Monday, February 16, 2009

Brachytherapy Rounds - Sarcoma Implant + Syed Template

Brachytherapy Rounds today covered implants for a sarcoma and a Syed template for vaginal cancer.

Case 1 (High Grade Sarcoma): The sarcoma was a large (24cm in greatest dimension) high grade sarcoma of the R thigh.  The mass was invading skin.  Biopsy confirmed prior to treatment.  He was planned to be treated preoperatively with 50Gy on the IGRT RTOG protocol for sarcomas.  Unfortunately during his external beam treatment had a bleed from his tumor at 32Gy, requiring urgent surgical intervention.

Intraoperatively catheters were placed so that his RT could be completed via HDR. 24 catheters were placed 1cm apart, transversly across the tumor bed.  Catheters extended to the skin on both sides and were tacked down in both the bed and on the skin.  Wound was covered with a wound vac - uncertain to date wether this will heal by secondary intention or by graft at some later date.

Margins on the resection were negative.

HDR dosing was 4Gy x 4 BID prescribed to 1cm in tissue.  Treatment was delayed till 1 week after resection.

Case 2 (Vaginal Adenocarcinoma): Pt with an adenocarcinoma of the RV septum.  Presented with postmenopausal bleeding in 5/2009.  Hx of fibroids, treated with TAHBSO in 2004.  Speculum exam was limited by mass effect in the vaginal and rectum.  EUS was performed revealing tumor extending 10cm along the RV septum extending distally just prior to the introitus.  Biopsy was positive for poorly differentiated adenocarcinoma.

There was a debate at to wether this was a vaginal primary vs. a rectal primary.  Per clinical exam and pathologic review, this was finally characterized as a vaginal primary.

Patient was thought to have a high risk of rectal obstruction during treatment and a diverting colostomy prior to initiation of treatment.  Treated with external beam RT - WPRT with concurrent cisplatin to 50.4Gy.  Pt was initially treated with APPA fields covering the inguinal/pelivic nodes and primary for 10 fx, and was then converted to IMRT to complete treatment.  Pt had a minimal response upon treatment completion.

Pt was then brought in for interstitial implant.  Preplanning was based on pretreatment imaging.  It is important to order the strands in advance and pre-plan placement of the catheters so that one can be ready on the date of implant.

On Date of implant
1. EUA is performed and gold seeds are placed at the proximal, distal and lateral extents of disease.  
2. Cylinder and and template are placed to get a gauge to how far the cylinder can be placed within the vaginal.  This was marked on the cylinder for reference.
3. Clinically it was determined that the catheters should extend 2cm beyond the cylinder.  A sample catheter was placed with the template on the OR table to measure how far from the hub of each catheter should be from the template surface.  (much further than this, one must consider having laparascopic confirmation that the catheters are not entering the peritoneal cavity)
3. 24 catheters were placed posteriorly along the RV septum, and around the cylinder.  After we were happy with the placment the trochars were removed.
4. Patient was brought for CT, and simulator confirmation of placement.
5. Rx was to the 50cGY/hour IDL x 50 hours planned

Unfortunately patient pulled the entire implant out at approximately 36hours.  Uncertain what happened at the time, appartently the patient recieved ativan and became disoriented.  Regardless, the implant was placed in the pig, and the room and patient was surveyed to ensure that all activity was in pig.

Plan is going to be to try to reconstruct the dose delivered and will boost with IMRT afterwards.

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