PURPOSE: To investigate the optimal distribution of sources using high dose rate brachytherapy to deliver a focal boost to a dominant lesion within the whole prostate gland based on multi-parametric magnetic resonance imaging (mpMRI).
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METHODS: Sixteen patients with prostate cancer underwent mpMRI each of which demonstrated a dominant lesion. There were single lesions in 6 patients, two lesions in 4 and 3 lesions in 6 patients. Two dosimetric models and parameters were compared in each case. The first model used 10mm intervals between needles, and the second model used additional needles at 5mm intervals between each needle in the boost area.
RESULTS: Three of thirty-two plans did not achieve the plan objectives. These three plans were in the first model. A higher median urethral volume was seen in the 'unsuccessful' group (2.7cc, and 1.9cc, respectively, p-value=0.12). Conformity indices of the second model were also better than the first model (COIN index; 0.716 and 0.643, respectively).
CONCLUSIONS: Focal monotherapy based on mpMRI achieves optimal dosimetry by individualizing the needle positions using 5mm spacing rather than 10mm spacing within the boost volume. A larger urethral volume may have an adverse effect on this distribution. Formal clinical evaluation of this approach is currently underway.
Dankulchai P, Alonzi R, Lowe GJ, Burnley J, Padhani AR, Hoskin PJ. Are you the author?
Mount Vernon Cancer Centre, Northwood, United Kingdom; Division of Radiation Oncology, Department of Radiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand; Mount Vernon Cancer Centre, Northwood, United Kingdom; Paul Strickland Scanner Centre, Mount Vernon Cancer Centre, Northwood, United Kingdom.
Reference: Radiother Oncol. 2014 Sep 25. pii: S0167-8140(14)00388-0.