A color-wash representation of an IG-IMRT  plan for post-seeding radiation, treating only the periprostatic lymph nodes on either side of the prostate. The area of high dose (in red) corresponds tightly to the area being treated.

The 41Gy dose was initially chosen since early physics and radiobiologic evaluations performed by physicists at Memorial Sloan Kettering (MSKCC), especially Dr. Lowell Anderson, suggested that this dose given along with an attenuated dose of palladium-103 of 8000-9000cGy would not exceed rectal, urethral or bladder tolerances. Bear in mind that in the latter 1980's, no one knew the correct doses when combining EBRT + Pd-103. At that time, the Pd-103 isotope was relatively new and Dr. Anderson was instrumental in characterizing the physical parameters and laid the groundwork for clinical models.

Dr. Dattoli worked closely with Dr. Anderson and other physicists at MSKCC and adopted these dose parameters, and has since, never had an incidence of rectal fistula or urethral-rectal fistula. The dose of 41Gy, however, is insufficient in most cases to eradicate microscopic, and especially potentially macroscopic cancer cells, at a distance from the prostate gland. For this reason, following the implant procedure, our physics/dosimetry staff then generates precise isodose curves eminating from the seed implant (both inside and outside the gland).

The dose projected by the seeds to a given distance from the prostate can then be precisely calculated up to the point of near complete decay of the palladium 103 at the three month mark status post seeding. For this reason, most patients return approximately three months status post seeding (at the point of near decay of the isotope) to receive additional treatments to peripheral target tissue sites while blocking the prostate, bladder, rectum, and proximal penile tissues.

The individualization of the dose is multifactorial which may include taking into account the size of the gland, stage, size of tumor(s), location of tumor(s), Gleason score, PSA, PAP, prior TURP/TUIP, etc. The optimal dose to target points at distance from the gland, and the subsequent physics analysis will determine the number of treatments necessary to achieve the desired dose. It is to be noted that this methodology has been in place since the mid 1990's, although, is now more liberally utilized with IMRT in view of the safety associated with dose escalation using this newer modality.