1. IGRT in Head and
Neck Cancer
{
Avraham Eisbruch
University of Michigan

2. Two goals for IGRT
 1. Assess and correct set-up
uncertainties using imaging:
 2D imaging or CT
 2. Assess and correct changes in
tumors and critical organs during
the course of therapy:
 CT

3. Using 2D imaging for set-up corrections

4. {

5. {

6. {

7. {

8. Cone-beam CT-based : Correction for setup
(Translate only based on C2)

9. Cone-beam CT-based : Correction for setup
(Translate only based on C2)
Correction for setup
(Translate only based on C2)

10. How often should we image to minimize set-up deviations?
Zeidan OA et al, IJROBP 67:670, 2007
Imaging every day if PTV margins are 3 mm, every other day if 5 mm

11. How should we image? CBCT vs 2D portal imaging
The differences are mostly within 0-2 mm.
Wu QJ et al, IJROBP 2007
The frequency of imaging is more important than the mode of imaging

12. How can we correct rotational errors?

13. Correcting rotational
errors
1. Re-positioning and re-making
the mask
2. re-planning on the new
rotated position
3. Correct the rotation using a
rotating couch

14. IJROBP 2007

15. Barker et al. IJROBP 59(4) 2004

16. Registration

17. Registration accuracy

18. Planning Fraction 3
CT Fraction 8
Fraction 13 Fraction 18 Fraction 23

21. GTV change over time
Barker et al. IJROBP 59(4) 2004

22. L.N. change over time
Barker et al. IJROBP 59(4) 2004

23. PTV70 : Max<77Gy, Min>70Gy
80
Max(1%)
75
70 EUD
65
Min(1%)
Gy
60
55
50
45
40
0 5 10 15 20 25 30 35
Fx#

24. PTV59: Max<69Gy, Min>59Gy
80
75
70
Max(1%)
65
EUD
Gy
60
55
Min(1%)
50
45
40
0 5 10 15 20 25 30 35
Fx#

25. Tumor shrinkage during RT
Median 70% GTV loss at the completion of therapy
Barker et al, IJROBP ’04;
Should we modify the treatment plan during RT?
Mohan et al, IJROBP 2005

26. fx0 fx35

30. Building a cumulative actually delivered dose
map
 Need to outline each target and organ on each
during-treatment CT in order to calculate the
doses each day, then to combine all doses to
achieve cumulated DVHs.
 Outlining the targets and organs manually on
each CT is not practical

31. Deformable Registration

33. Dose Accumulation Using Deformable
Registration

34. Dose Accumulation Using Deformable
Registration

35. Difference between Planned and Delivered Mean Parotid
Dose: University of Michigan
10.00
8.00
6.00
4.00
2.00
0.00
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
-2.00
-4.00
-6.00
Hunter et al, ASTRO 2012

36. Re-assessment of parotid doses during IMRT (no re-planning)
The dose changes are higher in patients losing wt
Robar JL, et al, IJROBP 2007

37. Patient Lost 35 lbs
Planning CT Weekly DTD Plan on generated CT35

38. Decrease Parotid Volume and
Increased Mean Parotid Dose
100
90
Red= Planned Left Parotid
Green = Planned Right Partoid
Mean Dose to Left
80 Blue = Accumulated Left Parotid
Orange = Accumulated Right Parotid
Parotid increased by
70
2.3 Gy with 26%
decrease in volume.
60
Volume (%)
Mean Dose to Right
50
Parotid increased by
40 6.1 Gy with 40%
decrease in volume.
30
20
10
0
0 10 20 30 40 50 60 70 80
Dose (Gy)

39. Anatomy Change Without Dose Change
{

40. Dose Gradient Effect
Planning CT Weekly DTD Plan on generated CT35

41. Patient Lost 41 lbs.
100
90
 Mean Dose to Left
80 Parotid increased by
70 1.6 Gy with 32%
decrease in volume.
60
Volume (%)
50
 Mean Dose to Right
40
Parotid decreased by
30 0.6 Gy with 24%
20
decrease in volume.
Red= Planned Left Parotid
Green = Planned Right Partoid
10 Blue = Accumulated Left Parotid
Orange = Accumulated Right Parotid
0
0 10 20 30 40 50 60 70 80
Dose (Gy)

42. Dose Change
without Anatomy
Change
{

43. 100
Red= Planned Left Parotid
Green = Planned Right Partoid
90 Blue = Accumulated Left Parotid
Orange = Accumulated Right Parotid
 Mean Dose to
80
Left Parotid
70 increased by 7.1
60
Gy with 3%
decrease in
Volume (%)
50 volume.
40
30
 Mean Dose to
Right Parotid
20 decreased by 1.2
10
Gy with 6%
decrease in
0
volume.
0 10 20 30 40 50 60 70 80
Dose (Gy)

44. Alignment to the posterior body of C2 using
CBCT

45. The effect of rotations on
parotid gland doses

46. DVH without rotation
100
Red= Planned Left Parotid
Green = Planned Right Partoid
90 Blue = Accumulated Left Parotid
Orange = Accumulated Right Parotid
80
70
60
Volume (%)
50
40
30
20
10
0
0 10 20 30 40 50 60 70 80
Dose (Gy)

47. Selective parotid flow measurements pre and
Post-RT

48. Saliva output vs mean doses to the parotid glands:
Saliva vs planned dose and saliva vs actually delivered doses
Saliva flow by dose administered at month 6
1.6
1.5
Planned Dose
1.4
1.3
Delivered Dose
1.2
Stimulated Saliva Flow (ml/min)
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
20 30 40 50 60 70
Mean Dose (Gy)
Hunter K et al, ASTRO 2012

49. High correlation between dose deviations in the first treatment
and the cumulative dose deviations
10
(delivered – planned) dose on first day of treatment
8 Correlation = 0.92(<0.001)
6
4
2
0
-2
-4
-6
-8
-10
-10 -8 -6 -4 -2 0 2 4 6 8 10
(delivered – planned) dose for the entire treatment
The main reason for the deviations: rotations

50. Conclusions
 Rotations can be a significant factor in the
difference between planned dose and actual
dose received.
 Managing rotations by robust planning
and/or rapid monitoring and correction may
reduce parotid toxicity with minimal impact
on plan quality

51. Tumor shrinkage during
RT
 Should we re-draw the GTV
and re-plan for a smaller PTV?

52. Neoadjuvant chemo: Its tumor effect is trivial even if clinical CR
is achieved.
Similar effect is likely at mid-course of RT even if tumor
shrank according to re-CT.
OR: partial RT course
After Ian Tannock

53. Adaptive Therapy?
Changes in mass and position of the parotid glands during RT
Medial shift of the parotid, correlates with wt loss:
Higher doses than planned are actually delivered
Barker et al, IJROBP 2004
Reduce weight loss during RT!

55. Who may need re-
planning?
 Patients with shrinkage of bulky tumors
 Patients with significant weight reduction
 Both lose mask fitting in addition to
anatomical changes
For other patients: The benefits of
re-planning need more study