Brachy Therapy

Question 1

What are clinical advantages of HDR brachytherapy?

Answer 1

Outpatient treatment 
Dose optimisation - allows for adaptive planning. 
Reduced radiation exposure for staff 
More stable positioning
Smaller applicators 
High dose rate= short treatment time

Question 2

What are clinical disadvantages of HDR brachytherapy?

Answer 2

More complex treatment and planning techniques
Compressed time frame for planning
Greater potential for error due to a much higher dose being delivered over a short timeframe
Potential for high radiation dose to staff and patient with source failure.

Question 3

What is a High Risk CTV?

Answer 3

Major risk of local recurrence - residual macroscopic tumour at time BT (smaller than at time of diagnosis)

Question 4

What is a Intermediate Risk CTV?

Answer 4

major risk of local recurrence -initial macroscopic tumour at time of diagnosis

Question 5

What is a Low risk CTV?

Answer 5

potential microscopic tumour spread -treated with surgery and/or external beam radiotherapy but not brachytherapy.

Question 6

Which imaging modality is best for brachytherapy?

Answer 6

No one method is ideal.
Useful to use a combination of two or more methods.
Can use CT/ultrasound to localise applicators and MR to outlien target volumes/ OAR.

Use MRI and CT for every fraction.

Question 7

How can inter-fraction and intrafraction variation affect brachytherapy?

Answer 7

May cause deviation from prescribed dose
More significant for HDR as the number of fractions is higher than for LDR.
Steep dose gradient around the applicators
Tumour shrinkage and normal tissue fibrosis may occur over the total length of time that HDR is delivered.

Question 8

Describe Brachytherapy dose rates.

Answer 8

Low dose rate (LDR) 0.4 -2 Gy/h
Medium dose rate (MDR) 2 -12 Gy/h
High dose rate (HDR) > 12 Gy/h

Question 9

What are clinical advantages of HDR?

Answer 9

Outpatient treatment
Dose optimisation –adaptive B/T planning
Reduced radiation exposure for staff under normal situations
More stable positioning
Smaller applicators
High dose rate= short treatment time

Question 10

What are clinical disadvantages of HDR?

Answer 10

More complex treatment and planning techniques
Compressed time frame for planning
Greater potential for error due to a much higher dose being delivered over a short time-frame
Potential for high radiation dose to staff and patient with source failure

Question 11

What is pre-treatment imaging used for in brachytherapy?

Answer 11

E.g. PET, MRI,CT
Evaluate tumour
Determine treatment modality
Determine optimum treatment volume and dose.

Question 12

What is the purpose of bracytherapy imaging for each insertion?

Answer 12

E.g. MRI, CT, US
Evaluate tumour response 
Verification of applicator position 
Define HRCTV, IRCTV, OAR
Adaptive RT

Question 13

What is post treatment imaging used for?

Answer 13

Evaluate tumour response & toxicity

Question 14

What arae the EQD2 objectives and constraints for brachytherapy?

Answer 14

D90- High Risk CTV: > 87 
D90 Intermediate Risk CTV: 70-75
D2cc Bladder:  < 90
D2cc Rectum: < 75
D2cc Sigmoid: < 75

Question 15

What are dose limiting structures for brachytherapy?

Answer 15

The Bladder is a dose limiting structure, particularly with acutely angled tandems.

The rectum is not usually a dose limiting structure due to use of an applicator with rectal retractor

Question 16

What are advantages of prostate HDR?

Answer 16

Image-guided needle placement
Optimised dose distribution 
Organ motion diminished 
Radiobiological advantage 
Remote afterloading 
Single reusable source

Question 17

What are acute clinical issues and management strategies for prostate HDR?

Answer 17

Template Catheter movement - minimise movement of patient/ bed rest

Haematuria/ clot retention - continuous bladder irrigation

Perineal discomfort and back discomfort- Analgesics

Infection Risk - prophylactic antibiotics

DVT prophylaxis - stockings/heparin

Defaecation- low residue diet prior to and during admission. s