ESTRO 2021 Abstract Book

S993

ESTRO 2021

Peripheral

118 (90.1%)

CCT

Yes

28 (21.4%)

No

103 (78.6%)

PM

0.44 (0.39-0.52)

PI

107.3 (58.5-162.4)

Local Recurrence Yes

13 (9.9%)

No 118 (90.1%) 1. Data are median (25th-75th interquartile range) unless otherwise indicated.

2. Abbreviations: SCC=Squamous cell carcinoma; AD=Adenocarcinoma; NSCLC=Non-small cell lung cancer, not otherwise specified; BED10=Biologically effective dose when α/β = 10; CCT=Whether concurrent chemotherapy or targeted therapy was used; PM=Plan averaged beam modulation; PI=Plan averaged beam irregularity.

Figure 1 . Equations of plan complexity. Where MU ij is the area of all MLC openings at each control point; U(AA ij

is the monitor units (MU) of control point j in beam i; AA ij ) is the union area of all apertures of beam i; AP is

the perimeter of MLC aperture.

Results The median follow-up time was 22.4 months (interquartile range: 11.8-34.6). Cohort PM and PI varied largely ranging from 0.27 to 0.80 and 14.41 to 470.13 respectively. Prognostic capacity of PM was suggested using RSF based on the Variable importance and Minimal depth methods. The survival curves in Figure 2 show that shorter LRFS was significantly associated with higher PM (p=0.042), but was not significant for higher PI (p=0.11).