Radiation-induced sarcomas of the head and neck

Table 1 Summary of key findings

With improved oncologic outcomes, RIS are increasingly seen in long-term survivors of head and neck cancers

There is no subsite predilection; They can arise in any irradiated tissue of mesenchymal origin

Common histologic subtypes parallel their de novo counterparts

Imaging features of RIS are not pathognomonic but large size, extensive local invasion with bony destruction, and marked enhancement within a prior radiotherapy field are suggestive of a diagnosis of RIS

RIS development may be influenced by factors such as radiation dose, age at initial exposure, exposure to chemotherapeutic agents, and genetic tendency

Precise pathogenetic mechanisms of RIS are poorly understood

Management is challenging, entailing surgery in irradiated tissue and limited scope for further radiotherapy and chemotherapy

RIS is associated with significantly poorer outcomes than stage-matched de novo sarcomas

Surgical resection with clear margins appears to offer the best chance for cure

RIS: Radiation-induced sarcomas.

Table 2 Advantages and disadvantages of computed tomography and magnetic resonance imaging in head and neck oncologic imaging

CT	MRI
Advantages
Fast	Superior soft tissue resolution including better assessment of perineural invasion, intracranial extension of disease, marrow infiltration
Well tolerated	Multi-planar imaging capability, better definition of cradiocaudal extent
Relatively inexpensive	Less image degradation caused by artifacts arising from dental amalgam
Provides assessment of tissue composition (vascularity, lipid content etc.)	Does not involve ionizing radiation
Ideal at demonstrating cortical bone erosion	Contrast material is less likely to produce allergic reaction
Disadvantages
Involves exposure to small amounts of radiation	May take more time to perform
Inferior soft tissue resolution compared with MRI	More expensive
Higher risk of allergic reactions and nephrotoxicity associated with the use of iodinated contrast agents	Lower patient tolerance; Claustrophobic patients may need sedation
	Contraindicated in patients with pacemakers and other implanted metallic devices which may malfunction following exposure to strong magnetic fields
	More susceptible to motion artefact

CT: Computed tomography; MRI: Magnetic resonance imaging.

Table 3 TNM staging for soft tissue sarcoma

Primary tumor (T)
TX	Primary tumor cannot be assessed
T0	No evidence of primary tumor
T1	Tumor 5 cm or less in greatest dimension
T1a	Superficial tumor
T1b	Deep tumor
T2	Tumor more than 5 cm in greatest dimension
T2a	Superficial tumor
T2b	Deep tumor
Regional lymph nodes (N)
NX	Regional lymph nodes cannot be assessed
N0	No regional lymph node metastasis
N1	Regional lymph node metastasis
Distant metastasis (M)
M0	No distant metastasis
M1	Distant metastasis
Histologic grade (G)Δ
GX	Grade cannot be assessed
G1	Grade 1
G2	Grade 2
G3	Grade 3
Anatomic stage/prognostic groups
Stage IA	T1a	N0	M0	G1, GX
	T1b	N0	M0	G1, GX
Stage IB	T2a	N0	M0	G1, GX
	T2b	N0	M0	G1, GX
Stage IIA	T1a	N0	M0	G2, G3
	T1b	N0	M0	G2, G3
Stage IIB	T2a	N0	M0	G2
	T2b	N0	M0	G2
Stage III	T2a, T2b	N0	M0	G3
	Any T	N1	M0	Any G
Stage IV	Any T	Any N	M1	Any G

Table 4 TNM staging for bone tumors other than lymphoma and myeloma

Primary tumor (T)
TX	Primary tumor cannot be assessed
T0	No evidence of primary tumor
T1	Tumor 8 cm or less in greatest dimension
T2	Tumor more than 8 cm in greatest dimension
T3	Discontinuous tumors in the primary bone site
Regional lymph nodes (N)
NX	Regional lymph nodes cannot be assessed
N0	No regional lymph node metastasis
N1	Regional lymph node metastasis
Distant metastasis (M)
M0	No distant metastasis
M1	Distant metastasis
M1a	Lung
M1b	Other distant sites
Histologic grade (G)
Grade is reported in registry systems by the grade value. A two-grade, three-grade, or four-grade system may be used. If a grading system is not specified, generally the following system is used:
GX	Grade cannot be assessed
G1	Well differentiated-low grade
G2	Moderately differentiated-low grade
G3	Poorly differentiated-high grade
G4	Undifferentiated-high grade
Anatomic stage/prognostic groups
Stage IA	T1	N0	M0	G1, 2 Low grade, GX
Stage IB	T2	N0	M0	G1, 2 Low grade, GX
	T3	N0	M0	G1, 2 Low grade, GX
Stage IIA	T1	N0	M0	G3, 4 High grade
Stage IIB	T2	N0	M0	G3, 4 High grade
Stage III	T3	N0	M0	G3, 4 High grade
Stage IVA	Any T	N0	M1a	Any G
Stage IVB	Any T	N1	Any M	Any G
	Any T	Any N	M1b	Any G

Table 5 TNM staging system for rhabdomyosarcoma

Stage	Sites	Tumor stage invasiveness	T stage size	N	M
1	Orbit Head and neck Genitourinary Biliary tract	T1 or T2	a or b	Any N	M0
2	Bladder/prostate Extremity Cranial parameningeal OtherΔ	T1 or T2	a	N0 or NX	M0
3	Bladder/prostate Extremity Cranial parameningeal OtherΔ	T1 or T2	a b	N1 Any N	M0
4	All	T1 or T2	a or b	N0 or N1	M1

T: Tumor stage; T1: Confined to anatomic site of origin; T2: Extension; a: ≤ 5 cm in diameter; b: > 5 cm in diameter; N: Regional nodes; N0: Not clinically involved; N1: Clinically involved; NX: Clinical status unknown; M: Metastases; M0: No distant metastases; M1: Distant metastases present.