(Sunday, 7/29/2018) 3:00 PM - 6:00 PM
Room: Exhibit Hall
Purpose: To retrospectively investigate tumor responses of lung Stereotactic Body Radiotherapy (SBRT) patients. To analyze the relation between optimal biologically equivalent dose (BED) and tumor responses for different SBRT prescriptions.
Methods: Treatment outcomes of multi-institutional lung SBRT patients were assessed with Computed Tomography (CT) follow-ups and max Standardized Uptake Value (SUV) from Positron Emission Tomography (PET). Compared the efficiency and accuracy between these diagnosis modalities, a tumor response criterion using post max SUV read from PET/CT taken around 3 months after treatment was introduced in this study. Biologically equivalent doses (BED) calculated using α/β of 10Gy were analyzed with assessments of tumor responses for different prescriptions.
Results: We found 3-month post max SUV could efficiently assess local tumor responses after lung SBRT. From our primary data for four SBRT prescriptions (9Gy×5, 10Gy×5, 11Gy×5, and 12Gy×4) historically recommended by RTOG, we observed that higher BED�₀ and lower tumor volume would achieve a higher complete response rate. The highest complete response rate was observed for smallest tumor volume (PTV�ᵥₑ = 6.8cc) with higher BED�₀ (105.6) of 12Gy×4 prescription. For 11Gy×5 prescription, the BED�₀ (115.5) was the highest, but its complete response rate (58%) was lower than 79% of 12Gy×4 prescription. We observed the PTV�ᵥₑ was 15.5cc for 11Gy×5 group, which was more than double of the average of tumor volume of 12Gy×4 group. Modification of the linear quadratic model and dose escalation for patients with larger tumor volume were discussed.
Conclusion: We suggest 3-month post max SUV read from PET/CT should become standard tumor response assessment for lung SBRT. Although SBRT with prescriptions resulting in a BEDâ‚?â‚€ > 100 experienced favorable tumor responses for normal non-small cell lung cancer (NSCLC), escalation of BEDâ‚?â‚€ to higher levels, e.g. 150Gy, may be beneficial for patients with larger tumors undergoing lung SBRT.
Keywords
Not Applicable / None Entered.
Taxonomy
TH- response assessment : General (most aspects)
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