Personalized Radiation Therapy of Breast Cancers May Not Incur Substantial Increase in Treatment Delivery Time

Abstract

A retrospective investigation was performed examining the treatment delivery time for breast cancer patients treated in our clinics. We hypothesized that the use of highly personalized radiation treatments of breast cancers might increase treatment delivery time substantially. We identified patients with breast cancers who completed non-IMRT tangential beam radiation therapy (RT) in the last three years. All patients received a whole breast radiation dose of 45-50 Gy at 1.8-2.0 Gy/fraction or 42.5 Gy at 2.66 Gy/fraction. Boost treatments to the tumor bed were excluded in this study. Personalizing treatment plans based on each individual’s normal tissue and tumor anatomy for optimal target coverage and critical organ sparing required using various numbers of radiation fields, beam energies, intensity modulation techniques and active breathing control (ABC). Resulting costs in delivering the plans were evaluated in terms of the time spent to complete each treatment fraction through the course. We measured the time spent on individual fractions by determining the total time from the moment the first treatment field was beamed on to the completion of last treatment field (averaged over all fractions). Treatment delivery records of 253 patients were analyzed, of whom 69% (N = 175) received radiation to whole breast (WB) only, 18% (N = 45) to WB plus axillary nodes (WB+Ax), 4% (N = 10) to WB plus internal mammary nodes (WB+IM), and 9% (N = 23) to WB plus axillary and IM nodes (WB+Ax+IM). Timing records for a total of 6,808 delivered fractions were analyzed to obtain the average treatment times. 27% (N = 69) of the studied patients were treated with ABC, of whom, those receiving RT to WB only had treatment times of 4.2±0.2, 4.7±0.3, 5.3±0.4, and 5.6±0.4 min respectively corresponding to 5 through 8 radiation fields treated, while those receiving RT to WB+Ax had a treatment time of 9.9±2.5 min. In the non-ABC group, patients receiving RT to WB only had treatment times of 2.9±0.3, 3.3±0.7, 3.7±0.4, 4.1±0.6, 4.5±0.9, 4.4±0.3, and 5.2±0.9 min respectively for 2 to 8 treatment fields used. Those receiving RT to WB+Ax, WB+IM or WB+Ax+IM had treatment times of 7.5±2.2, 7.4±2.8, and 13.2±3.1 min respectively. Among patients who were treated to WB only, the treatment times were 4.0±0.9 and 4.9±0.6 min for the non-ABC and ABC groups, respectively. For patients treated to WB+Ax, WB+IM or WB+Ax+IM, the average treatment times were respectively 8.3±2.3, 7.4±2.8, and 13.2±3.1 min. The average time required to deliver individual treatment fraction increases with the number of radiation fields used. The maximum increment is less than two and half minutes per fraction, which will not significantly impact overall clinical throughput. A time increment of similar magnitude is also observed in patients treated with ABC compared to those without ABC.