High Dose Rate Prostate Brachytherapy: Dose Escalation to Dominant Intra-prostatic Nodule (Dosepainting)

• To demonstrate the feasibility of the delivery of a higher than prescription dose to the dominant intra-prostatic nodule as defined on diffusion contrast-enhanced endo-rectal MRI, while respecting tolerance doses of adjacent normal organs. [ Time Frame: 12 months ] [ Designated as safety issue: No ]

  Data to be collected are:

  i) ratio of volume of GTV to prostate volume ii) number of DIL's per prostate iii) isodose encompassing DIL without exceeding critical organ dose constraints (Urethral volume receiving 115%= 0, Dose to 1cc of rectal wall < 7 Gy)

  
  

• To establish tolerance in terms of acute toxicity compared to a cohort of 25 patients treated to standard dose [ Time Frame: 24 months ] [ Designated as safety issue: Yes ]

  Data to be collected are:

  i) urinary retention rate and duration ii) maximum International Prostate Symptom Score and time to normalize iii) rectal toxicity

  
  
• Efficacy will be assessed by repeat DCE MRI at 12 months and TRUS-guided prostate biopsy at 30 months. [ Time Frame: 30 months ] [ Designated as safety issue: No ]
  Repeat DCE endorectal MRI will be repeated at one year post treatment to assess imaging response. Histologic response will be assessed at 30 months as studies have shown that this is the otpimal time for post radiotherapy prostate biopsy.
  
  

Radiation: HDR interstitial brachytherapy
2 treatments of 1000 cGy will be delivered to the entire prostate volume while escalating the dose to the visible disease to 1250 cGy
Other Name: Planning soft ware is supplied by Varian Medical Systems Vitesse III

Methods: If a dominant nodule is visualized on DCE MRI, it will be contoured in 3D and the images fused to the planning TRUS study that is done in preparation for brachytherapy (of any type: seeds or HDR). The patient's treatment will consist of the standard combined external beam (4600 cGray in 23 fractions) and HDR brachytherapy boost (2 fractions of 1000 cGray given on days 5 and 15 of the external beam course). During each HDR treatment the plan will be manipulated such that the normally occurring high dose regions (125%, 150%) are positioned at the site of the identified disease. Normally approximately 60% of the prostate volume receives 125% of the dose and 30% receives 150%. By ensuring that the inherent dosimetry favors treatment of the known cancer, no region of the prostate would be "underdosed". HDR treatments are performed under general anesthesia as an out patient procedure.

Statistical Analysis: This is a feasibility study and the data reported will be descriptive including the frequency with which the DIL can be visualized in this population, the DIL volume compared to total prostate volume, and the isodose that can encompass the DIL without violating dose constraints to adjacent organs (urethra and bladder). Toxicity will be monitored and efficacy will be assessed by repeat DCE MRI at 12 months and biopsy at 30 months.