breast cancer part III

what is another word for tangential ports

glancing

what does tangential ports limit dose to

underlying structures like the lung and heart

what can tangentials be used for

intact breast or post mastectomy chest wall

what energy photon beams are ideal for tang ports

low energy (6-10MV)

what method is used for treating tagnents

isocentric

what else can be another technique used with tangents besides isocentric

deep posterior margin

what is the main key factor in all techniques

maintaining a coplanar posterior margin

what does coplanar mean

same plane

why must you consider transmission with a split field

due to the dose to heart, lung, and other breast

t/f: it can be accomplished by tangent fields that are not parallel opposed

true

what is included in the superior border of the intact breast/chest wall margins

• as far cephalad as possible without including the arm

• first intercostal space

• superior extent of the palpable breast tissue

• cephalad to original location of mass

• level with angle of louis

what is included in the inferior border of the intact breast/chest wall margins

caudal 1-2cm to the inframammary fold

if the patient is getting treated post mastectomy, how do you determine the inferior border

evaluating the contralateral breast

what is included in the medial border of the intact breast/chest wall margins

midline of pt by palpating the suprasternal notch and xiphoid process

what are the exceptions of the medial border

pts whose mass/incision extends to or beyond midline and pts who will receive IM irradiation

what is included in the lateral border of the intact breast/chest wall margins

at pts midaxillary line

what is a pts midaxillary line at

drawn from center of the pts axilla in a caudad direction

what do you want to include in the lateral border

drain sites, incisions considered at risk, original tumor bed, and appropriate amount of lung margin

why is the lateral margin most often adjusted

you may have to alter the amount of lung in port

what treatment is one of the most challenging and high volume procedures performed in a XRT department

breast

what is the ideal method set up for the pt

setting up to triangulation points

where is the tangential field set up mark location

anterior chest overlying sternum

what can be done daily in addition to images of tangents

port films

what is done with the table after you do your set up marks

raise the table to a specifiic SSD and shift it laterally to place isocenter in the correct location within breast

what is the superior border for the field with supraclavicular border

what do you want to avoid on the superior border of supraclavicular

flash over the skin

what is the medial border for the field with supraclavicular borders

midpoint of the SSN

what is the lateral border for the field with supraclavicular borders

approx 2-3cm of the humeral head

what is the inferior border for the field with supraclavicular borders

at the angle of louis; just above the superior extent of the palpable breast tissue; point greater than 2cm cephalad to original location mass

what is the gantry angle on the supra borders

10-15 degrees mediolaterally

why is the gantry rotated 10-15 degrees mediolaterally for supra

to avoid exit through spinal cord

where is the central ray of supra

what does PAB stand for

posterior axillary boost field

what is is a PAB used to do

increase midaxillary dose

why is PAB done

because dose from anterior supra alone may be insufficient for postiive nodes at high risk

what does PAB use identical like the supra port

inferior margin

how will the PAB field be different that the supra

it will be smaller

what is the superior margin for a PAB

mid to upper clavicle

what is the medial margin for a PAB

a strip of lung approx 1 cm wide

what is the lateral margin for a PAB

approx 1-2cm of humeral head

what is the inferior margin for a PAB

corresponding to inferior border of supra

how is a PAB prescribed

quantity sufficient

how is a PAB fractions treated

same as supra, but dose contributed from supra must be considered

what is the one major exception in the set up for tangential breast fields with supra and a PAB being treated

make a correction for the divergence of the tang fields into the supra/axilla

how is the one major exception of tang fields with supra/PAB done

rotating couch AWAY from gantry

what is the couch kick based off of

the length of the tangent port

what does rotating the couch do

eliminate impact of divergence into the supra/axilla fields

what is one method for treating IM nodes

extend medial border beyond midline by approx 3cm

what does extending the medial border do

increases lung volume

when treating IM nodes what is not desired if you are treating left breast)

because of the heart

what is another way to treat IM nodes

en face IM field with combo of electrons and photons (machline)

what does overlap result in

hot or overdosed areas; possible matchline fibrosis and poor cosmetic results; overdose to lung

what does underdose provide

potential for tumor recurrence

what does conservative XRT often include

boost to tumor bed after completing tangent ports

what is the most common way to treat boost

electrons

what is another way to treat boost besides electrons

brachytherapy

why must the boost be planned

so the correct tissue is boosted and that the electron energy is appropriate for the tissue depth

what is an inaccurate assumption made when dealing with boost

the scar reflects position/size of tumor bed

what can