1 / 86

Aperture-based IMRT for GYN malignancies

Aperture-based IMRT for GYN malignancies. Myriam Bouchard S. Nadeau , I. Germain, P.-É. Raymond, F. Harel, F. Beaulieu, L. Beaulieu, R. Roy, L. Gingras Department of radiation oncology of L’Hotel-Dieu de Quebec, QC, Canada. Results from the dosimetric study – 2005/2006. Objectives.

ceri
Download Presentation

Aperture-based IMRT for GYN malignancies

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Aperture-based IMRT for GYN malignancies Myriam Bouchard S. Nadeau , I. Germain, P.-É. Raymond, F. Harel, F. Beaulieu, L. Beaulieu, R. Roy, L. Gingras Department of radiation oncology of L’Hotel-Dieu de Quebec, QC, Canada Results from the dosimetric study – 2005/2006

  2. Objectives • Contours definition • Target • Organs at risk • Aperture-based vs Beamlet-based IMRT • Gains vs Uncertainties in IMRT for GYN

  3. Purpose of tx Selected cases Endometrial / Uterus cervix cancer Post-operative EBRT = Local Control benefit PORTEC, Creutzberg et al. Lancet (2000) (endometrium) GOG-99 (endometrium) Sedlis Gyn Oncology (1999) (cervix) No survival benefit, attempt to reduce side effects from adjuvant treatments

  4. What do we treat? GYN postop EBRT

  5. CTV • External iliac nodes • Internal iliac nodes • Obturator nodes • Presacral region • 1/2 superior of vagina • Parameters

  6. Controversies CTV

  7. Controversies -- CTV • Endometrium CTV Þ Cervix CTV • Presacral region

  8. Presacral CTV / 4-field 95% Isodose CTV

  9. Controversies -- CTV • Endometrium CTV Þ Cervix CTV • Presacral region • Upper limit ? • L5-S1, L4-L5… (common iliac LN) • External iliac limit

  10. Ant limit / Ext. Iliac LN

  11. Controversies -- CTV • Endometrium CTV Þ Cervix CTV • Presacral region • Upper limit ? • L5-S1, L4-L5… (common iliac LN) • External iliac limit • Margin around vessels • How big?

  12. Pelvic LN mapping literature

  13. Taylor et al • 20 patients, GYN malignancies • MRI + iron oxyde particles • CTV = • margins 3-5-7-10-15 mm • PTV = CTV + 1 cm

  14. Taylor et al

  15. 99% coverage modified-7 mm Taylor et al

  16. 18 patients with prostate cancer N+ • Margin 2 cm around vessels (includes PTV) • 94,5 % N coverage

  17. Controversies -- CTV • Endometrium CTV Þ Cervix CTV • Presacral region • Upper limit ? • L5-S1, L4-L5… (common iliac LN) • External iliac limit • Margin around vessels • How big? • ITV… bladder filling • MDACC = fusion pre-postmictional CTsim

  18. ITV 1 cm

  19. + 5 mm around vessels ITV 1 cm CTV – ourinitial choices* • External iliac nodes • Internal iliac nodes • Obturator nodes • Presacral region • 1/2 superior of vagina • Parameters *Before RTOG 0418, Shih et al. and Taylor et al. publications

  20. 3D CTV

  21. PTV = CTV + 1 cm

  22. OARs • Bowel (colon + small bowel) • Region at risk to find bowel = RAR-B • Rectum • Bladder • Bone marrow

  23. Bowel / RAR-B

  24. Why IMRT for GYN ?

  25. PTV Conventional 4-fields 95% Isodose Inadequate coverage

  26. Inadequate coverage • Greer et al. (1990) • S2-3 post limit : 49% inadequate coverage • 87% com. il. bifurcation above L5-S1 • Bonin et al. / Pendelbury et al. (1993) • 45% / 62% inadequate coverage ext. il LN • Finlay et al. (2006) • 95,4% at least 1 inadequate margin with bony landmarks

