Peds Sarcoma - Rhabdomyosarcoma

About this video

• Video Title: Peds Sarcoma - Rhabdomyosarcoma
• Channel: Rad Onc Talks
• Speakers: Ria
• Duration: 01:20:52

Overview

This video provides a comprehensive overview of rhabdomyosarcoma (RMS), the most common pediatric soft tissue tumor. It covers the tumor's characteristics, common locations, risk factors, workup, staging, and treatment paradigms, including surgery, chemotherapy, and radiotherapy, supported by relevant studies.

Key takeaways

• Rhabdomyosarcoma is the most common pediatric soft tissue tumor, typically a small round blue cell tumor, and responds well to chemotherapy and radiation.
• RMS is broadly divided into embryonal (60% of cases, better prognosis) and alveolar (20% of cases, worse prognosis) histologies.
• Favorable sites for RMS are summarized by the mnemonic BONG (Biliary, Orbit, Non-paramenial head and neck, Genitourinary excluding bladder/prostate), while unfavorable sites include paramenial head and neck locations and bladder/prostate.
• Treatment involves surgery (when possible), chemotherapy (VAC regimen), and radiation for most patients, with specific protocols depending on risk stratification (low, intermediate, high).
• Risk stratification is complex, considering histology, genetics (fusion status), tumor location, and surgical outcomes, impacting chemotherapy duration and radiation doses.

The main histologies of rhabdomyosarcoma are embryonal and alveolar.

Embryonal histology is more common, accounting for about 60% of cases. It has small round cells with variable differentiation and generally has a favorable prognosis.

Alveolar histology is less common, representing about 20% of cases. It features small round blue cells that are undifferentiated and tends to have a worse prognosis. This histology is often associated with specific chromosomal translocations, such as PAX3-FOXO1.

Yes, there's a mnemonic to remember the favorable sites for rhabdomyosarcoma: BONG.

Here's what it stands for:

• Biliary
• Orbit
• Non-paramenial head and neck
• Genitourinary (specifically, non-bladder and non-prostate sites like the paratesticular, vulva, vagina, and uterus)

All other sites not included in "BONG" are considered unfavorable. This includes:

• Paramenial head and neck locations (e.g., infratemporal fossa, middle ear, mastoid, nasopharynx, nasal cavity, paranasal sinuses, parapharyngeal spaces, pterygopalatine fossa).
• Bladder and prostate within the genitourinary system.
• Kidney.
• Extremities (while considered favorable in some contexts, they can be unfavorable if they have other risk factors).
• Trunk and other locations not listed under "BONG" can also be unfavorable depending on other factors.

The standard chemotherapy backbone for rhabdomyosarcoma is the VAC regimen, which stands for:

• Vincristine
• Actinomycin D (also known as Dactinomycin)
• Cyclophosphamide

The duration of chemotherapy varies based on the patient's risk group:

• Low-risk patients typically receive 24 weeks of chemotherapy.
• Intermediate-risk patients typically receive 42 weeks of chemotherapy.
• High-risk patients typically receive 54 weeks of chemotherapy.

The general principles for radiation therapy in rhabdomyosarcoma are:

• Radiation is typically recommended for most patients with rhabdomyosarcoma.
• It is often delivered concurrently with chemotherapy, usually starting around week 13 of treatment for low and intermediate-risk patients, and week 20 for high-risk patients.
• When radiation is given concurrently with chemotherapy, Actinomycin D is typically held to avoid exacerbating toxicities.
• The radiation dose is generally 36 Gray (Gy) for most patients who have undergone surgery or biopsy.
• Higher doses (e.g., 50.4 Gy or 59.4 Gy) are used for patients with gross residual disease after surgery, depending on tumor size, or for specific metastatic sites.
• Doses are adjusted for orbital tumors, with 45 Gy if there's a complete response to chemotherapy and 50.4 Gy if there's an incomplete response.

Patients who may be able to omit radiation are a specific subset of low-risk patients:

• These are patients with embryonal histology (fusion-negative).
• They must have had a complete resection (Group 1 status), meaning a gross total resection with negative margins and negative nodes.
• This applies regardless of whether the primary tumor was in a favorable or unfavorable site, as long as they achieved a complete resection.

Here are some topics and tags that can help you explore this video in detail:

Topic	Tags
Rhabdomyosarcoma Epidemiology	Pediatric cancer, soft tissue sarcoma, incidence, male predominance, age distribution
Rhabdomyosarcoma Histology	Embryonal histology, alveolar histology, botrioid, spindle cell, prognosis, differentiation
Rhabdomyosarcoma Genetics	PAX-FOXO1 fusion, PAX3-FOXO1, PAX7-FOXO1, loss of heterozygosity 11p15, N-Myc amplification, ploidy
Rhabdomyosarcoma Sites & Risk	Favorable sites, unfavorable sites, BONG mnemonic, paramenial spaces, genitourinary, head and neck
Rhabdomyosarcoma Workup & Staging	History, physical exam, labs, imaging (CT, MRI, PET), bone marrow biopsy, LP, CSF cytology, IRSG
Rhabdomyosarcoma Pre-operative Staging	Stage 1, 2, 3, 4, favorable sites, unfavorable sites, size, nodal status, metastatic status
Rhabdomyosarcoma Post-operative Grouping	Group 1, 2, 3, 4, extent of resection, gross total resection, microscopic residual, margins, nodes
Rhabdomyosarcoma Risk Stratification	Low risk, intermediate risk, high risk, combination of factors, ARST1421, Oberlin risk factors
Rhabdomyosarcoma Treatment - Surgery	Gross total resection, maximal safe resection, non-morbid surgery, incisional biopsy, delayed excision
Rhabdomyosarcoma Treatment - Chemotherapy	VAC regimen, vincristine, actinomycin D, cyclophosphamide, duration by risk group, VACVI, VDC
Rhabdomyosarcoma Treatment - Radiation	Radiation timing, doses (36 Gy, 41.4 Gy, 50.4 Gy, 59.4 Gy), concurrent chemo, dose reduction, GTV/CTV/PTV
Rhabdomyosarcoma Evidence-Based Studies	IRS studies (D9602, ARST0331, ARST0531), D983 trial, ARST11431, pediatric oncology trials
Rhabdomyosarcoma Specific Locations	Orbital RMS, pediatric GU RMS, head and neck RMS, extremity RMS
Pediatric Sarcoma Management	Multidisciplinary approach, pediatric oncology, radiation oncology, pediatric surgery
Clinical Trials in Pediatric Oncology	Treatment protocols, study design, trial endpoints, chemotherapy regimens, radiation techniques