Contouring Guidelines for Gynecological Malignancy
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Contouring Guidelines for Gynecological Malignancy

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A brief overview of gynecological malignancy contouring guidelines (teletherapy & brachytherapy), including a discussion of problems and inadequacies of the present guidelines

A brief overview of gynecological malignancy contouring guidelines (teletherapy & brachytherapy), including a discussion of problems and inadequacies of the present guidelines

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Contouring Guidelines for Gynecological Malignancy Contouring Guidelines for Gynecological Malignancy Presentation Transcript

  •  For image-based conformal planning, targets and OARs have to be delineated for optimal treatment As we move from 4-field box arrangements and point A-based dose prescriptions, good imaging modalities and protocols become necessary
  •  Even though most guidelines are based on MR, in practice, it is prohibitively expensive to do routine MR-based planning TPSs too, have only recently become capable of dose calculation on MR & even now, there is no commercially available MR-based TPS
  •  The GTV itself may/ may not be well seen The parametrial disease is usually not visualised MR-based guidelines for parametrial contouring are confusing Though pelvic nodal contouring is systematic, but we still tend to end up replicating the traditional cranio-caudal boundaries of a 4-field box
  • CT MR
  • Uninvolved parametria: Clear fat plane visible between cervix and parametriumParametrial invasion: No fat plane visiblebetween cervix and parametrium
  •  The RTOG guidelines for pelvic LN contouring are well-described CTV nodes should include the : common iliac, external iliac, internal iliac, obturator and presacral groups
  • (1) Draw the pelvic vessels (4) The presacral space (tightly) and grow 7mm- coverage is crucial, at least 1cm margins around upto the S2-S3 junction. The them=nodal CTV. ** thickness of the CTV should**Based on Taylor et al’s work be at least 1-1.4cm in the with USPIO:7mm margins midline. Normally this part around the pelvic vessels of the CTV is taken till the cranial-most slice in which were found to the rectum becomes visible encompass 95% of the nodes. (5) The external iliac nodes should be drawn till the(2) Do not include the ilio- slice where the heads of psoas & piriformis muscle the femurs become visible bellies within the CTV. (6) The internal iliac nodes(3) The nodal CTV upper should be included below border should reach upto this level till the uppermost 7mm-1cm caudal to the slice where the symphysis L4-L5 junction pubis becomes visible
  • Common Iliac nodesPre-Sacral nodes
  • External & Internal Iliac nodes
  • TMH protocol: Draw the GTV (based on clinical and imaging findings). Grow margin of 0.5-1cm all around (edited from rectum and bladder). Join with the vagina & uterine body (without margin) Vagina should be included at least till the bottom of the ischial tuberosity. If there was lower vaginal disease, it is best to include up till the introitus. The weakness of this protocol is that the parametrium disease may not be adequately covered, especially in IIIB disease.
  •  Most clinicians agree on including the entire corpus uteri in the CTV primary At least the upper ½ of the vagina needs to be included in the CTV primary (in the absence of vaginal involvement) In case of vaginal involvement, upper 2/3 of vagina needs to be included Entire vagina should be included for extensive vaginal involvement
  • What to delineate for IIIB disease?
  •  Join the CTV nodes & CTV primary by Boolean function=CTV pelvis Now apply a margin of 0.7-1.5cm (cranio-caudal) and 0.7-1cm (radial) over CTV pelvis= PTV pelvis Ideally, the PTV margin should be individualised, for the centre, the immobilisation system and the particular patient
  • Common Iliac Pre-Sacral
  • PresacralExternal & Internal iliac External & Internal iliac
  • Presacral ParavaginalExternal & Internal iliacs External & Internal Iliacs
  • Vagina & Paravaginal Tissues Vagina
  •  Hypointense areas on T2 weighted MRI + Entire cervix + Parametrial/vaginal disease (if present)
  •  Hypointense areas on T2-weighted MRI + Entire cervix + Parametrial/vaginal disease (if present)
  • Includes: GTVB + All gray zones (areas of high-signal intensity on MR)
  • Includes: GTVD + 1cm margin craniocaudal & lateral, 5mm AP(edited from bladder and rectum)
  •  Urinary bladder Rectum (rectosigmoid junction to anus) Sigmoid colon Small bowel (loops vs space) Femoral heads
  •  If doses to small volumes (2cc) are to be measured, it doesn’t matter, as the high dose volume is located mostly in the wall anyway
  •  Summing dose  The BEST fusion is the one in distributions between your head: clinical EBRT and findings, teletherapy & brachytherapy is not brachytherapy contours possible with most TPS and distributions are most (as the data sets are meaningful this way! different: patient This is why, for positioning demands  this) brachytherapy, post- insertion MR and MR- MR-CT fusion on the compatible applicators are TPS for such mobile not compulsory structures will also have an inherent error  A pre-EBRT and pre-BT MR can be sufficient the data is extrapolated on the CT scans