1. Morbidity / Complications
Patients experienced only expected post-implant reactions
Two patients with self-limited superficial necrosis of vaginal mucosa
No hospitalizations, fistulas or other severe side effects
Wooten CE, Randall ME, … Feddock J. Implementation and Early Clinical Results utilizing Cs-131 permanent interstitial implants for gynecologic malignancies. Gyn Oncol 2014.

2. WHAT IF THERE WERE A TREATMENT FOR RECURRENT GYNECOLOGIC CANCERS WITH:
A SIGNIFICANT SALVAGE RATE (CURE), and
LIMITED MORBIDITY, and
AT A REASONABLY LOW COST?
THERE IS SUCH A TREATMENT FOR SELECTED
PATIENTS: INTERSTITIAL RE-IRRADIATION.
DON’T FORGET ABOUT IT!

3. Use of Cesium-131 in Definitive Therapy for Gynecologic Malignancies
Primarily used as a boost:
Adjuvantly for a positive margin (vaginal cuff post hysterectomy)
Definitively to treat gross disease
Unresectable disease
Small volume residual following standard therapy
Ideally reserved for patients considered unsuitable for treatment using Syed-Neblett either for medical or logistical reasons

4. UK Experience using Cs-131 as a component of primary therapy
Median age: 66 (37-87)
Type of Cancer N=
Recurrent Endometrioid AdenoCa 5
Post-operative Endometrioid AdenoCa 4
Post-operative Cervical SCCa 2
Primary Vaginal AdenoCa 3
Vaginal Melanoma
Vulvar SCCa

5. Characteristics of Cs-131 Implants used for Primary Therapy
Total implants performed: 18
Median dose = 22 Gy (15-50 Gy)
Median seed count = 13 (9-30)
Median source strength = 0.76 u/seed ( )
Median area treated = 6 cm2 ( cm2)
Indication for Cesium-131 Boost N=
Microscopic positive margin 4
Gross disease post-operatively 2
Gross disease at end of primary radiation 10
Gross disease before primary radiation (melanoma)

6. Results incorporating Cesium-131 into Initial Therapy
Median Follow-up 6.7 months ( months)
Disease control:
There have been no local failures – LC = 100%
Only one patient has developed regional and/or metastatic disease
Patient with vaginal melanoma developed a confirmed inguinal lymph node recurrence at 8.2 months post treatment
Toxicity:
Very low – nearly all develop acute grade 1-2 mucosal reactions that quickly resolve
Two patients have developed grade 3 mucosal reactions
One with persistent changes beyond 6 months
One patient has identified persistent grade 2 GU toxicity beyond 6 months

7. A Case of Vulvovaginal Melanoma
40 Gy to 5mm using Cs-131
2 weeks later
Additional 30 Gy using EBRT

8. What can be gained by adding Interstitial Brachytherapy?
45 Gy PRT followed by ICB 7 Gy to 5mm depth x3
45 Gy PRT followed by ICB 7 Gy to surface x2 then 20 Gy Cs-131
Dose to 5mm Depth
BED = 88.8 Gy
EQD23 = 74.0 Gy
Dose to Vaginal Surface
BED = Gy
EQD23 = 87.0 Gy
Dose to the Rectum (approx 5mm deep)
EQD210 = 85.2 Gy
7 Gy per implant delivered to the entire active length treated
Dose to 5mm Depth
BED = 88.8 Gy
EQD23 = 73.0 Gy
Dose to Vaginal Surface
BED = 97.4 Gy
EQD23 = 81.1 Gy
Dose to the Rectum (approx 5mm deep)
EQD210 = 70.2 Gy
Gy per implant times active length
Receives prescription dose of Cs-131 implant, but to length of 1-1.5cm
All calculations performed using GEC-ESTRO LQ Worksheet.

9. Patient Selection How do we decide which type of implant to use?
Depth of the tumor
< 5mm: vaginal cylinder will do fine
5mm – 1cm: permanent implant using Cesium-131 or Gold-198
≥ 1cm: Syed-Neblett or other catheter based treatment
Vaginal Cylinder
Permanent Seeds
Syed-Neblett

10. Conclusions
UK first to utilize/investigate Cs131 permanent interstitial implants for recurrent or new primary gynecologic malignancies.
Actuarial local control rate at time of analysis was 84.4%, exceeding other published rates with minimal toxicity.
Interstitial implants with Cs-131 should be more frequently and widely incorporated into management of gynecologic malignancies, including accessible recurrences following previous RT.

11. So How Do I Perform One?
42 year old female diagnosed with Stage II clear cell uterine cancer after TAH/BSO/LNS
Receives adjuvant therapy:
45 Gy to the Pelvis followed by 6 cycles of Carbo/Taxol
Within first month off therapy develops vaginal bleeding
Biopsy proven recurrence at vaginal apex
Treated with Vaginal brachytherapy 30Gy/10 fractions BID to the surface
3 weeks post brachytherapy, exam demonstrates progressive tumor at the vaginal apex
MRI confirms this is only site of disease
Scheduled for Exenteration with Gyn Oncologist
Treated instead with Interstitial Re-irradiation using Cesium-131

12. 2.5cm
4cm

13. Description of Procedure
Gross tumor volume to be implanted determined based on three-dimensional tumor measurements based on pelvic exam and imaging
Total activity, seed strength, and geometry calculated using Paterson-Parker rules
Outpatient procedure in the Radiation Oncology Department
Premedication: 5-10 mg po Diazepam
Local anesthesia: 2% lidocaine ± epinephrine
Individual seed applicators to insert each seed

14. Plan to deliver 55 Gy to 3 x 4.5cm ellipse 3cmB
4.5cm
1. Determine the Area: π * A * B = π * 1.5 * 2.25 = 10.6 cm
2. Determine the necessary activity to deliver 10 Gy in Radium equivalent

15. 3. Convert the activity in Radium equivalent to activity in Au-198:
8.25 R-cm2/mg-hr * 250 mg-hrs * 55 Gy = mCi of Au-198
2.38 R-cm2/mg-hr mg-hrs Gy
4. Convert the activity in Au-198 into activity in Cs-131 using conversion factor of 1.1:
51.09 mCi of Au-198 * 1.1 = mCi of Cs-131
5. Determine the number of seeds necessary to perform the implant:
Using Paterson-Parker Rules
Area <25 cm2 2/3 in the peripheral, 1/3 central
Circumference = cm
Spacing seeds evenly at 1cm increments – 12 seeds will be needed
If 2/3 = 12, then 1/3 will equal 6
So total number of seeds = 18

16. 6. Determine the activity needed per seed:
Total activity = mCi of Cs-131 = 3.12 mCi/seed
Seed count 18 seeds
Convert to Air-Kerma Strength using factor of 0.638:
Air-Kerma Strength = 3.12 mCi/seed * u/mCi = 1.99 u/seed
So, we need to order 18 seeds at 1.99 u/seed to deliver 55 Gy to 5mm depth
I usually order 10% extra in order to account for tumor growth between calculation and implant date
So we ordered #21 seeds