IMRT in the US IMRT in the US Mell LK, Mehrotra AK, Mundt AJ . - - PDF document

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IMRT in the US IMRT in the US Mell LK, Mehrotra AK, Mundt AJ . - - PDF document

Oct 14, 2022 216 likes •376 views

IMRT in the US IMRT in the US Mell LK, Mehrotra AK, Mundt AJ . Cancer, 104:1296, 2005 Random sample US radiation oncologists, Summer 04 368 evaluable physicians; 239 (65%) responded IMRT usage 2002 32% 2004

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SLIDE 1

IMRT in the US

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SLIDE 2

IMRT in the US

  • Mell LK, Mehrotra AK, Mundt AJ . Cancer, 104:1296, 2005
  • Random sample US radiation oncologists, Summer ‘04
  • 368 evaluable physicians; 239 (65%) responded
  • IMRT usage

– 2002 32% – 2004 73%

  • Major reasons cited for IMRT adoption

– normal tissue sparing 88% – dose escalation 85% – economic competition 62%

  • Nonusers: 91% “planned to adopt IMRT in the future”

– The future is now in the US

  • Jan 2009: ASTRO and ACR Practice Guidelines for IMRT,

IJROBP

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SLIDE 3

Year

2002 2004 2006 2008 Approximate % Centers With IMRT Usage in US 32% 73% My guess close to 100%

2002 and 2004 data from Mell LK, Mehrotra AK, Mundt AJ . Cancer, 104:1296, 2005

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SLIDE 4

IMRT in the US

  • By site

– Nearly all: Prostate, head and neck – Many: Brain, breast – Misc:

  • GYN vs implant
  • Mesothelioma, anal. Articles on almost all site
  • Implications

– Rad Onc revenue for hospitals

  • Growth largely in Technical Revenue
  • Increases in hospital profit margin

– “Physicist employment act” – “Machine inflation”

  • Rapid adaptation of new techniques
  • Competition
  • Patient-driven

– MD: anatomy, time for segmentation – Tx times increase, longer hours, attraction of “rapid arc”

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SLIDE 5

IMRT: Misconceptions

  • “…

even with IMRT, … ‘perfect’ plan that creates completely homogeneous coverage of the target volume and zero or small dose to the adjacent organs at risk is not always

  • btained.”

(my emphasis)

  • Hatano, Int J

Clin Oncol. 12(6):408, 2007.

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SLIDE 6

IMRT: Misconceptions

  • “…

even with IMRT, … ‘perfect’ plan that creates completely homogeneous coverage of the target volume and zero or small dose to the adjacent organs at risk is not always

  • btained.”

(my emphasis)

  • Hatano, Int J

Clin Oncol. 12(6):408, 2007.

never

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SLIDE 7

Framing the Debate

  • “Anti IMRT”

– The allegation

  • Usually too complex
  • Hard to QA
  • Non-intuitive
  • Time consuming to plan,

and treat (??)

  • Expensive
  • Keep it simple
  • Distraction
  • Can’t trust it
  • “Pro” IMRT

– The response

  • Why not, it is “optimal”
  • QA will get easier with practice
  • Intuition will come over time
  • Treatment times are declining
  • Costs will drop as volume

increases

  • People said CT was unnecessary

(“we can feel and see the tumor”)

  • Don’t act so old
  • Who can you trust?
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SLIDE 8

Against IMRT Widespread Use

  • 3D relies on segmented anatomy.

– Human verification with port films

  • IMRT relies on segmented anatomy and DVH’s

– No port films – DVH’s are subject to uncertainly and human error

  • Distraction

– Move from 2D --> 3D is huge, and is far more important than all the rest (including IMRT)

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SLIDE 9

CT

Beams Apertures Contour Segment Dose Constraints

3D IMRT

Computer Computer Magic Magic

Treat

DVH Assess DVH’s Assess doses, beam

  • rientation &

aperture DVH

O.K. Not O.K. Apply prior knowledge Beam orientations, “apertures,” intensity maps not intuitive. O.K. Not O.K.

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SLIDE 10

Brain Tumor: 2 to 6 Beams

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SLIDE 11

Data from scans of patients with brain tumors

2-Beam 3-Beam 4-Beam 5-Beam 6-Beam Ź Ź Ź Ź Ź Average

  • Std. Dev.

Patient 1 2516 2649 3011 3097 3074 2870 268 (± 9.3%) Patient 2 3507 3551 3610 3739 3708 3623 100 (± 2.8%) Patient 3 4315 4420 4723 4617 4628 4541 168 (± 3.7%) Patient 4 1581 1632 1814 1780 1770 1716 102 (± 5.9%) Patient 5 4913 4980 4998 4952 4952 4959 32 (± 0.6%) Curle and Das, Duke

non-coplanar beam arrangements laterals Standard Deviations <10%

Integral Dose

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SLIDE 12

Prostate Cancer: 2 to 6 Beams

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SLIDE 13

Data from scans of patients with prostate tumors

Curle and Das, Duke 3-Beam 4-Beam 5-Beam 6-Beam Average

  • Stan. Dev.

Patient 1 8226 7593 8067 8135 8005 282 (± 3.5%) Patient 2 6911 6523 6722 6858 6753 173 (± 2.6%) Patient 3 5221 4732 5035 5145 5033 215 (± 4.3%) Patient 4 5178 4796 5099 5099 5043 169 (± 3.3%) Patient 5 4449 4198 4305 4402 4339 111 (± 2.6%)

All axial beams Standard Deviations <5%

Integral Dose

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SLIDE 14

Modified from Chapet et al. IJROBP 65:261, 2006

Mean Lung Doses (Gy): Univ. Michigan

Case 1 2 3 4 5 6 7 8

3D conformal

20.0 10.2 12.9 18.0 12.8 16.6 10.5 9.1

Same

  • rientation

IMRT

19.8 10.5 12.2 18.4 12.6 16.6 12.5 8.3

3F IMRT

20.0 10.6 11.8 18.0 13.4 16.7 12.6 9.1

5F IMRT

19.6 10.6 11.5 18.0 13.6 16.7 12.1 9.3

7F IMRT

20.1 10.6 12.4 18.1 11.2 16.6 11.0 8.9

Average

20 11 12 18 13 17 12 9

% STD Deviation 1

2 4 1 7 <1 8 4

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SLIDE 15

Deviation Rate %

3 Low Tech 1 High Tech

Years

High Tech Low Tech

4 High Tech 1 Low Tech 4 High Tech

0.16 0.22 0.20 0.11 0.09 0.10 0.06

I Increased ncreased in deviations in in deviations in “ “low tech low tech” ” txs txs: :

Maintaining ‘low tech’ competency in ‘high tech’ era