Oligometastasis: Expansion of Curative Treatments in the Field of Oncology

Abstract

Oligometastasis is defined as the presence of several limited metastatic lesions and is generally limited to three or fewer than five metastatic lesions. Previously, the treatment of metastatic cancer aimed to alleviate symptoms rather than cure them; however, the use of immunotherapy or targeted therapy has greatly improved patient life expectancy. Additionally, the effectiveness and safety of local treatment have recently been proven for oligometastatic cancers and have significantly improved patient survival and decreased recurrence rates. A few metastatic studies on lung cancer have demonstrated the usefulness of combining radiation therapy and immunotherapy. Recently, local and targeted therapy combinations have shown promising results in treating non-small cell lung cancer, predominantly caused by the epidermal growth factor receptor and anaplastic lymphoma kinase gene mutations, suggesting the potential of these new treatment strategies. It is well known that oligometastasis has better clinical results than polymetastasis; however, research on the biological profile of oligometastasis is still lacking. Studies using circulating tumor DNA and circulating tumor cells are at the initial stages of providing a better understanding of oligometastatic cancers, and the biological characteristics of these cancers may be revealed based on more diverse studies. With the development of these treatments, the prognosis for patients with oligometastatic cancers is steadily improving, and if the biological profile is revealed, customized treatment may be provided.

Keywords: immunotherapy; local treatment; lung cancer; oligometastasis; oligometastatic cancer; radiation therapy; surgery; targeted therapy.

Figure 1

(Left) Definition of oligometastasis in studies included in systematic literature analysis, (Middle) studies of oligometastasis, (Right) treatment methods used as local treatment by study. (Figure adapted from Rim et al. [1]. Role of Local Treatment for Oligometastasis: A Comparability Based Meta-Analysis. Cancer Research and Treatment. 2022. Figures redrawn by authors.)

Figure 2

A case of long-term survival obtained by combining local and systemic treatment for oligometastasis. A 60-year-old male patient with multiple small HCC had stable disease for 2 years after trans-arterial chemoembolization. A metastatic nodule (oligorecurrence) was discovered in lung RML, and 55 Gy/5 F SBRT was performed. Remission was achieved at 3 months, and complete remission was achieved at 2 years. Regorafenib was maintained for another 5 years, after performing SBRT, and stable disease was maintained. (upper) Sequential image after SBRT; (lower) treatment planning of SBRT. The right lower figure shows dose-volume distribution of, from the right, tumor (red), tumor with margin (cyan), right lung (green), heart (magenta), and esophagus (pink). The large gap between dose graphs of tumor target and normal organs such as lung or heart, denotes potent treatment efficacy with small possibility of toxicity. SBRT, stereotactic body radiotherapy; HCC, hepatocellular carcinomas.