Radiographic changes in lung of patients treated with stereotactic ablative body radiation therapy: low-dose volumes as the driving force for radiographic change

Abstract

Objective

To describe radiographic evidence of radiation pneumonitis (rRP) and fibrosis (rRF) and determine what dosimetric parameters correlate with rRP and rRF after stereotactic ablative radiation therapy (SABR) to the lung.

Methods

Ninety-eight follow-up computed tomography (CT) scans from 32 patients treated by SABR were retrospectively reviewed for CT appearance of rRP and rRF determined by the Ikezoe (≤6 months) and Koenig (≥7 months) systems. The dosimetric correlations for rRP, rRF, and fibrotic volume were analyzed.

Results

There was a 55 % incidence of rRP and 59 % incidence of rRF with a median follow-up of 10 months. Only the low-dose parameters V _2.5, V ₅, V ₇, and V ₁₀ (the volume of lung receiving more than 2.5, 5, 7, and 10 Gy of radiation, respectively) were correlated to the development of rRP (p < 0.05). No parameter correlated with rRF, but V ₅, V ₇, and V ₁₀ trended toward significance. The absolute fibrotic volume was correlated with the planning target volume (p = 0.01) and V ₇ (p = 0.02).

Conclusion

The development of rRP and the fibrotic volume after SABR was correlated with the volume of lung that received lower doses of radiation.

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