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Recent advances in automated treatment planning demonstrated improved plan quality and best practice reducing routine planning workload. In this study, a not yet commercially available fully-automated lexicographic optimisation (LO) planning, called mCycle (Elekta AB, Stockholm), has been validated for locally advanced cervical cancer.

Twenty cervical cancer treatment plans (50 Gy in 25 fx) delivered between November 2019 and July 2021 have been retrospectively selected and re-planned by mCycle (Monaco 5.59.13). Constraints and objectives were sequentially optimized by multi-criterial optimization (MCO) according to an a-priori assigned priority list, a so-called Wish List (WL). Four patient sets have been used to achieve a robust WL. Main criteria for planning approval were a target coverage V_95% > 97% (acceptable > 95%), target D_1% < 105%, a bowel volume receiving more than 45 Gy less than 195 cm³ (V_{45 Gy} < 195 cm³), rectum and bladder spared as much as possible. Manual plan (MP) and mCycle plans (mCP) were compared in terms of dose-volume constraints and plan complexity, i.e. MUs and modulation degree (MD), performing the Wilcoxon Mann Whitney test to assess statistical significance (α=0.05). Plan deliverability was verified by treatment QA.

The re-planning of 20 plans took 3 working days. Plan comparison showed an increased target dose coverage passing from a V_95% of (97.1 ± 1.2)% for MP to (98.1 ± 2.5)% for mCP (p = 0.002). The median bowel V_45Gy, rectum and bladder mean doses were 183.2 cm³, 39.4 Gy, and 40.7 Gy for MP and 189.7 cm³, 38.0 Gy, and 38.8 Gy for mCP, respectively (p > 0.05). The average modulation degree was 3.1 ± 0.4 and 3.3 ± 0.3 for MP and for mCP, respectively (p > 0.05). The average MUs were increased, registering 733.5 ± 84.0 and 797.3 ± 65.6 for MP and mCP, respectively (p = 0.02) but registering a comparable gamma analysis (local 3%/3mm).

The novel mCycle autoplanning produced high-quality clinically acceptable plans significantly reducing the overall planning time: at our Institution, medical physicists are typically given one day to optimize one cervical cancer treatment. While the OAR sparing was comparable between MP and mCP, the target coverage was significantly increased. Despite the higher MU number, the plan deliverability has been preserved. The validation showed the mCycle capability to generate high-quality deliverable plans according to institutional-specific planning protocols.