Robotic Stereotactic Body Radiotherapy Beneficial for Oligorecurrent Lung Metastases

A recent study explored the effect of robotic stereotactic body radiotherapy (SBRT) in patients with oligorecurrent lung metastases (ORLM).

“Resection of lung metastases (metastasectomy) has become a widespread and accepted standard therapy. However, evidence for pulmonary metastasectomy is weak as no randomized clinical trials exist to support its benefit. In case of oligometastatic lung disease (OMLD), less invasive interventions such as radiofrequency- and microwave ablation and stereotactic body radiotherapy (SBRT) have been described as a valid alternative to surgery,” the study authors explained.

“The major challenge when delivering SBRT to lung metastases is to manage respiratory motion of both tumor and normal tissues. Breathing control strategies such as breath-hold, gating, tumor tracking and motion management techniques have been implemented to deal with this challenge. One of those strategies is the Cyberknife® synchrony (Accuray Inc., Sunnyvale, CA), which performs real-time tumor tracking. This allows for a high level of precision while treating the patient in the comfort of free breathing.”

To conduct their study, patients with up to five ORLM underwent SBRT with the Cyberknife®. The intended dose was 60Gy in 3 fractions, which was prescribed to the 80% isodose volume. Tumor control and toxicity were evaluated. Outcomes included the effect of tumor-, patient-, and treatment-related parameters on local control (LC), and lung and distant progression free- (lung PFS/Di-PFS) and overall survival (OS).

A total of 104 ORLM patients (132 lesions) between May 2010 and March 2016 were retrospectively reviewed. Lesions were irradiated from primary lung carcinoma (47%) as well as gastro-intestinal (GI) (34%) and mixed primary histologies (19%); tumors had a mean 7.9 cc volume. Median follow-up time was 22 months. The one-year LC rate (per lesion) was 89.3%, the two-year rate were 80.0%, and the three-year rate was 77.8%, respectively; at the same time points, the per patient lung PFS were 66.3%, 50.0%, and 42.6%, respectively; DiPFS, 80.5%, 64.4%, and 60.6%, respectively; and OS, 92.2%, 80.9%, and 72.0%, respectively. univariable analysis found that when GI was the primary tumor site, compared to other primary tumor sites, local control was significantly better. OS outcomes were correlated with primary histology and primary tumor site; patients whose metastases had primary GI origin had superior OS. Factors associated with LC were tumor volume and physical and biologically effective dose coverage. Upon multivariable analysis, BED prescription dose was correlated with LC and GI as the primary site with OS. Most patients had no toxicity or grade 1 acute and late toxicity; one and two patients each experienced acute and late grade 3 radiation pneumonitis (RP), respectively. One patient who had a centrally located lesion and grade 4 RP died; the death was attributed to possible RT-induced pulmonary hemorrhage.

The study appeared in BMC Cancer.

“In conclusion, SBRT as delivered in this study is a highly effective local therapy for the treatment of de-novo metachronous-and repeat [ORLM] and might be able to sterilize a limited number of lesions and achieve long term survival rates in patients with more favourable prognostic features,” summarized the authors.