ESTRO 2024 - Abstract Book

S1737

Clinical - Lung

ESTRO 2024

Clinical and Molecular Medicine, Trondheim, Norway. 10 University of Copenhagen, Department of Clinical Medicine, Copenhagen, Denmark

Purpose/Objective:

NARLAL 2 is a randomized controlled multicenter phase III trial evaluating the effect of inhomogeneous dose escalation in patients with locally advanced non-small cell lung cancer treated with concomitant chemoradiotherapy (NCT02354274). The primary endpoint is the loco-regional control rate at one year. After trial conclusion in March 2023, we hereby present the dosimetric compliance analysis.

Material/Methods:

A total of 350 patients were 1:1-randomized to either standard homogeneously dosed 66 Gy in 33 fractions (fx) or inhomogeneous isotoxic dose escalation. Dose escalation was driven by the 18-FDG high uptake volumes (PET-GTV) on a pre-treatment 18-FDG PET/CT scan. Maximum mean doses were 95 Gy/33 fx for the primary tumor and 74 Gy/33 fx for the lymph nodes in the dose escalated plans, see Figure 1. Only large lymph node volumes > 4 ccm were dose escalated. Before randomization, two treatment plans were made and approved for each patient: a standard and an escalated plan. Between the two plans, lung iso-toxicity was ensured by keeping the difference in mean lung dose (MLD) < 1 Gy and lung V20 <2%. Dose escalation was limited by strictly prioritized constraints to organs at risk (OARs), see Table 1. Target volumes, mean target and escalation volume (PET-GTV) doses, compliance to OAR constraints, and differences in MLD and mean heart dose (MHD) between each patient’s standard and escalated plans are reported as median and interquartile range values.

Tabel 1: Constraint for and doses to organs at risk.

Standard median[IQR]

Escalated median[IQR]

OAR

Constraint [unit]

Lung

13.74 [11.59;16.63]

13.93 [11.63;16.74]

Mean dose < 20 [Gy]

22.89 [18.17;27.75]

22.93 [17.82;27.22]

V 20Gy < 35 [%]

50.99 [40.14;59.11]

50.08 [40.14;58.95]

V 5Gy * [%]

Heart

8.18 [3.30;13.94]

8.09 [3.31;13.90]

Mean dose* [Gy]

2.45 [0.19;5.43]

2.47 [0.18;5.77]

V 50Gy < 25 [%]

4.2 [0.45;8.88]

4.30 [0.55;9.50]

V 40Gy < 30 [%]

10.07 [1.62;19.05]

9.42 [1.66;18.79]

V 25Gy < 50 [%]