Dose prescription and reporting in stereotactic body radiotherapy: A multi-institutional study

Background and purpose: Radiation dose prescriptions are foundational for optimizing treatment efficacy and limiting treatment-related toxicity. We sought to assess the lack of standardization of SBRT dose prescriptions across institutions.

Materials & methods: Dosimetric data from 1298 patients from 9 academic institutions treated with IMRT and VMAT were collected. Dose parameters D₁₀₀, D₉₈, D₉₅, D₅₀, and D₂ were used to assess dosimetric variability.

Results: Disease sites included lung (48.3 %) followed by liver (29.7 %), prostate (7.5 %), spine (6.8 %), brain (4.1 %), and pancreas (2.5 %). The PTV volume in lung varied widely with bimodality into two main groups (22.0-28.7 cm³) and (48.0-67.1 cm³). A hot spot ranging from 120-150 % was noted in nearly half of the patients, with significant variation across institutions. A D₅₀ ≥ 110 % was found in nearly half of the institutions. There was significant dosimetric variation across institutions.

Conclusions: The SBRT prescriptions in the literature or in treatment guidelines currently lack nuance and hence there is significant variation in dose prescriptions across academic institutions. These findings add greater importance to the identification of dose parameters associated with improved clinical outcome comparisons as we move towards more hypofractionated treatments. There is a need for standardized reporting to help institutions in adapting treatment protocols based on the outcome of clinical trials. Dosimetric parameters are subsequently needed for uniformity and thereby standardizing planning guidelines to maximize efficacy, mitigate toxicity, and reduce treatment disparities are urgently needed.