AUTHOR=Al-Shafa Faiez , Arifin Andrew J. , Rodrigues George B. , Palma David A. , Louie Alexander V. 

TITLE=A Review of Ongoing Trials of Stereotactic Ablative Radiotherapy for Oligometastatic Cancers: Where Will the Evidence Lead?

JOURNAL=Frontiers in Oncology

VOLUME=9

YEAR=2019

URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2019.00543

DOI=10.3389/fonc.2019.00543

ISSN=2234-943X

ABSTRACT=<p><bold>Purpose:</bold> The oligometastatic state is a proposed entity between localized cancer and widely metastatic disease, comprising an intermediate subset of metastatic cancer patients. Most data to support locally-directed treatment, such as stereotactic ablative radiotherapy (SABR), for oligometastases are from retrospective institutional reports. Following the success of a recently completed and reported phase II trial demonstrating important clinical outcomes, herein we review the current landscape of ongoing clinical trials in this context.</p><p><bold>Materials and methods:</bold> A review of currently activated and registered clinical trials was performed using the clinicaltrials.gov database from inception to February 2019. A search of actively recruiting trials, using the key words oligometastases, SABR, and various related terms was performed. Search results were independently reviewed by two investigators, with discrepancies settled by a third. Data abstracted from identified studies included study type, primary disease site, oncologic endpoints, and inclusion/exclusion criteria.</p><p><bold>Results:</bold> Of the initial 216 entries identified, 64 met our review eligibility criteria after full-text review. The most common study type was a phase II clinical trial (<italic>n</italic> = 35, 55%) with other study designs ranging from observational registry trials to phase III randomized controlled trials (RCTs). A minority of trials were randomized in design (<italic>n</italic> = 17, 27%). While most studies allowed for metastases from multiple primary disease sites (<italic>n</italic> = 22, 34%), the most common was prostate (<italic>n</italic> = 13, 15%), followed by breast, gastrointestinal, non-small cell lung cancer (NSCLC), and renal (<italic>n</italic> = 6, 9% each). In studies with a solitary target site, the most common was liver (<italic>n</italic> = 6, 9%) followed by lung (<italic>n</italic> = 3, 5%). The most common primary endpoints were progression-free survival (PFS) (<italic>n</italic> = 20, 31%) and toxicity (<italic>n</italic> = 10, 16%). A combined strategy of systemic therapy and SABR was an emerging theme (<italic>n</italic> = 23, 36%), with more recent studies specifically evaluating SABR and immunotherapy (<italic>n</italic> = 9, 14%).</p><p><bold>Conclusion:</bold> The safety and efficacy of SABR as oligometastasis-directed treatment is increasingly being evaluated within prospective clinical trials. These data are awaited to compliment the abundance of existing observational studies and to guide clinical decision-making.</p>