitourinary tract

Alveolar Rhabdomyosarcoma (ARMS)

• More aggressive than ERMS

• Often occurs in older children and adolescents

• Common sites: extremities, trunk, perineum, and pelvis

  
  

Spindle Cell/Sclerosing Rhabdomyosarcoma

• Spindle cell type often seen in paratesticular region of young males

• Sclerosing type can be more aggressive and may mimic other sarcomas

Botryoid Rhabdomyosarcoma

• Typically found in mucosal-lined structures such as the vagina, bladder, or nasopharynx

• Named for its grape-like appearance

Anaplastic (Pleomorphic) Rhabdomyosarcoma

• Very rare - usually found in adults

• Typically found in the extremities

• Large nuclei

• Poor prognosis compared to other types

Best prognosis: Orbit

Worst prognosis: Retroperitoneal

Genetics

Alveolar RMS is characterised by translocations

FKHR transcription factor (FOXO1) gene from chromosome 13 can fuse with either the PAX3 (chromosome 2) or PAX 7 (chromosome 1) transcription factor gene = PAX/FKHR fusion

PAX3 fusion - worse survival

CCLG recommends that any RMS with a PAX 3 or PAX7-FOXO1 fusion, it should be treated as alveolar irrespective of its actual histological type

25% of alveolar RMS are translocation negative and have similar behaviour and prognosis to embryonal RMS

Associations

Li Fraumeni

NF1

Process of staging and risk grouping in order:

Intergroup Rhabdomyosarcoma Studies (IRS) grouping (post resection)

Summary of CCLG Interim guidelines for the treatment of rhabdomyosarcoma table:

Low Risk Group

• Pathology: Favourable

• Post surgical stage: I

• Node stage: N0

• Treatment: VA (8 cycles) + Surgery

Standard Risk Group

• Pathology: Favourable

• Post surgical stage: I, II, III

• Node stage: N0

• Treatment: IVA (4-5 cycles) + VA (4-5 cycles) + Surgery ± Radiotherapy

High Risk Group

• Pathology/Size/Age: Unfavourable

• Post surgical stage: I, II, III

• Node stage: N0 or N1

• Treatment: IVA (9 cycles) + 6 months maintenance + Radiotherapy

Very High Risk Group

• Pathology: Unfavourable

• Post surgical stage: I, II, III

• Node stage: N1

OR

• Metastatic

• Pathology: All

• Post surgical stage: IV

  
  

• Treatment: IVADo (4 cycles) + IVA (5 cycles) + 12 months maintenance + Radiotherapy

  
  
  
  

Local treatment algorithm

Adapted from EpSSG European Surgery Guidelines for Rhabdomyosarcoma 2022

Principles of surgery

Surgery should include margin of healthy tissue, close collaboration between pathologist and surgeon - detailed drawings and markings on specimen for orientation

Biopsy track should be included in eventual resection or RT field

Avoid mutilating surgery as a first procedure - unless retroperitoneal

Surgical nodal staging - Sentinel lymph node biopsy (SLNB) if possible for:

Extremity tumours

>10 years + paratesticular tumour

Alveolar/fusion positive tumours

Radiotherapy if still unresectable or if mutilating surgery needed

Repeat resection or Radiotherapy if +ve margins

Biliary RMS - complete resection not often possible - good outcomes with chemo + radio

Chest wall

Upfront resection unless

• >5cm

• Unresectable

○ span > ribs + require resection 5 ribs

○ abutting the scapula/sternum

○ intraspinal extension/neurovascular involvement

keep 0.5cm margin - include biopsy site - however gross total resection + radiotherapy is adequate

Retroperitoneal - need aggressive surgery

Bladder prostate - complete resection, prostatectomy if needed - bladder salvage in 50-60%

Paratesticular - Radical inguinal orchiectomy + retroperitoneal lymph node dissection if patient ≥10 years of age OR if LN involvement on staging in younger patients

Templates for RPLND in right and left tumours

Vaginal - regresses well with chemo - surgery rarely needed - Vaginectomy and hysterectomy should only be performed for persistent or recurrent disease

Limbs - limb sparing surgery appropriate in most

Standard scenario

Patient with lump

History:

Duration, size change

Functional impairment

Family history of tumour syndromes e.g. Li Fraumeni

Examination:

Tumour size and consistency

Tissue layer tumour is fixed to

Regional lymph nodes

USS then MRI

Oncology MDT

CT CAP

Brain MRI

BM aspirates

LP for CNS infiltrate

Whole body MR/PET/Bone scan for staging

Modified TNM staging based on favourable or unfavourable sites

In a favourable site - a non-metastatic tumour of any size or LN status is stage 1

Primary resection not suitable if LN involved

Treatment based on European Paediatric Soft Tissue Sarcoma Study Group guidelines

Proceed to local control algorithm

Post op treatment summary based on: Intergroup Rhabdomyosarcoma Studies (IRS) grouping (post resection)

Chemotherapy + radiotherapy:

Vincristine + Act D for all

Add ifosfamide + Radiotherapy if anything other than Low risk

Add Doxorubicin if very high risk

Children with metastatic disease will receive 12 months of maintenance vinoralbine and cyclophosphamide

References

EpSSG European Surgery Guidelines for Rhabdomyosarcoma 2022

CCLG Interim guidelines for the treatment of rhabdomyosarcoma: CCLG Soft Tissue Sarcoma Special Interest Group, March 2019, Updated April 2021

Weerakkody Y, Deng F, Jones J, et al. Botryoid rhabdomyosarcoma. Reference article, Radiopaedia.org (Accessed on 20 Jul 2024) https://doi.org/10.53347/rID-7851