Reirradiation dose constraints in clinical practice: Results of an international survey

Despite the increasing frequency of reirradiation (reRT) in cancer treatment, a critical lack of reliable dose constraint data remains. This study addresses this gap by collating current reRT constraints used in clinical practice across multiple centers, facilitating the development of more consistent and safer reRT guidelines.

A comprehensive survey collected data on reRT patient numbers, dose constraints, sources, and dose summation methods for 30 OARs. Information also included PRV margins, tissue recovery factors (TRF) with time intervals, α/β values, near-D_max definitions, and dose constraints in EQD2Gy for first and reRT courses. The relative difference (X_reRT) between cumulative reRT and first course constraints was calculated. Constraints with data from at least 7 centers were included for further analysis.

A median of 6 % of treatments in 17 participating centers were reRT. Most centers derived reRT constraints from the literature (81 %) or first course constraints (68 %). In total 209 cumulative near-D_max values for 19 OARs fulfilled n ≥ 7, yielding a median inter-center variation of 21 % (IQR). While α/β values were relatively consistent, substantial variations were seen in near-D_max volume definition, TRF, and PRV margins. The median X_reRT was 26 %, primarily attributed to the TRF which had a median value of 23 %.

This multi-centre survey identified a concerning median inter-centre variation of 21 % in cumulative reRT dose constraints, indicating substantial heterogeneity in current clinical practices. Further prospective studies with rigorous and standardized dose reporting are essential to refine reRT guidelines, enhancing patient safety and treatment efficacy.