melanoma/sarcoma part I

what are the three types of skin cancer

basal cell

squamous cell

melanoma

what is melanoma

malignant skin cancer that occurs in melanocytes

melanoma represents what amount of skin cancer

4%

which skin cancer has the highest death rate

melanoma

which skin cancer is most likely to metastasize

melanoma

clark's system

deals with the "Level of Invasion"

breslows system

deals with the disease thickness

T

tumor size

has tumor invaded nearby tissue

N

describes regional LNs that are involved

M

describes distant metastasis

treatment options for skin cancer

surgery

chemo

RT

melanoma SIM (4)

vac loc bag

head in supine

wedged knees

arm akimbo

vac loc bag purpose

ensures reproducibility

arm akimbo purpose

prevents self bolusing of skin folds leading to desquamation

higher skin dose results in (2)

erythema and desquamation

melanoma contouring

no specific contours made by dosimetry

be mindful of the treatment field designed by the physican

how should you be mindful of the treatment field designed by the physician

are there critical structures nearby or inside the field, if so contour them

Melanoma field arrangment

usually parallel opposed beams (AP/PA or slight obliques)

critical structures noted when creating the melanoma treatment fields (4)

lung

humeral head

spinal cord

heart (if on left side)

what beam modifiers are used for melanoma (3)

mlcs

wedges

step and shoot/field in field

what is a step n shoot or control point (2)

a beam is made up of multiple segments

each segment has an individual mlc arrangement which is custom designed by the tps or dosimetrists

what is the end goals of s n s or control points

deliver homogenous distribution of dose

treat the tumor, spare the normal tissue

benefits of s n s

delivery efficiency

limitations of sns or control points

cannot change beam energy between segments

cannot change jaw settings between segments

cannot port individual films

what is field in field

each segment with its individualized mlc pattern is a separate field

what is FIF also called

forward planned IMRT

how is FIF similar to and different from SnS

goal is the same to create a homogenous dose distribution

the treatment delivery differs

FIF benefits

can change beam energy between fields

can change jaw settings between fields

can port each individual

FIF limitations

not efficient treatment delivery

each segment is an individual beam that is loaded up and treated separately

melanoma beam energt

6x or 18x depending on patient thickness

what is the most common beam energy used for melanoma and why

18 MV is most common since the target is not the skin but the lymph nodes in the axilla

melanoma prescription (2)

30 Gy in 5 fx

physician will evaluate the 2700 cGy isodose line

melanoma treatment schedule and why

Monday/Thursday

Tuesday/Friday

this fractionation patterns allows for normal tissue recovery between each dose (the radiobiological effect)

melanoma fractionation

hypofractionation: higher doses of radiation in fewer treatments than conventional radiation therapu

hypofractionation is used with melanoma treatments due to the fact that

melanoma optimization

if only given 1 field, copy and oppose to create the parallel opposed field

evaluate patient sep to determine beam energy

consider whether to use the iso or a calc point

melanoma optimization prescription normalization

normalize prescription to achieve coverage with 2700 cGy and elimate 3000 cGy

melanoma optimization beam weightings

adjust beam weighting to evenly distribute and minimize the clinically sig hot spots

max fose for melanoma

less than 3000 cGy

is it acceptable to have a max dose greater than 30 Gy on the treatment couch or the immobilization device but not in the patient

what is sarcoma

cancer developing from certain tissues like bone or muscle

what is the main type of sarcoma and where does it develop from

osteosarcoma which develops from bone and soft tissue sarcoma

where does soft tissue sarcoma develop from

soft tissue like fat, muscle, nerves, fibrous tissues, blood vessels, or deep skin tissues