EXTERNAL BEAM RADIOTHERAPY TREATMENT for cervical cancer Flashcards
EXTERNAL BEAM RADIOTHERAPY TREATMENT recommended for
-stages IB3,II,III and IVA-chemoradiation
-Pelvic RT with brachy (Pt not fit for surgery)
-CRT can be given in early stages (Pt not fit for surgery)
Dose Defintive chemoradiotherapy
1.8Gy (50.04Gy) + single agent radiosensitizing chemotherapy cisplatin (weekly 40mg/m2 )
followed by intra-cavitary brachytherapy
Dose Post-op:
-45-50.4Gy/25-28#/5-5.5wks
-not vaginal vault brachy unless +ve vaginal margin
CT Simulation- bladder filling
displaces small bowel and reduces volume of bladder
CT Simulation- Patient Position: prone
-bellyboard
-displace small bowel
-arms above head
PRE-TREATMENT- CT SCAN
-intraoital marker
-vaginal contrast
-contrast if no renal impairment(helps in visualizing pelvic blood vessels , uterus and primary tumour)
PRE-TREATMENT- CT SCAN scanning levels
T12- below the perinum
Possible Plans
-2 fields :ant and post (when patient has
extensive disease-palliation)
-3 fields ( anterior and wedged fields on lateral)
-4 field block (obese patients , to give better dose distribution)
PLANNING-IMRT/VMAT
decrease in acute toxicities - GI ,GU and haemotogical toxicities
Equivalent efficacy to conventional techniques with lower toxicity burden
Para-aortic Treatment
-extended field( now to T12 to L1 space) with concurrent cisplatin
-associated with high risk of high rate acute and late toxicity
possible doses for Palliative Treatment
-single 8Gy fraction
-20GY/5#/1 week
-30Gy10#/2 weeks
IGRT-WHAT NEEDS TO BE CONSIDERED?
INTACT UTERUS:
-whole uterus in volume
-the uterine movement (can be up to 3cm a/p)
-independent of bone
-bladder-filling has been shown to influence uterine motion a/p and s/i
-Movement of the cervix in AP direction for rectal filling
Post-op Pelvis
-vaginal vault moves in A/P direction w rectal filling
-little movement of vagina in LT/RT
-empty bladder might be easier to reproduce, however this increases dose to small bowel and bladder
imaging protocols for IGRT
IGRT protocols that visualize soft tissue at the time of radiotherapy
imaging protocols for Target motion in the cervix
significant changes in shape and position in CTV anatomy can occur due to changes in bladder and rectal and tumour volume.
Adaptive RT can be used to reduce margins and/or avoid dosimetric insuffiency
imaging protocols on treatment verification
3d volumetric vertification is gold standard imaging modality particulary when using IMRT
Adaptive Planning Strategies: Post-operative pelvis
two planning scans , one with a full bladder and one with a empty bladder.
images are fused and planning can create a ITV(internal tumour volume) and take account of the position in two extremes
Adaptive Planning -Uterus motion model
-create library of plans where the uterus is in different positions due to bladder filling
-take CBCT before tx and select the most apropiate plan for that day
-reduces dose in OAR
BRACHYTHERAPY :HDR-Iridium Ir192
-outpatient
-shorter tx times
-minimises radiation to staff (afterloading)
-allows tx dose optimisation with greater control and less morbidites
-intregration of EBRT and HDR - reduction in overall tx time
BRACHYTHERAPY :LDR- Cesium Cs 137
-inpatient
-strict bed rest
-radiation exposure to staff - manual loading
-high reliance for vaginal packaging -potential for displacement
Brachytherapy aim
give higher dose to tumour and sparing normal tissues
Brachytherapy usually combined
EBRT and also post-op and /or pre-op surgery
Brachytherapy dose can be delivered
Low dose rate=0.4-2Gy/hr
medium dose rate= (2- 12Gy/hr)
high dose rate=(>12Gy/hr)
Brachytherapy- conditions prior to implant
-optimal tumour reduction/shrinkage must. be achieved
-tumour regression usually occurs 2-5wks of EBRT
-review all patients before brachy
-FBC before insertion
Duration of EBRT and brachy
shouldnt exceed 56 days
-EBRT and chemo should be stopped on days of brachy
-In Ireland, intracavity brachytherapy given once EBRT has been completed. Keeping to within 56 days
Intracavity Procedure- Theatre
-general Anaesthesia, spinal or epidural
-in dorsal lithotomy position
-EUA asses :
a) residual
b)cervical and fornices anatomy
c)select appropiate applicators
-contrast or saline to visual on imaging
-dilate cervix and use ultrasound to check uterine length
Intracavity Procedure
-insert applicators
-pack vagina to keep applicator in place (vaseline soaked gauze)
-rectum retracter to minimize dose to rectum and bladder
-can suture applicator to restrict movement if needed
-transfer bed to CT or MRI
-CT scanned w applicators in place and then 3D planned
target volumes notes
-interstital brachy or a combo of interstital and intracavity brachy if tumour volume cannot be achieved by conventional brachy
Point A allows
uniformity of treatment delivery between institutions
Total Doses from Point A and external beam radiotherapy
◦80 Gy- small tumours
◦ 85 Gy or higher- larger tumours
