(Sunday, 7/12/2020) [Eastern Time (GMT-4)]
Room: AAPM ePoster Library
Purpose: Stereotactic body radiation therapy (SBRT) is increasingly used as a curative strategy for oligometastatic tumors. In this work, the dose response of oligometastases treated with various SBRT fractionation schedules were evaluated, compared to a well-established early stage Lung dose response relationship for various fractionation schedules including SBRT.
Methods: Literature review was performed in PubMed with keywords oligometatstasis and SBRT. Clinical outcome data with more than 50 patients that report local control rate and fractionation schedules were included. Detailed treatment information was collected from each cohort for model simulation. Previously developed tumor response model (Jeong et al., CCR 2017) was applied to normalize the treatment efficacy of different fractionation schedules, in terms of the model equivalent dose in 2Gy/fx (EQD2_model). The dose response of each cohort was compared with the early stage lung dose response curve.
Results: Total 21 patient cohorts were identified with 1643 patients and 2235 lesions. Compared to the early stage lung dose response curve (TD50=62.1Gy in EQD2_model, ?5050=1.5), the dose response of the oligometastases broadly dispersed, depending mainly on the primary origin of the metastatic tumor. While the cohorts with mixed primary origins generally agree with the previously found dose response from lung SBRT, cohorts with colorectal cancer origin seem to be more resistant that requires about 60% extra dose in EQD2_model. Oligometastases with prostate or ovarian origin were evaluated to be more sensitive with lower TD50 values (30.9 and 38.5Gy, respectively).
Conclusion: In this work, dose response of oligometastatic tumors to SBRT was evaluated. Primary origin seems to affect the dose response relationship. Oligometastases originated from colorectal cancer are more resistant, while prostate or ovarian origin are more sensitive. Further investigation with more data is needed to validate these findings.
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