Stereotactic body radiotherapy: a promising treatment for oligometastasis

This article reviewed the role and efficacy of stereotactic body radiotherapy (SBRT) for colorectal cancer-related oligometastasis.

Colorectal cancer may spread from the primary site (colon or rectum) to other organs and tissues of the body. This is referred to as metastasis. Oligometastasis describes an intermediate state of cancer spread, between localized (confined) disease and widespread metastasis.

Stereotactic body radiotherapy involves the delivery of a focused high dose radiation to a well-defined tumor. This reduces the risk of healthy tissue getting damaged by the radiation. This review evaluated the clinical outcomes of stereotactic body radiotherapy for colorectal cancer- related oligometastasis.

This review analyzed a number of studies assessing the effect of stereotactic body radiotherapy for oligometastasis by site of metastasis. Studies of stereotactic body radiotherapy in patients with unresectable liver metastasis (cancer that has spread to the liver and cannot be removed by surgery) showed that the 2-year local control rates were almost over 80%. Two studies with patients treated with high-dose regimens reported the 2-year local control rates of more than 80%. The 2-year overall survival rates varied from 32%-83% with little toxicity.

Studies of stereotactic body radiotherapy in patients with medically inoperable patients with limited pulmonary (lung) metastasis from colorectal cancer showed the local control rates of almost over 80% and the 2-year overall survival rates of between 33% and 86%. Radiation pneumonitis (inflammation of the lungs caused by radiation therapy) was observed in only 0%-8% of patients. In another study that evaluated stereotactic body radiotherapy for isolated lymph node metastasis from colorectal cancer, the 3-year overall survival rate was 71%.

Stereotactic body radiotherapy had 81%-94% local control rates in patients with spinal metastasis. In addition, patients with cancer that has spread to the adrenal glands had a 2-year local control rate of 32% to 90% with differing doses of radiation.

In summary, this review showed that stereotactic body radiotherapy is associated with good clinical outcomes and low morbidity (rate of incidence of a disease) in patients with oligometastasis from colorectal cancer.

This analysis included studies that were performed retrospectively. These studies may have created a slight bias in the presented results.  Further prospective studies are necessary to confirm these findings.