Stereotactic radiotherapy in oligometastatic cancer

Abstract

Oligometastatic cancer describes a disease state somewhere between localized and metastatic cancer. Proposed definitions of oligometastatic disease have typically used a cut-off of five or fewer sites of disease. Treatment of oligometastatic disease should have the goal of long-term local control, and in selected cases, disease remission. While several retrospective cohorts argue for surgical excision of limited metastases (metastasectomy) as the preferred treatment option for several clinical indications, limited randomized data exists for treating oligometastases. Alternatively, stereotactic ablative radiotherapy (SABR) is a radiotherapy technique that combines high radiation doses per fraction with precision targeting with the goal of achieving long-term local control of treated sites. Published cohort studies of SABR have demonstrated excellent local control rates of 70-90% in oligometastatic disease, with long-term survival in some series approaching 20-40%. A recent randomized phase 2 clinical trial by Gomez et al. demonstrated significantly improved progression free survival with aggressive consolidative therapy (surgery, radiotherapy ± chemotherapy or SABR) in oli-gometastatic non-small cell lung cancer (NSCLC). As additional randomized controlled trials are ongoing to determine the efficacy of SABR in oligometastatic disease, SABR is increasingly being used within routine clinical practice. This review article aims to sum-marize the history and current paradigm of the oligometastatic state, review recently pub-lished literature of SABR in oligometastatic cancer and discuss ongoing trials and future directions in this context.

Oligometastases in head and neck carcinoma and their impact on management

“…Kennedy et al documented that SABR offers 70-90% local control of oligometastatic disease with long-term survival reaching 20-40%. 70 Widder et al conducted a study comparing stereotactic radiotherapy and pulmonary metastasectomy in 110 patients with solid tumours and reported the OS rates at 1, 3 and 5 years were 87%, 62% and 41% for pulmonary metastasectomy, and 98%, 60% and 49% for SABR, respectively. 71 Currently, SABR is not recommended for cervical lymph node OMs in patients with head and neck cancer due to the risk and morbidity to adjacent tissue such as the carotid artery.…”

Fiducial marker implantation using convex probe EBUS and autologous blood

“…Stereotactic body radiotherapy (SBRT) has evolved as an improved treatment strategy for early-stage lung cancer in individuals who are unfit for surgery1 and for oligometastatic disease 2. Precision targeting of small lesions for high-dose radiation is key.…”

Abscopal effects induced by localized interventions in oncological patients.

“…Over the decades, the energy and intensity of the incident radiation were remarkably enhanced, while the delivered dose was sharply restricted to the target, in order to reduce the detrimental side effects in healthy tissues and organs. To this end, more selective techniques have been developed, such as stereotactic ablative radiotherapy (SABR) and stereotactic radiosurgery (SRS) that are regulated with high precision either by computed tomography (CT)-, or magnetic resonance imaging (MRI)-based imaging systems (19)(20)(21), which allow for a more selective detection and destruction of small tumor masses, such as oligometastases and early-stage malignancies (19,(22)(23)(24)(25)(26)(27)(28). Interestingly, the radiation beam may also affect tissues and/or cells that are external to the irradiated target (18,21).…”