Stereotactic body radiotherapy using a radiobiology-based regimen for stage I nonsmall cell lung cancer: a multicenter study.
BACKGROUND
The most common regimen of stereotactic body radiotherapy (SBRT) for stage I nonsmall cell lung cancer in Japan is 48 grays (Gy) in 4 fractions over 4 days. Radiobiologically, however, higher doses are necessary to control larger tumors, and interfraction intervals should be >24 hours to take advantage of reoxygenation. In this study, the authors tested the following regimen: For tumors that measured <1.5 cm, 1.5 to 3.0 cm, and >3.0 cm in greatest dimension, radiation doses of 44 Gy, 48 Gy, and 52 Gy, respectively, were given in 4 fractions with interfraction intervals of ≥3 days.


METHODS
Among 180 patients with histologically proven disease who entered the study, 120 were medically inoperable, and 60 were operable. The median patient age was 77 years (range, 29-92 years). SBRT was performed with 6-megavolt photons using 4 noncoplanar beams and 3 coplanar beams. Isocenter doses of 44 Gy, 48 Gy, and 52 Gy were received by 4 patients, 124 patients, and 52 patients, respectively.


RESULTS
The overall survival rate for all 180 patients was 69% at 3 years and 52% at 5 years. The 3-year survival rate was 74% for operable patients and 59% for medically inoperable patients (P = .080). The 3-year local control rate was 86% for tumors ≤3 cm (44/48 Gy) and 73% for tumors >3 cm (52 Gy; P = .050). Grade ≥2 radiation pneumonitis developed in 13% of patients (10% of the 44-Gy/48-Gy group and 21% of the 52-Gy group; P = .056). All other grade 2 toxicities developed in <4% of patients.


CONCLUSIONS
The SBRT protocol used in this study yielded reasonable local control and overall survival rates and acceptable toxicity. Dose escalation is being investigated.
Department of Radiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan. yshiba@med.nagoya-cu.ac.jp
Yuta
Y
Shibamoto
Chisa
C
Hashizume
Fumiya
F
Baba
Shiho
S
Ayakawa
Yoshihiko
Y
Manabe
Aiko
A
Nagai
Akifumi
A
Miyakawa
Taro
T
Murai
Hiromitsu
H
Iwata
Yoshimasa
Y
Mori
Mikio
M
Mimura
Satoshi
S
Ishikura
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000401:mortality / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000401:mortality / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D011853:Radiobiology; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage