Treatment efficiency of volumetric modulated arc therapy in comparison with intensity-modulated radiotherapy in the treatment of prostate cancer

Purpose: Treatment with intensity-modulated radiation therapy (IMRT) is increasingly standard for prostate cancer. Volume-modulated arc therapy (VMAT) to deliver IMRT potentially enables shorter treatment time. The aim of this study was to test this hypothesis by measuring the average patient in-room time with VMAT versus dynamic multileaf collimator (DMLC) IMRT.

Methods: Custom institutional software (RTMetrix) was used to mine the treatment times from the record-and-verify database. The in-room time (the time between patient entry and exit) was computed for each patient using RTMetrix. Average room time was compared between VMAT patients (n = 44) and IMRT patients (n = 99). Subgroup comparisons (1-arc or 2-arc VMAT, 5-field or 7-field IMRT, and electromagnetic transponder [Calypso] or gold-marker tracking) were performed. For all comparisons, 2-tailed, 2-sample, equal variance Student's t-tests were used.

Results: Average room time was significantly shorter for all VMAT versus DMLC IMRT (P = .0014) procedures, along with VMAT versus 7-field DMLC IMRT (P < .001), but not VMAT versus 5-field DMLC IMRT (P = .81). Room time was longer for Calypso versus gold seed patients (P < .001), but VMAT reduced treatment time in Calypso patients (P = .01). This resulted in Calypso VMAT patients' having similar treatment times to non-Calypso DMLC IMRT patients (P = .220).

Conclusions: These data show that VMAT can shorten room times and improve patient throughput over 7-field DMLC IMRT. Additionally, the data demonstrate that treatment with VMAT permits the use of advanced prostate tracking (Calypso), resulting in similar room times as with standard 7-field DMLC IMRT with conventional tracking.