Soft Tissue Sarcomas

STSs occur in ____ tissues that provide connection, support, and locomotion

connective (mesenchymal)

where can STSs appear?

any mesenchymal tissue in the body

most common site of STS

extremities (60%), especially the proximal thigh

other than the extremities, primary sites where STS is found

trunk (19%), retroperitoneum (15%), head and neck (9%)

STS makes up ___% of all cancers

less than 1%

are bone cancers or STS more common?

STS, but still less than 1% of all cancers

how many subtypes of STS exist?

more than 50

most common STS subtypes in adults

liposarcoma, leiomyosarcoma, MFH, GIST, synovial sarcoma

most common STS in children

rhabdomyosarcoma

MFH

malignant fibrous histiocytoma (pleomorphic sarcoma)

one of the most common STS in adults

GIST

gastrointestinal stromal tumor

one of the most common STS in adults

the two most common STS in adults

liposarcoma and leiomyosarcoma

STS makes up ___% of cancers in adults but ___% of cancers in children

about 1% adults, 15% children

which sex has higher incidence of STS?

men

most common age for STS

50s-60s, but can happen at any age

STS is more common in what racial group?

Black

overall etiology of STS

essentially unknown

some possible etiological links for STS

radiation exposure, NF, RB1 gene defects (retinoblastoma), environmental factors, Li-Fraumeni syndrome (mutation of TP53 suppressor gene), EBV and HIV

viral etiological links to STS

EBV and HIV

genetic links to STS etiology

NF, RB1 gene (retinoblastoma) defects, Li-Fraumeni syndrome - mutation of TP53 gene which normally suppresses cancer

STS arises from ___ , which gives rise to ___

primitive mesoderm, common connective tissues such as pleura, peritoneum, pericardium, blood vessels, bone, cartilage, muscles

describe the growth patterns for STS

local growth patterns follow lines of least resistance

compressed normal and fibrotic tissues that form as STS grows

pseudocapsules

primary clinical presentation of STS

painless mass that grows over weeks/months

overall clinical presentation of STS

painless mass. pain may be worse at night. secondary symptoms: paralysis, neuralgia, ischemia

a clinical presentation of STS that is a bad sign

warm skin and distended vessels

which area of STS is usually diagnosed earliest?

head and neck, because of visibility of the mass, symptoms

diagnostic imaging for retroperitoneal STS and mets to lungs

CT

main diagnostic imaging for STS and why

MRI

essential in localization, showing relationships to blood supply, nerves, tendons, muscles, fascia, and bone; superior to CT in differentiating normal vs. abnormal tissue

imaging tests used for STS detection and diagnosis

CT for retroperitoneal and lung mets

CXR - lung mets

PET

MRI - best overall

type of biopsy typically used for STS diagnosis

core needle biopsy

most critical predictor of prognosis for STS

grade

g1 = low grade, well-differentiated

g3 = high grade, poorly-differentiated

how are the subtypes of STS named?

according to the tissues they arise in

two main routes of spread for STS

direct extension and hematogenous

lymphatics not common, but bad prognostic indicator if present

main site of mets for STS

lung

sites of mets for STS

lung, then bone, liver, skin

main treatment techniques for STS

surgery for sure, maybe with RT and/or chemo

when is surgery alone effective for STS treatment?

if margins are clear after surgery

what does radical resection of STS look like?

remove all structures in every involved compartment

kind of surgery used for STS to avoid amputation

limb-salvage surgery

advantages of pre-op RT for STS

smaller treatment volume possible

less aggressive surgery if tumor shrinks

no seeding from surgery

no delay in starting treatment

smaller field size (need wider margins post-op in case of seeding)

disadvantages of pre-op RT for STS

impaired wound healing

must wait 3+ weeks before surgery

dose for pre-op RT for STS

approximately 50 Gy. may do additional RT boost after surgery if margins are close or positive, or high grade.

why would a boost be used for pre-op RT for STS?

additional boost after surgery if close or positive margins or high grade

when treating an extremity for STS, why must it be moved away from the body?

to minimize scatter radiation to the body and allow more options for beam angles

reasons for using post-op RT for STS

if pre-op is not feasible

high-grade tumors with positive margins

disadvantage of post-op RT for STS

lymphedema in extremities due to scar tissue + RT

dose and fields for post-op RT for STS

high dose. 60-66 Gy to achieve local control.

fields include the full surgical margins with 3-6 cm border. typically nodes are not included.

describe the shrinking field technique for STS radiation

10 cm margin treated to 45-50 Gy

5 cm margin to 55-60 Gy

2-3 cm margin to 60-75 Gy

scar included in each field. electron boost may be necessary.

why is a strip left open when treating an STS in the extremity with RT?

1-3 cm strip to avoid lymphedema

brachytherapy for STS is usually done with ___ placed during surgery

catheters

most common sources for STS brachytherapy

Iridium 192. loaded 5 days post-op to avoid wound healing problems

Iodine 125. retroperitoneal and head and neck cases

dose for intraoperative RT for STS

1000-2000 cGy of electrons to the tumor while sparing surrounding tissues

STS requires ___ dose to achieve local control and long-term survival

high dose

pre-op RT dose for STS

5000 cGy

post-op RT dose for STS

shrinking field delivers 6500 cGy, may go as high as 7500 cGy with electron boost