IMRT for Breast Cancer

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• IMRT for Breast Cancer

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Everybody benefits from better planning

• 3D conformal treatment is better than simulated
  tangents
• Better dose uniformity
• The side effects are dependent on certain areas
  receiving much higher doses
• IMRT breast technique does have clear advantages
  when IM nodes are irradiated
• Potential role for partial breast radiotherapy
• The contralateral breast dose increases
  significantly

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Problems with breast radiotherapy
The chest is even more moving target than the
prostate
Larry Kestin, ASTRO presentation 2005
The breast hold technique is probably more
important is sparing the lung and heart
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Forward planned IMRT

• Its probably not exactly IMRT in the real sense
• Does not use inverse planning
• Sophisticated way of achieving multiple
  intensity levels
• The beams do have 2 predeterminate 180 degree
  apart angles
• Tangents
• The contour of PTV is usually relatively
• Simple
• Not really concave
• Simple to implement technique
• Does not need specific plan verification

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Forward planned IMRT
Start with open field tangents Prescribed 50Gy in
25 fractions
5500
5250
4750
5000
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Relative dose distribution
Simple wedging with central slice would not
account for upper and lower cold and hot spot
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Better homogeneity
decrease the dose with 10
decrease the dose with 5
increase the dose with 5
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Prepare MLC segments 90of the dose
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First segment
Cover the hottest spot 110 Deliver 5 of the
total dose
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Second segment
Cover the second hottest area 105 Deliver 5 of
the total dose
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Third segment
Cover the next dose area 100 Deliver 5 of the
total dose to 95 area
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3D Forward planned IMRT vs Single slice RT
extra breast tissue identified
Tangents 2D
Tangents 3D
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Potential problems

• We have never really irradiated the whole breast
  with simulator based techniques
• Outlining the whole breast leads to
• More lung in the radiotherapy field
• Higher dose to the superior aspect of the breast
• IMRT may lead to
• Higher integral dose
• More dose to the contralateral breast
• More breast swelling
• More lung fibrosis
• IMRT on its own does no treat less heart (without
  resp. gating)

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Breast IMRT - Summary

• Multisegment tangents is probably everything one
  needs
• Full multiangle IMRT is possible but probably not
  necessary
• Some potential problems with dose in build up
  region
• Most of the benefit will come from breath holding
  techniques
• The jury is still out
• less is more (partial breast radiotherapy)
• more is more (comprehensive chest irradiation
  based of British Columbia and Dutch studies)

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• This presentation is done with close co-operation
  with