Lec 4 RadB 2 Part 2

Question 1

What are the five major causes of unscheduled interruptions in a course of radical radiotherapy?

Answer 1

Machine and staff availability 
Public holidays 
Transport problems 
Medical problems 
Social circumstances that lead to a patient's failure to attend for treatment

Question 2

What is an example and management of Machine and staff availability

Answer 2

breakdowns

manage with adequate staff

Question 3

What is an example and management of Public Holidays?

Answer 3

at least 7 bank holidays per year

ideally all patients should be treated on public holidays but this may not be practical

Question 4

What is an example and management of Transport problem?

Answer 4

ambulance

efficient communication with local ambulance service

Question 5

What is an example and management of Medical Problems?

Answer 5

intercurrent disease or as a consequence of acute radiation reactions
(management of acute side effects)

Question 6

What is an example and management of Social circumstances that lead to a patient’s failure to attend for
treatment as scheduled b

Answer 6

patient is not prepared to co-operate and attend daily for therapy
(psychological and social work support)

Question 7

What are the 6 steps in BED Calculations?

Answer 7

Calculate the normal tissue BED 
Determine the respective pre-gap
The difference
Review the various treatment options
For the selected options
Review the final tumour and normal tissue BEDs

Question 8

What needs to be done in step 1 calculate the normal tissue BED?

Answer 8

for the prescribed schedule using
Eq(A). This calculation should make use of the dose actually
received by the critical normal tissue, if this is different from the
prescribed tumour dose.

Question 9

What needs to be done in step 2 Determine the respective pre-gap?

Answer 9

normal-tissue BED, also using

Eq(A).

Question 10

What needs to be done in step 3 The difference?

Answer 10

between the BEDs calculated in (1) and (2)

determines the late-normal BED ‘still to give’ (the post-gap BED)

Question 11

What needs to be done in step 4 Review the various treatment options?

Answer 11

For example, twice-daily fractionation and hyperfractionation,
increased fraction sizes, and so on) to
ascertain which will be likely to produce the minimum
extension to the treatment time, then calculate the
required dose per fraction to achieve the required latenormal
BED value

Question 12

What needs to be done step 5 For the selected option?

Answer 12

calculate the associated tumour
BED using Eq(B), remembering to make allowance for the
extended time.

Question 13

What needs to be done step 6 Review the final tumour and normal tissue BEDs

Answer 13

which

will result from the preferred compensation option

Question 14

What are 5 methods for dose compensation?

Answer 14

1. Treat on weekends
2. treat twice daily
3. increase dose per fraction for same number of post-gap dyas as there were gap days
4. use smaller number of larger fractions after the gap
5. accept treatment extension is unavoidable and deliver extrafractions using increased dose per fraction to minimise the extension duration

Question 15

What are the advantages and disadvantage of retreatment after RT (reirradiation)?

Answer 15

possible in various sites with reduced doses and with a high price in terms of morbidity
reirradiation with 50 to 60 Gy within a few years of the inital treatment improves local control and possibly survival, but with severe toxicity and functional sequelae

Question 16

What must be considered in retreatment after RT?

Answer 16

1. dose and volume treated during the initial RT and the extent of overlap of the retreatment and initial fields
2. Whether chemo was added to the initial RT
3. The time interval that has elapsed since the initial RT
4. The tissues and organs involved (they differ in their ability to recover)
5. Highly conformal technqiues (SBRT) or brachytherapy are most appropriate
6. Whethere there are alternative options to RT that could be considered

Question 17

What is the double trouble phenomenon?

Answer 17

dosimetric hot spots receive not only a higher total dose but also a higher dose per fraction