New approach in lung cancer radiotherapy offers better normal tissue sparing

Regional lung avoidance by CT numbers to reduce radiation-induced lung damage risk in non-small-cell lung cancer: a simulation study

Background: Selective avoidance aims at sparing functional lung regions. Here, we preferentially direct radiation to irreversibly nonfunctional lung areas based on planning CT imaging to reduce functional lung damage.Materials and methods: For 12 stage I-IV NSCLC patients, 5 lung substructures were segmented on the planning CT, combining voxels <-900HU, -900HU to -801HU, -800HU to -701HU, -700HU to -601HU and ≥-600HU (Level 1 to 5). Two VMAT plans were optimized: a reference plan blinded from substructures and a selective avoidance plan (AV) imposing gradually stricter constraints on Level 1-5, based on previously validated associations between lung subvolume baseline density and density increase (ΔHU) after treatment. Characteristics of treatment plans were evaluated, including subvolumes, dose, and predicted ΔHU (with reported 95% CI reflecting prediction model uncertainty).Results: Segmented substructures were on average 477 cc, 1157 cc, 484 cc, 69 cc, and 123 cc (Level 1-5). AV plans could spare Level 3-5, e.g., mean dose decrease of 3.5 Gy (range 0.6 Gy; 6.0 Gy) for Level 5, p<.001. This significantly reduced the average lung mass with predicted ΔHU>20HU by 12.5 g (95% CI: 5.4-16.9) and 27.1 g (95% CI: 10.2-32.9) for a median and upper 10th percentile patient susceptibility for damage simulation, respectively.Conclusions: Lung damage avoidance based on CT density is feasible and easy to implement. A biomarker providing a reliable selection of patients with high susceptibility for lung damage will be crucial to show the clinical relevance of this avoidance planning strategy.

Lung toxicity after radiation in childhood: Results of the International Project on Prospective Analysis of Radiotoxicity in Childhood and Adolescence

BACKGROUND AND PURPOSE

This study presents the evaluation of acute and late toxicities of the lung in children and adolescents after irradiation in terms of dose-volume effects.

MATERIALS AND METHODS

Irradiated children and adolescents in Germany have prospectively been documented since 2001 in the "Registry for the Evaluation of Side-Effects after Radiotherapy in Childhood and Adolescence (RiSK)"; in Sweden since 2008 in the RADTOX registry.

RESULTS

Up to April 2012, 1,392 children were recruited from RiSK, and up to June 2013, 485 from the RADTOX-registry. Of these patients, 295 were irradiated to the lung. Information about acute toxicity was available for 228 patients. 179 patients have been documented concerning late toxicity (≥grade 1: n = 28). The acute toxicity rate was noticeably higher in children irradiated with 5-20Gy (p < 0.05). In the univariate analysis, a shorter time until late toxicity was noticeably associated with irradiation with 5-15Gy (p < 0.05).

CONCLUSION

Acute and late toxicities appear to be correlated with higher irradiation volumes and low doses. Our data indicate that similar to the situation in adult patients, V5, V10, V15 and V20 should be kept as low as possible (e.g., at least V5 < 50%, V10 and V15 < 35% and V20 < 30%) in children and adolescents to lower the risk of toxicity.