Role of radiation in oligometastases and oligoprogression in metastatic non-small cell lung cancer: consensus and controversy

ABSTRACT

Introduction

The oligometastatic state in non-small cell lung cancer (NSCLC) has recently become well-established. However, the specific definition of oligometastases remains unclear. Several smaller randomized studies have investigated the safety and efficacy of radiation as metastasis-directed therapy (MDT) in oligometastatic NSCLC, which have led the way to larger studies currently accruing patients globally.

Areas covered

This review covers the definitions of ‘oligometastases’ and explains why the oligometastatic state is becoming increasingly relevant in metastatic NSCLC. This includes the rationale for MDT in oligometastatic NSCLC, specifically reviewing stereotactic body radiation therapy (SBRT) as a treatment strategy. This review details many randomized trials that support radiation as MDT and introduces trials that are currently accruing patients. Finally, it explores some of the controversies that warrant further investigation.

Expert opinion

Radiation treatment, specifically SBRT, has been shown to be safe, convenient, and cost-effective as MDT. As systemic therapy, including targeted agents and immunotherapy, continues to improve, the precise role(s) and timing of radiation therapy may evolve. However, radiation therapy as MDT will continue to be an integral part of treatment in patients with oligometastatic NSCLC.

KEYWORDS:

• Non-small cell lung cancer
• oligometastasis
• oligoprogression
• metastasis-directed therapy
• SBRT
• SABR
• radiation
• oligometastatic NSCLC

Article highlights

• Oligometastatic NSCLC signifies a clinical state with a limited number of metastases, which may reflect a more indolent biology, and some patients may be cured with a combination of systemic and metastasis-directed therapy.

• Metastasis-directed therapy can include radiation, surgery, or thermal ablation, though radiation has been the most common metastasis-directed therapy evaluated in randomized trials in oligometastatic NSCLC.

• Several small phase 2 randomized trials in oligometastatic NSCLC indicate that metastasis-directed therapy is associated with improved progression-free survival and overall survival.

• The addition of immunotherapy or targeted therapy to metastasis-directed radiation appears to be safe, though some types of systemic agents are associated with higher rates of toxicity when combined with radiation.

• Many phase 3 prospective randomized trials evaluating the role of metastasis-directed therapy in oligometastatic NSCLC are currently open to accrual around the world.

• In addition to improving progression-free and overall, metastasis-directed radiation can improve a patient’s quality-of-life by reducing symptoms including pain, reducing risk of severe symptoms like spinal cord compression, and keeping a patient off systemic therapy.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

This paper was not funded.