Correlation of dose computed using different algorithms with local control following stereotactic ablative radiotherapy (SABR)-based treatment of non-small-cell lung cancer.
OBJECTIVE
To retrospectively compute dose distributions for lung cancer patients treated with SABR, and to correlate dose distributions with outcome using a tumor control probability (TCP) model.


METHODS
Treatment plans for 133 NSCLC patients treated using 12 Gy/fxn × 4 (BED=106 Gy), and planned using a pencil-beam (1D-equivalent-path-length, EPL-1D) algorithm were retrospectively re-calculated using model-based algorithms (including convolution/superposition, Monte Carlo). 4D imaging was performed to manage motion. TCP was computed using the Marsden model and associations between dose and outcome were inferred.


RESULTS
Mean D95 reductions of 20% (max.=33%) were noted with model-based algorithms (relative to EPL-1D) for the smallest tumors (PTV<20 cm(3)), corresponding to actual delivered D95 BEDs of ≈ 60-85 Gy. For larger tumors (PTV>100 cm(3)), D95 reductions were ≈ 10% (BED>100 Gy). Mean lung doses (MLDs) were 15% lower for model-based algorithms for PTVs<20 cm(3). No correlation between tumor size and 2-year local control rate was observed clinically, consistent with TCP calculations, both of which were ≈ 90% across all PTV bins.


CONCLUSIONS
Results suggest that similar control rates might be achieved for smaller tumors using lower BEDs relative to larger tumors. However, more studies with larger patient cohorts are necessary to confirm this possible finding.
Department of Radiation Oncology, Henry Ford Hospital, Detroit, USA. Electronic address: ichetty1@hfhs.org.
Indrin J
IJ
Chetty
Suneetha
S
Devpura
Dezhi
D
Liu
Daiquan
D
Chen
Haisen
H
Li
Ning Winston
NW
Wen
Sanath
S
Kumar
Correen
C
Fraser
M Salim
MS
Siddiqui
Munther
M
Ajlouni
Benjamin
B
Movsas
D000465:Algorithms; D002289:Carcinoma, Non-Small-Cell Lung / Q000532:radiotherapy / Q000601:surgery*; D056973:Four-Dimensional Computed Tomography / Q000379:methods; D006801:Humans; D008175:Lung Neoplasms / Q000532:radiotherapy / Q000601:surgery*; D009010:Monte Carlo Method; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012189:Retrospective Studies
Dose algorithms; Non-small-cell lung cancer; Outcomes; SABR; Tumor control probability (TCP)