Dose-volume comparison of proton radiotherapy and stereotactic body radiotherapy for non-small-cell lung cancer.
OBJECTIVE
This study designed photon and proton treatment plans for patients treated with hypofractionated proton radiotherapy (PT) at the Southern Tohoku Proton Therapy Center (STPTC). We then calculated dosimetric parameters and compared results with simulated treatment plans for stereotactic body radiotherapy (SBRT), using dose--volume histograms to clearly explain differences in dose distributions between PT and SBRT.


METHODS
Twenty-one patients with stage I non-small-cell lung cancer (stage IA, n = 15 patients; stage IB, n = 6 patients) were studied. All tumors were located in the peripheral lung, and total dose was 66 Gray equivalents (GyE) (6.6 GyE/fraction). For treatment planning, beam incidence for proton beam technique was restricted to two to three directions for PT, and seven or eight noncoplanar beams were manually selected for SBRT to achieve optimal planning target volume (PTV) coverage and minimal dose to organs at risk.


RESULTS
Regarding lung tissues, mean dose, V5, V10, V13, V15, and V20 values were 4.6 Gy, 13.2%, 11.4%, 10.6%, 10.1%, and 9.1%, respectively, for PT, whereas those values were 7.8 Gy, 32.0%, 21.8%, 17.4%, 15.3%, and 11.4%, respectively, for SBRT with a prescribed dose of 66 Gy. Pearson product moment correlation coefficients between PTV and dose--volume parameters of V5, V10, V15, and V20 were 0.45, 0.52, 0.58, and 0.63, respectively, for PT, compared to 0.52, 0.45, 0.71, and 0.74, respectively, for SBRT.


CONCLUSIONS
Correlations between dose--volume parameters of the lung and PTV were observed and may indicate that PT is more advantageous than SBRT when treating a tumor with a relatively large PTV or several tumors.
Kadoya
Noriyuki
N
Department of Medical Physics, Southern Tohoku Proton Therapy Center, Southern Tohoku Institute of Neuroscience, Koriyama, Fukushima, Japan. noriyuki_kadoya@yahoo.co.jp
Obata
Yasunori
Y
Kato
Takahiro
T
Kagiya
Masaru
M
Nakamura
Tatsuya
T
Tomoda
Takuya
T
Takada
Akinori
A
Takayama
Kanako
K
Fuwa
Nobukazu
N
D000230:Adenocarcinoma / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery; D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery; D002294:Carcinoma, Squamous Cell / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery; D008297:Male; D058958:Organs at Risk; D017785:Photons / Q000627:therapeutic use; D061766:Proton Therapy; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D011522:Protons
D011522:Protons