Combined modality therapy with brachytherapy and external beam irradiation in the management of localized prostate cancer

The impetus to combine permanent radioactive seed implantation of the prostate gland and external beam radiation therapy (EBRT) probably derives from two main sources. The first rational for using this combined modality therapy (CMT) comes from the experience of the retropubic prostate seed implant. Since this technique of implantation was implemented prior to the use of transrectal ultrasound and computer tomography (CT)-based technology, it relied on the free hand placement of seeds with an open exposure of the prostate. This technique resulted in poor seed distribution and inadequate dose coverage. The concept of combining this technique with external beam irradiation made sense because the external beam portals could be made large enough to ensure coverage of the entire prostate and potentially make up for cold spots created with the retropubic implant. One of the first reported uses of CMT was with the open retropubic technique [1]. The second rational for using CMT probably derived from a commonly used radiation therapy technique. This technique involves the use of large external beam ports to encompass the known tumor, as well as the organ at risk, draining lymphatics, and a brachytherapy boost to the tumor, usually using a temporary radioactive source implant. This technique is commonly used to treat gynecologic malignancies and head and neck tumors. This treatment allows the tumor to receive the highest dose with contributions from both the EBRT and the brachytherapy while the peritumor surrounding tissues and draining lymphatics receive prophylactic radiation form the EBRT.