Intensity-modulated radiotherapy for a prostate patient with a metal prosthesis

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Treating prostate cancer with metallic prostheses using 3D conformal radiotherapy (3DCRT) often involves limited radiation fields to avoid the prosthesis.
• This limitation can compromise the dose sparing of nearby organs like the bladder and rectum.

Purpose of the Study:

• To investigate the feasibility and efficacy of intensity-modulated radiotherapy (IMRT) for prostate cancer patients with metallic prostheses.
• To compare IMRT with 3DCRT in terms of dose sparing for the bladder and rectum.

Main Methods:

• Three prostate cancer patients with metallic prostheses were studied.
• Treatment plans were generated using both 3DCRT (5 fields, 18-MV) and IMRT (9 fields, 6-MV), with all fields avoiding the prosthesis.
• Clinical target volumes (CTV), bladder, and rectum were delineated on CT scans; planning target volumes (PTV) were created with a 1-cm expansion.

Main Results:

• IMRT plans demonstrated superior sparing of the bladder and rectum compared to 3DCRT plans.
• The volume of the bladder receiving 80% or greater dose decreased by 20-77 cc with IMRT.
• The volume of the rectum receiving 80% or greater dose decreased by 24-40 cc with IMRT.
• A drawback of IMRT was target dose homogeneity, ranging from 95% to 115%.

Conclusions:

• IMRT is a feasible and effective technique for improving bladder and rectal dose sparing in prostate cancer patients with metallic prostheses.
• While IMRT offers significant advantages in organ-at-risk sparing, attention to target dose homogeneity is necessary for optimal treatment outcomes.