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Meta-analysis of Toxicity and Treatment Outcomes With Stereotactic Ablative Radiotherapy for Oligometastatic Cancer


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In a systematic review and meta-analysis reported in JAMA Oncology, Lehrer et al found that stereotactic ablative radiotherapy (SABR) for oligometastatic cancer was associated with “clinically acceptable” rates of severe acute and late toxicities as well as 1-year disease outcomes.

As stated by the investigators: “The oligometastatic paradigm postulates that patients with a limited number of metastases can be treated with ablative local therapy to each site of disease with curative intent. SABR is a radiation technique that has become widely used in this setting. However, prospective data are limited and are mainly from single institutional studies.”

“In this meta-analysis, SABR appeared to be safe and effective in the setting of oligometastatic cancer. Rates of acute and late grade 3 to 5 toxic effects were commonly less than 10%, with clinically acceptable rates of local control, overall survival, and progression-free survival at 1 year post-treatment. Therefore, we recommend that clinicians consider this therapy in selected patients with oligometastatic cancer. Ongoing prospective studies will further explore potential sources of heterogeneity, allowing for a more individualized approach to this therapy.”
— Lehrer et al

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Study Details

The meta-analysis included 21 studies with a total of 943 patients and 1,290 oligometastases published over 15 years through December 2019. The studies includes patients with five or fewer sites of extracranial disease, with SABR being administered in eight or fewer fractions with ≥ 5 Gy/fraction.

Data were analyzed using random-effects meta-analyses. Heterogeneity was assessed using the I2 and τ statistics. The primary outcome measure was the incidence of grade 3 to 5 acute and late toxic effects. The secondary outcome measures were 1-year local tumor control, progression-free survival, and overall survival.

Key Findings

Median follow-up was 16.9 months (interquartile range = 13.7–24.5 months). The most common primary sites were the prostate (22.9%), colon/rectum (16.6%), breast (13.1%), and lung (12.8%).

Across studies, rates of grade 3 to 5 toxic effects ranged from 0% to 20% for acute toxicity and 0% to 10% for late toxicity. Random-effects estimates for the incidence of grade 3 to 5 toxicity were 1.2% (95% confidence interval [CI] = 0%–3.8%; I2 = 50%, 95% CI = 3%–74%; τ = 0.20%, 95% CI = 0.00%–1.43%) for acute toxicity and 1.7% (95% CI = 0.2%–4.6%; I2 = 54%, 95% CI = 11%–76%; τ = 0.25%, 95% CI = 0.01%–1.00%) for late toxicity.

Across studies, 1-year rates ranged from 67.2% to 100% for local tumor control, 33.3% to 80.0% for progression-free survival, and 65.9% to 100% for overall survival. Random-effects estimated 1-year local tumor control was 94.7% (95% CI = 88.6%–98.6%; I2 = 90%, 95% CI = 86%–94%; τ = 0.81%, 95% CI = 0.36%–2.38%). Estimated 1-year progression-free survival was 51.4% (95% CI = 42.7%–60.1%; I2 = 58%, 95% CI = 17%–78%; τ = 0.20%, 95% CI = 0.02%–1.21%). Estimated 1-year overall survival was 85.4% (95% CI = 77.1%–92.0%; I2 = 82%, 95% CI = 71%–88%; τ = 0.72%, 95% CI = 0.30%–2.09%).

The investigators concluded: “In this meta-analysis, SABR appeared to be safe and effective in the setting of oligometastatic cancer. Rates of acute and late grade 3 to 5 toxic effects were commonly less than 10%, with clinically acceptable rates of local control, overall survival, and progression-free survival at 1 year post-treatment. Therefore, we recommend that clinicians consider this therapy in selected patients with oligometastatic cancer. Ongoing prospective studies will further explore potential sources of heterogeneity, allowing for a more individualized approach to this therapy.”

Nicholas G. Zaorsky, MD, MS, of the Department of Radiation Oncology, Penn State Cancer Institute, Hershey, and Eric J. Lehrer, MD, MS, of the Department of Radiation Oncology, Icahn School of Medicine at Mount Sinai, New York, are the corresponding authors of the JAMA Oncology article.

Disclosure: For full disclosures of the study authors, visit jamanetwork.com.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
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