Treatment of large stage I-II lung tumors using stereotactic body radiotherapy (SBRT): planning considerations and early toxicity.
OBJECTIVE
To study the dosimetric predictors of early clinical toxicity following SBRT in patients with lung tumors and planning target volumes (PTV) exceeding 80 cm(3).


METHODS
Eighteen consecutive patients who were treated using volumetric modulated arc therapy (RapidArc™) were assessed. All were either unfit or refused to undergo surgery or chemoradiotherapy. PTV planning objectives were as used in the ROSEL study protocol. Clinical toxicity was scored using Common Toxicity Criteria AE4.0. Lung volumes receiving 5, 10, 15, and 20 Gy (V(5), V(10), V(15) and V(20)) and mean lung dose were assessed and correlated to symptomatic radiation pneumonitis (RP).


RESULTS
Median age, age-adjusted Charlson-comorbidity score and PTV size were 74, 7.5 and 137 cm(3), respectively. At a median follow-up of 12.8 months, 8 deaths were recorded: 5 arising from comorbidity, 2 were potentially treatment-related and 1 had local recurrence. RP was reported in 5 patients (grade 2 in 3 and grade 3 in 2). All RP occurred in plans without a high priority optimization objective on contralateral lung. Acute RP was best predicted by contralateral lung V(5) (p<0.0001).


CONCLUSIONS
After SBRT using RapidArc in lung tumors >80 cm(3), the contralateral lung V(5) best predicts RP. Limiting contralateral lung V(5) to <26% may reduce acute toxicity.
Ong
Chin Loon
CL
Department of Radiation Oncology, VU University Medical Center, Amsterdam, The Netherlands. c.ong@vumc.nl
Palma
David
D
Verbakel
Wilko F A R
WF
Slotman
Ben J
BJ
Senan
Suresh
S
D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology / Q000601:surgery*; D005260:Female; D006801:Humans; D008168:Lung / Q000528:radiation effects; D008175:Lung Neoplasms / Q000473:pathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011832:Radiation Injuries / Q000209:etiology / Q000473:pathology*; D017564:Radiation Pneumonitis / Q000209:etiology / Q000473:pathology; D016634:Radiosurgery / Q000009:adverse effects; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted