PURPOSE: To report on the primary and secondary outcomes of a prospective
clinical trial of electromagnetic-guided multileaf collimator (MLC) tracking
radiation therapy for prostate cancer.
METHODS AND MATERIALS: Twenty-eight men with prostate cancer were treated with
electromagnetic-guided MLC tracking with volumetric modulated arc therapy. A
total of 858 fractions were delivered, with the dose per fraction ranging from 2
to 13.75 Gy. The primary outcome was feasibility, with success determined if >95%
of fractions were successfully delivered. The secondary outcomes were (1) the
improvement in beam-target geometric alignment, (2) the improvement in dosimetric
coverage of the prostate and avoidance of critical structures, and (3) no acute
grade ≥3 genitourinary or gastrointestinal toxicity.
RESULTS: All 858 planned fractions were successfully delivered with MLC tracking,
demonstrating the primary outcome of feasibility (P < .001). MLC tracking
improved the beam-target geometric alignment from 1.4 to 0.90 mm
(root-mean-square error). MLC tracking improved the dosimetric coverage of the
prostate and reduced the daily variation in dose to critical structures. No acute
grade ≥3 genitourinary or gastrointestinal toxicity was observed.
CONCLUSIONS: Electromagnetic-guided MLC tracking radiation therapy for prostate
cancer is feasible. The patients received improved geometric targeting and
delivered dose distributions that were closer to those planned than they would
have received without electromagnetic-guided MLC tracking. No significant acute
toxicity was observed.