Stereotactic body radiotherapy (SBRT) in the management of extracranial oligometastatic (OM) disease

Objective:

A review of stereotactic body radiotherapy (SBRT) for oligometastases defined as three or fewer sites of isolated metastatic disease. The aim was to identify local control, overall survival (OS) and progression-free survival (PFS) of patients receiving SBRT for oligometastatic (OM) disease.

Methods:

Data were analysed for SBRT delivered between 01 September 2010 and 31 March 2014. End points included local control, PFS, OS and toxicity.

Results:

76 patients received SBRT. The median age was 60 years (31–89 years). 44 were male. Median follow-up was 12.3 months (0.2–36.9 months). Major primary tumour sites included colorectal (38%), the breast (18%) and the prostate (12%). The treatment sites included lymph nodes (42%), the bone and spine (29%) and soft tissue (29%). 42% were previously treated with conventional radiotherapy. 45% were disease free after SBRT. 4% had local relapse, 45% had distant relapse, and 6% had local and distant relapse. Local control was 89%. The OS was 84.4% at 1 year and 63.2% at 2 years. PFS was 49.1% at 1 year and 26.2% at 2 years. Toxicities included duodenal ulcer and biliary stricture formation.

Conclusion:

SBRT can achieve durable control of OM lesions and results in minimal radiation-induced morbidity.

Advances in knowledge:

This cohort is one of the largest reported to date and contributes to the field of SBRT in oligometastases that is emerging as an important research area. It is the only study reported from the UK and uses a uniform technique throughout. The efficacy and low toxicity with durable control of local disease with this approach is shown, setting the foundations for future randomized studies.Stereotactic body radiotherapy (SBRT) allows us to deliver ablative doses of radiation to extracranial sites, and this treatment modality can be considered in the setting of oligometastatic (OM) disease. Traditionally, systemic agents have been the mainstay of the management of metastatic disease, however, we have entered an era where in certain settings long-term local control or cure can be achieved. The idea of an OM state (defined as 1–3 isolated metastatic deposits) was first proposed in 1995 by Hellman and Weichselbaum¹ when they suggested that for many cancers, a few metastases exist at first, before the malignant cells acquire widespread metastatic potential. Following this, Niibe and Hayakawa² described the concept of oligorecurrence that whilst similar to oligometastases has control of the primary site of the malignancy allowing local therapies to achieve control of metastatic sites. Radical treatment of oligometastases and/or oligorecurrences may therefore achieve local control or cure in carefully selected cases. Local therapies including surgical resection, irradiation and radiofrequency ablation are radical treatment options to achieve this.^1,2 Local control rates of 80% have been achieved from several non-randomized studies of SBRT for oligometastases, and SBRT has been shown to be safe and effective.³