March 27, 2018
Discuss CB-CHOP (by Mary Dean in Applied Radiation Ooncology Dec 2017) as a simple way to evaluate a plan.
Goal is to be systematic in the evaluation so that you don’t miss things.
Heterogeneity/Hot and cold spots
Case 1: Intact Cervix: 4 field and IMRT comparison
64 year old with RLQ pain for 1 year and 6 weeks of post-menopausal bleeding found to have a 6 cm mass in the cervix, FIGO IIB, left PM involvement, SCC of the cervix.
Contours: UteroCervix – entire uterus is included in CTV
For IMRT have to think more about PTV margins – at the uterus is a mobile structure
Beams: With 4 field box need to make sure entire CTV is included, cover entire sacrum for the uterosacral ligament and pre-sacral nodes.
Tools to use:
Qualitative: Isodose lines
Quantitative: Dose statistics + DVH
DVHs: Limitations – no spatial information (where hot/cold spots are)
Discuss PTV Coverage – difference in conformity and heterogeneity with 3DCRT vs. IMRT
Heterogeneity: Hot spots + Cold spots
For IMRT remember:
If priority is conformity – accept increased inhomogeneity
If priority is homogeneity – accept decreased conformity
Questions to think about:
- What level of coverage is acceptable?
- What amount of hot spot is acceptable?
- What are your goals? What can you compromise on/what is not flexible?
OARs: Parallel vs. Serial structures, make sure constraints are relevant to the lower doses used in gyn planning (as opposed to prostate)
Prescription: Usually 45Gy to the whole pelvis. Need to consider central dose when planning to add brachytherapy. Doses can be tracked in the ABS brachytherapy worksheet.
Case 2: Uterine Postop: IMRT
63 year old with FIGO grade 1 stage IB endometrioid adenocarcinom s/p TAHBSO with deep invasion of the myometrium and LVSI.
Contours: ITV for vaginal cuff: how it is created, full bladder scan used for treatment planning and daily treatment. Patients need bladder filling instructions to make consistent.
Beams: Assess beam angles. How can you tell if a plan is with static IMRT vs. Arcs. Assess beam entrance paths and ensure not through OARs.
Coverage: Similar to prior case.
Heterogeneity: Similar to prior cases.
OARs: Great reference for constraints RTOG 1203. Consider adding bone marrow if giving concurrent chemotherapy.
Prescription: Usually 45-50.4Gy
Discussion: IMRT may not be feasible in women who cannot hold full bladder, are morbidly obese, or need to start treatment quickly.
Case 3: Uterine postop: 4 field
83 year old with FIGO IIIA grade 2 endometriod adenocarcinoma s/p TAH BSO on RTOG 1203 and received 45 Gy in 25 fractions.
Contours: splitting sacrum on lateral field.
In post op setting with no uterus, bladder filling becomes even more important as bowel fills the space.
OARs: Bladder and rectum get the entire dose but can adjust this and use constraints with IMRT per RTOG 1203 constraints (as above).
60 year old with vaginal discharge with FIGO IIB) left PM involvement SCC of the cervix.
- looking at placement with xray or fluoroscopy
- -Point A and B
- Dosimetry and coverage
- Benefits and pitfalls of inverse planning
- D2cc and adding doses with EBRT on excel spreadsheet
65 year old with FIGO grade 1 stage IB (10/12mm MMI with no LVSI) endometriod adenocarcinoma s/p TAH-BSO and SLN.
- Dosimetry, prescribing to 5mm depth vs. surface
- Coverage and constraints
- Syed Template
81 year old with a history of hysterectomy who had 2-3 months of vagina discharge and bleeding found to have SCC of the vagina involving the paravaginal extension without side wall extension, FIGO II.
- Discussion of syed template and when to use
- Show MRI for pre plan and what to cover