Vertebral Fractures After Stereotactic Ablative Radiotherapy of Lung Tumors

Todd A. Aguilera MD PhD1, Nicholas Trakul MD PhD2, David B. Shultz MD PhD1, Peter G Maxim PhD1, Maximilian Diehn MD PhD1, and Billy W Loo Jr. MD PhD1

1Department of Radiation Oncology, Stanford Cancer Institute, Stanford CA 2Department of Radiation Oncology, USC, Los Angeles CA; Correspondence toddagu1@stanford.edu

Poster #57010

Background• Not much is known about risk of vertebral fracture after stereotactic radiation of

lung tumors

Objective• Evaluate Stanford SABR experience for vertebral fractures that developed in the

coplanar treatment field

Results• Six of 236 patients (2.5%) developed fractures to vertebral bodies that received

considerable dose• Patients were predominantly women and had low bone density

Table of 6 patients and pertinent clinical factors

Sex (Age)

Stg Tx Dose/ fraction #

Max dose (Gy)

Distance to VB (cm)

Prior or multi fx

Rib Fx

Osteo-penia

Time to fx (mo)

1 W(87) 1A CK 30/1 5.5 7.2 prior Y 13

2 W(66) 1A CK 25/1 2.5 10.5 multi Y 24

3 W(64) 1A CK 50/4 48 <1 28

4 M(77) 3B VMAT 25/1 x 2, 20/1

5.5/ 26 <1, 4 multi 12/21

5 W(89) 1B VMAT 50/4 35 <1 Y 9

6 W(81) 1B VMAT 54/3 12.2 6 Y 14

CK= Cyberknife; VMAT= Linac based volume modulated arch therapy; VB= vertebral body

13 mth 25 mth

5 Gy3 Gy 25 Gy10 Gy

5 Gy

Pretreatment 12 months 21 months

This patient had 3 lesions treated and developed fractures at 2 levels.

T8 T10

Vertebral fracture after lung SABR: Summary

• Stereotactic radiation may increase vertebral fracture risk in high risk patients. – Doses as low as 5 Gy may increase risk– One patient had prior fracture– Two patients developed fractures concurrently at untreated levels

• Postmenopausal women with low bone density appear to have the greatest risk.

• At least 2 of 4 patients with clinical follow up had associated pain