Analysis of Biologically Equivalent Dose of Stereotactic Body Radiotherapy for Primary and Metastatic Lung Tumors

Abstract

PurposeThe purpose of this study was to determine the optimal biologically equivalent dose (BED) for stereotactic body radiotherapy (SBRT) by comparing local control rates in proportion to various total doses and fractionation schedules.Materials and MethodsThirty-four patients with early non-small-cell lung cancer and a single metastatic lung tumor were included in this study. Differences in local control rates were evaluated according to gender, primary tumor site, response, tumor size, and BED. For comparison of BEDs, the prescribed dose for SBRT was stratified according to three groups: high (BED > 146 Gy), medium to high (BED, 106 to 146 Gy), and low to medium (BED < 106 Gy).ResultsFor all patients, the overall local control rate was 85.3% at two years after treatment. Five local recurrences were observed, and, notably, all of them were observed in the low to medium BED group. Significantly higher local control rates were observed for patients with a complete response than for those with a partial response or stable disease (p < 0.001). Twenty-six patients with a tumor size of < 3 cm showed no dose-response relationship in the low to medium, medium to high, and high BED groups, whereas eight patients with a tumor size of ≥ 3 cm showed a significant dose-response relationship. The observed 2-year local recurrence-free survival rates in patients with a tumor size of < 3 cm and in those with a tumor size of ≥ 3 cm were 96.2% and 50.0%, respectively, which were significantly different (p=0.007).ConclusionBED > 100 Gy is required in order to achieve a > 85% local control rate regardless of tumor size. The optimal dose for small tumors of < 3 cm appears to be within a range below 150 Gy BED. Escalation of BED to high levels (> 150 Gy) may be required for patients with a tumor size larger than 3 cm.

Impact of Fractionation and Dose in a Multivariate Model for Radiation-Induced Chest Wall Pain

“…We therefore recommend considering a 4- or 5-fraction regimen in patients with targets near the CW or larger targets with a high associated dose to the CW. However, the prescription dose per fraction and V NTD have to be balanced with considerations of tumor control probability, and on the basis of current information the prescription biologically effective dose to the target should not be decreased <100 Gy, to maintain adequate tumor control probability (19–22). …”

Retrospective analysis of stereotactic ablative radiotherapy (SABR) for metastatic lung lesions (MLLs) in comparison with a contemporaneous cohort of primary lung lesions (PLLs)

“…This concept was confirmed by another study (6), and extrapolated for MLLs (8,16). However, this dogma is based on chi-square test (15) and log rank (6) univariate analysis and remains therefore controversial (17).…”

Stereotactic Ablative Body Radiotherapy for the Treatment of Spinal Oligometastases

“…The 2-year overall survival and freedom from local progression were 57% and 73%, respectively, with inferior local control possibly related to relatively gentle median dose / fractionation schedule of 30Gy in 5 fractions as compared to our 24Gy in 2 fractions, as previously described by Saghal et al [21] It is interesting that outcomes achieved in our study were similar to those achieved with SABR for other body sites where much higher doses are usually required. A threshold dose of BED10 > 100 Gy is often quoted as being required to achieve optimal local control in lung and liver metastases [22,23], which is much higher than the doses employed in this cohort. This is an important consideration in this patient cohort because it is speculated that the close proximity of spinal SABR target volumes to the spinal cord may restrict the dose that can be safely delivered, and may therefore have inferior outcomes compared to sites where higher doses are typically delivered.…”