  27. IMRT for GYN malignancies • Mundt et al.(Chicago, 2000)Portelance et al.(St. Louis, 2001)Heron et al.(Pittsburgh, 2003)Lujan et al.(Chicago, 2003) D’Souza et al. (Houston, 2005) Adequate target coverage OARs sparing • Small bowel • Rectum • Bladder • Bone marrow

  28. IMRT for GYN malignancies • Good clinical results with IMRT 1 • 36 patients, whole-pelvis IMRT • Median FU = 19,6 month • 13.9% less GI-GII toxicity • 3 year Pelvic LC 87,5% * (62 patients) • Cervix cancer • 71% intact uterus 1 Mundt et al. IJROBP, vol.56 #5 (2003) pp.1354-1360* Kochanski et al. ASTRO 2005 Abst #1114

  29. Disadvantages of IMRT • Target volume definition controversies • Impact of • Machine errors (MLC) • Patient positioning errors

  30. Disadvantages of IMRT • Large # of segments and MU • Scattered dose • Calculation uncertainties • Time consuming • Planning • Treatment • Quality assurance

  31. Can we improve treatment delivery issues? Ballista = Aperture-based IMRT A feasability study - dosimetric - clinic

  32. Let’s talk about IMRT Beamlet-based vs Aperture-based

  33. Forward planning(conventional) Manual (human) field definition Followed by calculation Inverse planning (IMRT) Dose objectives in specific areas (contours) Solution found by computer-assisted calculation Types of planning

  34. IMRT Intensity Modulated Radiation Therapy • Dose intensity varies inside the beam • Several sub-fields (segments) • Inverse planning

  35. Basic objectives Field geometry 1st Optimization of beam intensity profiles Segmentation Does the plan meet the clinical objectives? No Yes Final plan *** Calculation steps Beamlet-based IMRT 2nd

  36. Aperture-based IMRT

  37. Ballista1 • Inverse planning system • Recently developed at L’Hotel-Dieu de Qc • Intensity modulation • Anatomy-based MLC field • Simultaneous optimization • Gantry, table and collimator angles • Wedge angle and beam weights 1 BEAULIEU et al. Med.Phys.31, 1546-1557 (2004)

  38. Basic objectives Field geometry Aperture-based Segmentation Ballista

  39. Anatomy-based fields

  40. Basic objectives Field geometry Aperture-based Segmentation Only 1 Field weights optimization No Yes Does the plan meet the clinical objectives? Minor leaf corrections Final plan *** Calculation steps Ballista X

  41. Dosimetric study Ballista for GYN Pilot study -- Part I CHUQ -- Hotel-Dieu de Quebec Quebec city

  42. Dosimetric objectives • Evaluate Ballista as an alternative • Between 4-field and IMRT • For post-operative whole-pelvis radiotherapy in gynecologic malignancies

  43. Hypothesis • Same target coverage • Organs at risk (OARs) sparing • Better than 4-field • As good as IMRT ? • Treatment delivery advantages

  44. Materials and methods • 10 patients • Endometrial or cervix malignancies • Post-operative external radiotherapy • 45 Gy / 25 fractions, whole-pelvis + brachy HDR boost

  45. Inverse planning Materials and methods For comparison purposes 4 plans created for each patient • Conventional 4-field • Enlarged 4-field • Results for OARs at same PTV coverage • IMRT • Ballista

  46. Materials and methods Forward planning 4-field enlarged 4-field

  47. Materials and methods • Planning CTscan as usual • Conventional planning : • 4-field plans based on bony landmarks • Created before other plan conception • Enlarged 4-field • Aperture shaped to PTV

  48. Materials and methods Inverse planning IMRT Ballista

  49. IMRT • Plans created with Pinnacle3 system • Step-and-shoot • 7 coplanar and equidistant 6 MV beams • 1 extraction • 10-12 intensity levels • Minimum field area = 4 cm2

  50. Beam orientation for Ballista plans 9 beams 23 MV

More Related