Multi-Phase Planning @ SIM Integrated Flashcards
Why should we not just focus on the SUM PLAN?
Because when treating sequential boost you will treat phase 1 and phase 2 separately.
Do we have a GTV and CTV for the prostate?
The prostate is both the GTV and CTV.
What are the PTV margins for the prostate?
1cm SUP and INF
0.5cm ANT.
Why do we use 2 phases?
Usually if there is nodal involvement.
- You give radical dose to the PTV
- you give different doses to the primary and nodal areas (this may be due to different a/b ratios and OAR)
e.g you only need to treat the proximal seminal vesicle - not the whole thing. It also does not need as high as dose as the prostate (only needs 54Gy) . Therefore you can split the treatment into 2 phases.
What are the benefits of multi-phase planning (using more than 1 volume)?
You can increase the dose to the PTV (dose escalation)
Allows you to decrease dose to critical structures
What are the features of PTV1?
Its usually the largest volume and has lower dose.
It includes the primary PTV and nodal volumes.
Dose depend on: CRITICAL STRUCTURES and the TYPE/STAGE of disease
What can nodal volumes be classified into?
High or low risk.
This depends on proximity of the tumour, patterns of spread and whether they are positive and negative.
What are the features of PTV2?
It’s a smaller volume - does not include nodal areas.
Also called: cone down, boost volume or phase 2 volume
What are some multi-phase planning considerations.
Make sure you don’t reach the dose constraints for critical structures.
Make sure you understand that dose will contributed by phase 2 and 3
Remember that the prescription for critical structures is for the total dose not for each phase
What are some examples for multiphase plans?
Prostate 2 phase plan.
Phase 1: Prostate & Seminal vesicles 56 in 28#
Phase 2: Prostate only 18Gy in 9#
Prostate 3 phase plan:
- used for high risk prostate cancer
Phase 1: Whole pelvis 46Gy in 23#
Phase 2: Prostate and Seminal vesicles 10Gy in 5#
Phase 3: Prostate only 18Gy in 9#
Why only 46Gy for the whole pelvis?
Because of the low tolerance of the small bowel
What are the treatment planning approaches for each stratification?
Low risk: Prostate only
Intermediate risk: Prostate + SV
High risk: Whole pelvis+ Prostate and Seminal Vesicles+ Prostate only.
SIB is more efficient (using VMAT and IMRT)
What is an SIB plan
Can treat 2 or more volumes concurrently using IMRT or VMAT.
Important to consider/ work out the daily dose contributions.
What is an example of an SIB plan? (possible exam question)
Head and Neck:
PTV70 :70 Gy in 35# (2Gy per day)
PTV63: 63 Gy in 35# (1.8Gy per day)
PTV56: 56 Gy in 35# (1.6 Gy per day)
a specific example is the oropharynx.
What are advantages of SIB?
It reduces the number of fractions Head and Neck patients benefit greatly from having a shorter treatment time.
Has greater BED.
Only one plan is needed - makes QA workflow better
Increases tumour control probability
Some studies have indicated better acute side effects.
