Lung metastasis treatment with Stereotactic Body Radiation Therapy: a single institution experience
PO-1609
Abstract
Lung metastasis treatment with Stereotactic Body Radiation Therapy: a single institution experience
Authors: Susana Costa1, Fausto Sousa2, Pedro Leite-Silva3, Dora Gomes1, Olga Sousa1
1Instituto Português de Oncologia do Porto, Radiotherapy, Porto, Portugal; 2Centro Hospitalar Universitário São João, Radiotherapy, Porto, Portugal; 3Instituto Português de Oncologia do Porto, Cancer Epidemiology Group-Research Center, Porto, Portugal
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Purpose or Objective
Stereotactic body radiation therapy (SBRT) has an emerging role in the treatment of inoperable lung metastasis. This study aims to evaluate the efficacy of SBRT and identify prognostic factors influencing survival and local control.
Material and Methods
Unicentric retrospective study, of 162 patients (250 lesions), with lung metastasis, treated with SBRT, between 2013 and 2020. Patients lost to follow-up were excluded. Primary and metastatic tumor characteristics, treatment and follow-up data were evaluated.
Results
The median age was 67 years and 64% were male. The primary tumor was mainly colorectal (65%), followed by breast (6.2%) and other origins (28%). Eighty seven per cent of patients presented metachronous metastasis. Sixty-four per cent were treated for a single metastasis, 32% for 2-3 and 4.3% for ≥3. The prescribed total dose was 30-34Gy in single fraction (49%) and 40-50Gy in 4 to 5 fractions. Sixty-five per cent of lesions were treated with a BED10 >100. Median total volume of metastasis was 2.2cc [0.088-104] and median diameter was 14mm [1.00-61.0].
The median follow-up was 32.5 months. Two and 5-years overall survival (OS) rates were 84.2% and 46.6%. For progression-free survival (PFS), 2- and 5-years rates were 36.4% and 20.3% and for local control (LC) 80.9% and 75.1%, respectively. OS (p=0.97) and PFS (p=0.16) were not statistical different between colorectal cancer and other primary tumors. Colorectal cancer showed tendency for worst local control compared with other tumors (p=0.055).
The first location of disease progression was: 54% regionally, 9.3% locoregionally and 6.2% regionally and at distance; 15% at the distance; 11% progression in the field. No patient experienced grade toxicity ≥3.
At the univariate analysis, age (≥70 years) was a prognostic factor for regional-PFS (lung metastasis outside the SBRT treatment field; HR 0.42) and PFS (HR 0.55). The administration of systemic treatment previous to SBRT (≥3 lines) also presented statistical significance for regional-PFS (HR 2.46) and PFS (HR 2.23). The dimensions of metastasis, namely diameter (≥25mm) and volume (≥10cc) were predictive factors for worst OS (HR 2.77 and HR 3.50, respectively) and distance-PFS (HR 2.09 and HR 2.59, respectively). The presence of extrapulmonary disease (EPD) was a significative predictive factor for worst PFS (HR 1.81), including regional-PFS (HR 1.71) and distance-PFS (HR 3.01). For local control, the lesion diameter and volume were the only variables marginally significant (HR 1.03, for both).
In multivariate analysis, volume and EPD continued significant predictive factors for regional-PFS and distance-PFS. Age was also statistically significant for regional-PFS. PFS was significantly influenced by age and EPD.
Conclusion
SBRT is an effective and safe option for local treatment of lung metastasis, with a local control rate similar to described in the literature.
Age, volume of pulmonary metastasis and presence of extrapulmonary disease were important prognostic factors.