Advanced Treatment Strategies in Brachytherapy

Patient: 71-year-old female Diagnosis: Distal Rectal Cancer
Rx: 5 Gy QWK x 3 delivered via single-entry, multi-catheter applicator
Challenges: Maintaining safe dose limits to critical structures in patient with recurrent rectal cancer previously treated with EBRT.

The patient, a 71 year old female was found to have a low lying rectal cancer initially treated with chemotherapy but was not a candidate for pelvic radiotherapy due to previous radiotherapy for cervical cancer in the 1970’s. As an alternative to an abdominoperineal resection, endoluminal high-dose brachytherapy was chosen.

The patient was enrolled in an IRB-approved dose escalation protocol using the AR-1, an 8 channel single use brachytherapy applicator. The dual balloon construction features a compliant outer balloon designed to conform around a firm, exophytic rectal mass leading to dose escalation to the tumor while sparing normal rectal tissue.

Under general anesthesia, 3 gold fiducial markers were implanted in the rectum, 2 distal and 1 proximal to the tumor (Figure 1). The AR-1 was placed in the rectum and a 3T-MRI based treatment plan (Figure 2) was prepared to deliver 15 Gy over 3 weekly fractions to the target volume while sparing healthy rectum, bladder, bowel and anal muscle (Figure 3).

Prior to each treatment, CBCT/Fluoroscopy was used to place the applicator in the treatment position and confirm the treatment geometry using rigid registration of the CBCT and planning MRI. After registration of the applicator images, positioning was evaluated based on the match of the gold markers.

The treatment plan yielded the following data:

Comments and images courtesy of Karyn A. Goodman, MD and Gil’ad N.

Cohen, MS Memorial Sloan Kettering Cancer Center New York, NY