Gynecological Treatment Planning

1. Gynecological Treatment Planning Patty Sponseller, CMD

2. Cervical Cancer

3. Simulation • Patient supine • Lower extremities immobilized indexed to table Table indexing documented on device

4. Simulation • Radiopaque gold seed markers at cervix and distal vaginal DZ. • No standard EBRT fields. • Block based on 3D imaging • Treat AP/PA or 4 field pelvis • Patient simulated supine with CT planning. • Rectal and vaginal marker

5. Field arrangement depends on body habitus

6. Field Borders • Superior = L4/5 • Inferior = 3 cm below gold seed most inferior involvement (often at obturator foramen) • Lateral = 2 cm lateral to pelvic brim • Posterior = Include entire sacrum • Anterior = 1 cm anterior to sym pubis

7. AP Pelvis

8. Lateral Pelvis

9. AP/PA DD

10. 4 Field Pelvis

11. Tx inguinal nodes Stage IIIA Increased Lower Border for flash

12. Common iliac nodes involved superior border to L3-4 Increase sup Border about 4cm

13. RT for para-aortic nodes Superior border T12-1

14. If conformal fields block kidneys Laterally encompass transverse processes

15. IMRT for para-aortics better to spare both kidneys and sm bowel Purple is 50% isoline

16. Doses • Doses vary with staging • From IA post hysterectomy with Brachytherapy • To IIIB-IVA WP (50-54Gy) Brachy boost and Para-aortic LN IMRT (45-60 Gy)

17. Midline Block

18. When midline block used • If 4 fld pt TX with AP/PA • Avoids excess dose to areas adjacent to implant • Reduces dose to bladder and rectum • After 54Gy boost to 60 Gy

19. Dose Calculate dose here What is the dose under the 5% transmission block?

20. Dose to point under block • Primary transmission through the block is only 5% • Dose under the block is about 20% of the dose in the open portion • Due to the internal scatter from the open field areas

21. Endometrical Cancers • Uterine Carcinomas • Leimyosarcoma, Endometrial Stromal Sarcomas • Adenosarcoma • Uterine Sarcoma

22. Simulation • Patient supine with lower extremities immobilized • Empty rectum and full bladder

23. Whole Pelvis RT Borders • Superior = L5-S1 • Inferior = below obturator canal and including upper 1/2 -2.3 vagina • Lateral = 2 cm lat pelvic brim • Posterior = split sacrum to S3 • Anterior = pubic symphysis *Consider IMRT with careful target delineation

24. Dose Prescriptions Post-op WP 1.8 Gy 45-50.4 Gy followed with VC (vaginal cuff) boost Pre-op WP 1.8 Gy to 45 Gy with T&O Paraaortic to 45-50 Gy with enlarged unresect LN boost to 60 Gy (IMRT)

25. Ovarian Cancer Simulation • Supine, lower extremity immobilization • Image entire peritoneal cavity • Treat open field AP/PA • Borders (historical) sup = above diaphragm Inf = below obturator foramen Lat = outside peritoneum RT primarily reserved for palliative DZ

26. Brachytherapy • Teletherapy (linear accelerator RT) is treatment at a distance 100 cm • Brachytherapy comes from the Greek word brachy whichmeans short • Radiation is placed near to in the tumor • High dose of radiation delivered with rapid fall off

27. Radiation used is an Isotope • Atoms having nuclei with the same # of protons and different # of neutrons • Atom decays giving off radiation

28. Brachytherapy HDR • Uses a 10 Curie source of Iriduim 192 • HL = 74.22 days • Complicated gamma spectrum ave energy .38 MeV high activity • Deliver dose in temporary placed catheters, applicators or needles placed in a patient Source embedded in a wire http://www.varian.com/us/oncology/brachytherapy/hdr_brachytherapy.html

29. HDR Treatment Unit Robot • Catheter is attached to applicator then to channel on the unit • Wire with source goes to preplanned positions in the applicator “dwell positions” to deliver correct amount of radiation • Units are made by different vendors Nucletron

30. Applicator placement • Placed with or without sedation • Depending on type of applicator • Patient then imaged on Simulator or CT sim • Plan created on TPS • Before TX applicator position then verified with conebeam or portal imaging

31. Gynecological cancers2 basic types of HDR implants Tandem and Ring Miami vaginal cylinder Tandem and Oviods (shielded colpostats)

32. Vaginal Cylinder • Deliver dose to the vaginal cuff or vaginal wall • Dose is calculated at a distance from the surface of the applicator • Not much dose to the rectum or bladder 6 Gy line

33. GOG Definitiion • Points Arepresent medial parametrium/lateral cervix, the approximate point at which the ureter and uterine artery cross. • Points B Point B is 5 cm lateral to the center of the pelvis at the same level as point A and approximates the region of the obturator nodes or lateral parametrium http://imaging.ubmmedica.com/cancernetwork/cmhb11/11_20_Fig_2.gif

34. ICRU report #38 • Rectum- 5mm posterior to posterior vaginal wall (as identified by vaginal packing) and bisecting ovoids superiorly and inferiorly • Bladder- Posterior most point of a 7cc Foley balloon (with contrast) on lateral film and bisecting on AP film

35. T&R or T&O • Dose calculated to Points “A” 2cmsup and lat to the cervical os (vaginal fornices) • Point B 3cm lateral to A approx 1/3-1/4 dose to A • Calc bladder and rectal doses or DVH • Radiopaque packing to minimize dose to bladder and rectum Dwell positons

36. Lateral T & O • Bladder and rectal Dose

37. Characteristic Dose Distribution • “Pear” shaped dose distribution • Middle portion of implant DD from tandem • Inferior DD round out to treat cervical fornices

38. Verification • Before treatment room survey • Verify correct channel to applicator • Verify CORRECT catheter length • Patient identity by 2 means • After delivery first person to enter the room carries the survey meter!

39. Before TX “Dry Run” • Before the Ir source leaves the robot housing a dummy source is sent through the applicators • This checks for any errors and patency with the catheters and verify positions http://chapter.aapm.org/GLC/media/2011/tollenaar.pdf

40. Verify your activity! A= Aoe-( 0.693t/T1/2 ) t = days since calibration of initial activity T ½ = Half life of isotope Ao = Initial activity A = Activity on you plan

41. Safety when working with Radionuclides • Keep time spent as short as possible • Increase distance away from the source (not a good idea to use the HDR delivery robot as an arm rest) • Shielding- the safest place working around the HDR unit is behind the source!

42. Reportable Errors and Medical Events • Wrong dose of more than 10% with a radioactive source • Wrong patient • Wrong source • Leaking source or non-removed source

43. National Regulatory Commission (NRC) or Agreement State • NRC sub-division of Dept of Energy • Regulates radioactive material and establishes reporting procedures • NRC and state agree to transfer authority of radioactive materials to the state called and “agreement state” • NRC then regulates only federal facilities • State regulates PET scanners, Linacs, and naturally producing and cyclotron produced radionuclides

44. States that are not agreement states Montana, Idaho, Wyoming, South Dakota, Missouri, West Virginia, Virginia, Pennsylvania, Delaware, New Jersey, Rhode Island, Vermont, Michigan, Indiana, District of Columbia, Alaska, Hawaii

45. Indiana Incident http://chapter.aapm.org/GLC/media/2011/tollenaar.pdf