Stereotactic Body Radiotherapy for Early-Stage Non–Small-Cell Lung Cancer: American Society of Clinical Oncology Endorsement of the American Society for Radiation Oncology Evidence-Based Guideline Summary

More than 155,000 estimated deaths will be attributable to non–small-cell lung cancer (NSCLC) in the United States in 2017, making it the leading cause of cancer death for both men and women.1 Approximately 16% of new cases will be early-stage localized tumors.2,3 According to the 7th edition of the American Joint Committee on Cancer staging system, these are T1 or T2 tumors with no regional lymph node or distant metastases.4 Early-stage NSCLC has historically been treated with lobectomy5 and mediastinal/hilar lymph node sampling,3 while sublobar resection may be an option for patients with low pulmonary reserve and early-stage lung cancer.6 In cases where patients are not fit or healthy enough to be candidates for surgery, or where surgery is declined, alternative effective treatment options are desirable. Historical attempts to use conventionally fractionated radiation therapy in this scenario have met with limited success in terms of local control due to difficulties with delivering an effective dose and high rates of toxicity because of limited ability to define and constrain treatment volumes with this technique.3 For these reasons, stereotactic body radiation therapy (SBRT), also known as stereotactic ablative radiation therapy, defined as “a strategy that employs very high (ie. ablative) doses of radiation delivered to the cancer target over 1-5 fractions with highly conformal techniques”3(p1) emerged as a treatment option. In the Radiation Therapy Oncology Group (RTOG) 0236 phase II trial of SBRT in inoperable patients with peripheral tumors ≤ 5 cm, 5-year estimates of primary tumor, involved-lobe, and locoregional failure were 7%, 13%, and 38%, respectively, after a median follow-up of 4 years.7 Due to difficulties with accrual, no phase III randomized controlled trials comparing SBRT with surgical resection have been completed to date; however, SBRT is already widely used for early-stage peripherally located inoperable lung cancer8 and has shown encouraging results in patients who are not fit or healthy enough to undergo surgery.5 The American Society of Radiation Oncology (ASTRO) has developed an evidence-based guideline for the use of SBRT in patients who are considered to be at standard operative risk and high operative risk and those who present with more clinically challenging scenarios in terms of tumor size or location, as well as patient cases without tissue diagnosis or tumors that are synchronous primary or multifocal, second primary after pneumonectomy, or recurrent after previous treatment.3 The ASCO Expert Panel critically