Retrospective cohort study of bronchial doses and radiation-induced atelectasis after stereotactic body radiation therapy of lung tumors located close to the bronchial tree.

PURPOSE

To evaluate the dose-response relationship between radiation-induced atelectasis after stereotactic body radiation therapy (SBRT) and bronchial dose.

METHODS AND MATERIALS

Seventy-four patients treated with SBRT for tumors close to main, lobar, or segmental bronchi were selected. The association between incidence of atelectasis and bronchial dose parameters (maximum point-dose and minimum dose to the high-dose bronchial volume [ranging from 0.1 cm(3) up to 2.0 cm(3)]) was statistically evaluated with survival analysis models.

RESULTS

Prescribed doses varied between 4 and 20 Gy per fraction in 2-5 fractions. Eighteen patients (24.3%) developed atelectasis considered to be radiation-induced. Statistical analysis showed a significant correlation between the incidence of radiation-induced atelectasis and minimum dose to the high-dose bronchial volumes, of which 0.1 cm(3) (D(0.1cm3)) was used for further analysis. The median value of D(0.1cm3) (α/β = 3 Gy) was EQD(2,LQ) = 147 Gy3 (range, 20-293 Gy3). For patients who developed atelectasis the median value was EQD(2,LQ) = 210 Gy3, and for patients who did not develop atelectasis, EQD(2,LQ) = 105 Gy3. Median time from treatment to development of atelectasis was 8.0 months (range, 1.1-30.1 months).

CONCLUSION

In this retrospective study a significant dose-response relationship between the incidence of atelectasis and the dose to the high-dose volume of the bronchi is shown.