Stereotactic Radiotherapy for Oligometastases in Lymph Nodes—A Review

Abstract

In recent years, the concept of oligometastases has become accepted and reports on stereotactic body radiotherapy as a treatment method have been published. Lesions in the brain, lung, and liver have been reported as target lesions. However, lymph node oligometastases could be a good candidate for stereotactic body radiotherapy as well. In this study, the usability of stereotactic body radiotherapy for oligometastases to lymph nodes is assessed by researching for each primary site. As a result, we could consider that stereotactic body radiotherapy could be almost well applied for lymph node oligometastases from the breast, gynecological organs, and prostate. However, doubts remain concerning the usefulness of stereotactic body radiotherapy for cervical node metastases from head and neck cancer or for mediastinal node metastases from lung or esophageal cancer since late toxicities have occurred with a large radiation dose at hypofractionation to major vessels or the central respiratory tract, especially in patients with irradiation histories. In addition, high-dose irradiation is required to control lymph node metastases from colorectal cancer due to its radioresistance, and severe late adverse events would therefore occur in adjacent organs such as the gastrointestinal tract. In cases of lymph node oligometastases with a primary tumor in the stomach or esophagus, stereotactic body radiotherapy should be used limitedly at present because this patient population is not so large and these metastases are often located close to organs at risk. Because of the varied status of recurrence and varied conditions of patients, it is difficult to determine the optimal dose for tumor control. It might be reasonable to determine the treatment dose individually based on dose constraints of adjacent organs. The oligometastatic state is becoming more frequently identified with more sensitive methods of detecting such oligometastases. In addition, there seems to be another type of oligometastases, so-called induced oligometastases, following successful systemic treatment. To determine the optimal indication of stereotactic body radiotherapy for lymph node oligometastases, further investigation about the mechanisms of oligometastases and further clinical studies including a phase III study are needed.

Radiation Therapy in Adult Soft Tissue Sarcoma—Current Knowledge and Future Directions: A Review and Expert Opinion

“…Generally, SRS or SBRT can be used also for metastases in different body regions, for example liver, brain, lymph nodes, or soft-tissue metastases. Several prospective trials and large retrospective series have established its role especially in brain metastases, liver metastases and (to a lesser extent) for lymph node metastases [92][93][94], consistently showing high local control rates with low toxicity. Due to the relative rarity of STS per se, most of these reports include only a minority of STS cases and very rare data on SBRT specifically addressing STS metastases has been published so far.…”

Oligometastatic Breast Cancer: How to Manage It?

“…Oligorecurrent metastases in the brain, lung, and liver can be definitively treated with SBRT. Instead, there are some controversies regarding lymph node oligometastases, thus further phase III trials are needed [42].…”

“…The research is moving forward, with an ongoing randomized phase II/III trial (NRG-BR002), which evaluates the role of these techniques in OMBC [42,52].…”

Online Magnetic Resonance-Guided Radiotherapy (oMRgRT) for Gynecological Cancers

“…Isolated lymph node metastases from gynecologic malignancies are considered a good indication for SBRT, as they usually occur within the pelvis or the PAO lymph node region (64,65). SBRT can be applied in the setting of limited oligometastatic disease, with the aim of postponing or enhancing systemic therapies, or as an alternative to surgical resection (66).…”

“…The effectiveness of SBRT on LC is clearly associated with a doseresponse correlation; higher biologically equivalent dose (BED) leads to better tumor control (71,72). For lymph node metastases, 5year LC rates of uterine, cervical, and ovarian cancer range from 70 to 97%, and favorable disease-free survival and overall survival are reported in retrospective series (64,68,70,(72)(73)(74)(75)(76)(77). Lymph node metastases of gynecologic malignancies are often located in the pelvis or abdomen, where conventional SBRT using CBCT image guidance yields relatively poor soft tissue contrast.…”