Reduction of treatment volume and radiation doses to surrounding tissues with intraprostatic gold markers in prostate cancer radiotherapy.

Background: High-precision radiotherapy with gold marker implantation is a standard technique for prostate cancer treatment. To provide insight into the beneficial effect of gold markers, the influence on treatment volume and radiation doses to healthy tissues was investigated.

Patients And Methods: Three consecutive treatment margins were constructed, for 10 patients with localized prostate cancer, to show the reduction of planning target volume (PTV): PTV 10 mm (no markers), PTV 7 mm (markers), and PTV 7/5 mm (markers and online correction). On planning computed tomography (CT) scan, the prostate, bladder, rectal wall, and anal canal were contoured. The treatment volume and radiation doses to surrounding organs were calculated. In 65 patients, with the online protocol and gold markers, late toxicity was evaluated.

Results: With gold markers a significant PTV reduction of 27% was achieved (P < .001). Subsequently, radiation dose reductions to the mean of 17% (± 4.5%) to the bladder, 19% (± 4.7%) to the anal canal, and 12% (± 3%) to the rectal wall, respectively were seen (P < .001). With 5-mm posterior margins an additional PTV reduction of 3.7% (P < .001) and total radiation dose reduction to the mean of 24% (± 4%), and 16% (± 4.5%) to anal canal and rectal wall, respectively were seen (P < .001). Late Grade 1-2 genitourinary and gastrointestinal toxicity was seen in 32%, and 33%, respectively. Grade 3 toxicity was less than 10%.

Conclusions: This study showed a significant reduction of treatment volume and radiation doses to healthy tissues with intraprostatic gold markers.