An Analysis of Learning Curve Effect on the Speed and Quality of High Dose Rate Prostate Brachytherapy Procedures

Abstract

To evaluate the impact of learning curve effect on the provision of High Dose Rate (HDR) prostate brachytherapy boost at a recently initiated program within a smaller Canadian Academic Cancer Center. From 2015 to 2019, 266 patients with intermediate or unfavorable risk prostate cancer were treated with single fraction HDR prostate brachytherapy boost (15 Gy), followed by combination external beam radiation therapy (37.5 – 46 Gy) at a single Canadian cancer institution. Detailed time records were recorded for all phases of the procedures including: total procedure time, catheter insertion / placement, contouring, second oncologist check, catheter reconstruction, planning / dose optimization, QA / second checks, and treatment delivery. Dosimetric values from the delivered plans were also analyzed, including metrics for: Prostate (D90, V100, V150, V200), urethra (D10, max), and rectum (V75, V80, V100, max). The experience of each team member (previous number of procedures performed since program inception) was also recorded. Radiation Oncologist (RO) experience was not a significant predictor of total procedure time (p = 0.163) nor total catheter placement time (p = 0.583). Planner experience was significantly correlated with reduced catheter reconstruction time, and consequently, total procedure time (β = -0.376 minutes / case experience, P<0.001). There were statistically significant differences in mean prostate D90 (105.36 vs 106.05%, p = 0.04), V100 (94.69% vs. 95.31%, p = 0.014), and urethra D10 (113.61 vs. 112.74%, p = 0.008) when comparing dosimetry from an oncologist’s first 20 cases compared to those afterwards. RO experience was correlated with improvement in prostate D90 (β = 0.000156, p = 0.008), V100 (β = 0.000144, p = 0.001), and V200 (β = -0.000152, p = 0.008), and urethra D10 (β = -0.000159, p = 0.011). HDR Prostate brachytherapy can provide radiotherapy with excellent dosimetric characteristics regardless of previous institutional experience. In our study, institutional oncologist experience provided a modest, but measurable improvement in dosimetric quality. Institutional experience reduced total procedure time; this improvement was mainly attributable to the planner. These findings support the use of HDR prostate brachytherapy as a robust technique even for newer adopters, and may further inform cancer centers initiating new HDR Brachytherapy programs or training new staff.