The role of SBRT as a potentially non-invasive treatment for small-volume tumors in the lung is well established, but the effectiveness of tumor eradication has yet to be determined. This prospective Phase 2 trial will provide several novel contributions to the literature: 1) the assessment of SBRT effectiveness in metastatic tumor control (radiotherapeutic metastasectomy), 2) the evaluation of pathologic response to SBRT by surgical resection, 3) identification of histologic predictors of radiation effect and toxicity (i.e. what are the effects of SBRT on different type of metastatic disease), and 4) the effect of combined modality SBRT and surgery on survival and local recurrence as compared to either modality alone. This trial will uniquely assess whether surgery as an adjunct to radiotherapy offers better tumor control as compared to SBRT alone, and whether it decreases locoregional recurrence. The study is an open-label unblinded single-arm prospective trial evaluating induction SBRT followed by pulmonary metastasectomy. This is a collaborative effort between the divisions of Thoracic Surgery and Radiation Oncology to evaluate the effects of dual treatment of pulmonary metastasis amenable to curative resection with neoadjuvant SBRT followed by surgical resection. Study recruitment and analysis will be conducted at St. Joseph Healthcare Hamilton and the Juravinski Cancer Center. Institutional data suggests that the Division of Thoracic Surgery at McMaster University performs an average of 450 pulmonary resections per year with approximately 10-15% being pulmonary metastasectomies for a spectrum of malignancies (including colorectal carcinoma, renal cell carcinoma and soft tissue sarcoma).

Surgical resection and stereotactic body radiation therapy (SBRT) are generally regarded as mutually exclusive treatment options for the local management of pulmonary malignancies. The Primary Outcome will be measured as the Rates of complete pathologic response (pCR) in surgical specimens post SBRT as assessed using the Junker grading scale for lung malignancies: Grade I, no regression or only spontaneous tumor regression; Grade II, morphologic evidence of tumor regression with at least 10% (grade IIa) or \<10% (grade IIb) viable tumor tissue; and Grade III, complete tumor regression with no viable tumor. The Secondary Outcomes: Overall survival (OS) at 3 years, Disease-free survival (DFS) at 3 years, local recurrence rates, radiation related toxicity, postoperative pulmonary complication rate (including prolonged air leak, need for invasive or noninvasive mechanical ventilation, postop pneumonia and empyema), the effect on time-to-resection and tumour histology on pCR. In addition, it will be explored whether cancer specific tumor biomarkers correlate with SBRT effects and related toxicity. Based on institutional data from other local prospective trials, the Thoracic Surgery division at McMaster averages a study accrual rate of 25-30% and retention rate of approximately 80%. The most pertinent metric in determining the necessary sample size is the effect size estimate of pCR. The MISSILE study preliminary data demonstrated a pCR of 60%. This serves as the only representative value in the literature, even though our study evaluates SBRT and surgery for metastatic disease and NOT primary lung cancer. In contrast, the SBRT literature (using post-treatment CT scan surveillance only) reports local control rates of nearly 90%. Using the Fleming procedure, in order to measure the true pCR with a 95% confidence interval ± 10% using an estimated true pCR of 70%, estimated dropout rate of 20%, and 80% power, the calculated sample size requirement is 39 patients. It is estimated being able to recruit approximately 1-2 patients per month.