Lean Thinking to manage a national working group on physics aspects of Stereotactic Body Radiation Therapy.

Purpose: To report how the adoption of a Lean Thinking mindset in the management of a national working group (WG) on the physics of stereotactic body radiation therapy (SBRT) contributed to achieve SBRT standardization objectives.

Methods: Vision for the WG has been established as fragmentation reduction and process harmonization enhancement in SBRT for Italian centers. Two main research themes of the technical aspects of SBRT emerged as areas with major standardization improvement needs, small field dosimetry and SBRT planning comparisons, to be investigated through multi-institutional studies. The management of the WG leveraged on the Lean concept of fostering self-organization in a non-hierarchical environment. Four progressive involvement levels were defined for each study. No specific "scientific" pre-experience was required to propose and coordinate a project, just requiring a voluntary commitment. People engagement was measured in terms of number of published articles. The standardization goals have been conducted through a simplified "5S" (Sort, Set in Order, Shine, Standardize, and Sustain) methodology, first considering a phase of awareness (the first three "S"), then identifying and implementing standardization actions (the last two "S").

Results: Since the beginning, 157 medical physicists joined the AIFM/SBRT-WG. Twenty-four papers/reviews/letters have been published in the period 2014-2019 on major radiation oncology journals, authored by >100 physicists (>50% working in small hospitals). Six over 12 first authors worked in peripheral/small hospitals, with no prior publication as first author. These studies contributed to the awareness and standardization phases for both small-field dosimetry and planning. In particular, errors in small-field measurements in 8% of centers were detected thanks to a generalized output factor curve in function of the effective field size created by averaging data available from different Linacs. Furthermore, planner's experience in SBRT was correlated with dosimetric parameters in the awareness phase; while sharing median dose volume histograms (DVHs) reduced variability among centers while keeping the same level of plan complexity. Finally, all the dosimetric parameters statistically significant to the planner experience during the awareness phase, were no longer significantly different in the standardization phase.

Conclusions: The experience of our SBRT-WG has shown how a Lean Thinking mindset could foster the SBRT procedure standardization and spread the physics of SBRT knowledge, enhancing personal growth. Our expectation is to inspire other scientific societies that have to deal with fragmented contexts or pursue processes harmonization through Lean principles.