Dosimetric Factors and Toxicity in Highly Conformal Thoracic Reirradiation

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• 作者：Michael S. Binkley ; BA^&lowast ; ; Susan M. Hiniker ; MD^&lowast ; ; Aadel Chaudhuri ; MD ; PhD^&lowast ; ; Peter G. Maxim ; PhD^&lowast ; ; ^&dagger ; ; Maximilian Diehn ; MD ; PhD^&lowast ; ; ^&dagger ; ; ^&Dagger ; ; Billy W. Loo Jr. ; MD ; PhD^&lowast ; ; ^&dagger ; ; ^{BWLoo@Stanford.edu" class="auth_mail" title="E-mail the corresponding author} ; David Benjamin Shultz ; MD ; PhD^§ ; ; ^‖ ; ^{David.Shultz@rmp.uhn.on.ca" class="auth_mail" title="E-mail the corresponding author}
• 刊名：International Journal of Radiation Oncology*Biology*Physics
• 出版年：2016
• 出版时间：15 March 2016
• 年：2016
• 卷：94
• 期：4
• 页码：808-815
• 全文大小：1232 K

文摘

We determined cumulative dose to critical structures, rates of toxicity, and outcomes following thoracic reirradiation.

Methods and Materials

We retrospectively reviewed our institutional database for patients treated between 2008 and 2014, who received thoracic reirradiation with overlap of 25% prescribed isodose lines. Patients received courses of hyperfractionated (n=5), hypofractionated (n=5), conventionally fractionated (n=21), or stereotactic ablative radiation therapy (n=51). Doses to critical structures were converted to biologically effective dose, expressed as 2 Gy per fraction equivalent dose (EQD2; α/β = 2 for spinal cord; α/β = 3 for other critical structures).

Results

We identified 82 courses (44 for retreatment) in 38 patients reirradiated at a median 16 months (range: 1-71 months) following initial RT. Median follow-up was 17 months (range: 3-57 months). Twelve- and 24-month overall survival rates were 79.6% and 57.3%, respectively. Eighteen patients received reirradiation for locoregionally recurrent non-small cell lung cancer with 12-month rates of local failure and regional recurrence and distant metastases rates of 13.5%, 8.1%, and 15.6%, respectively. Critical structures receiving ≥75 Gy EQD2 included spinal cord (1 cm³; n=1), esophagus (1 cm³; n=10), trachea (1 cm³; n=11), heart (1 cm³; n=9), aorta (1 cm³; n=16), superior vena cava (1 cm³; n=12), brachial plexus (0.2 cm³; n=2), vagus nerve (0.2 cm³; n=7), sympathetic trunk (0.2 cm³; n=4), chest wall (30 cm³; n=12), and proximal bronchial tree (1 cm³; n=17). Cumulative dose-volume (D cm³) toxicity following reirradiation data included esophagitis grade ≥2 (n=3, D1 cm³ range: 41.0-100.6 Gy), chest wall grade ≥2 (n=4; D30 cm³ range: 35.0-117.2 Gy), lung grade 2 (n=7; V20_{combined-lung} range: 4.7%-21.7%), vocal cord paralysis (n=2; vagus nerve D0.2 cm³ range: 207.5-302.2 Gy), brachial plexopathy (n=1; D0.2 cm³ = 242.5 Gy), and Horner's syndrome (n=1; sympathetic trunk D0.2 cm³ = 130.8 Gy). No grade ≥4 toxicity was observed.

Conclusions

Overlapping courses of reirradiation can be safely delivered with acceptable toxicity. Some toxicities occurred acutely at doses considered safe for a single course of therapy (esophagus). We observed rib fracture, brachial plexopathy, and Horner's syndrome for patients receiving high cumulative doses to corresponding critical structures.