Stereotactic body radiationtherapy (SBRT), also known as stereotactic ablative radiotherapy (SABR). Early stage lung cancer has become the main model for clinical trials of this technology. Since its inception in the mid-1990s, SBRT has distinguished itself among the most radical treatments for most tumors by its unique advantages of high tumor control rates, good normal tissue tolerance, long patient survival, and extreme convenience. every other day. Each treatment takes between 20-60 minutes from patient positioning to treatment completion, and the entire treatment can be completed within 1-2 weeks. The majority of patients return to normal life immediately after treatment. Unlike conventional fractionated radiotherapy (1.8-2.5 Gy per day) or large fractionated radiotherapy (3-6 Gy per day, often used for terminal palliative care), SBRT can be performed at ablative doses of up to 8-30 Gy per day with the support of sophisticated image-guided techniques. Such high doses can disable the tumor repair mechanisms that lead to the failure of other treatments, but with the potential risk of severe late reactions that cannot be tolerated. The key to ensuring successful treatment is strict caution in treatment delivery, along with aggressive symptomatic supportive therapy. Early clinical trial of SBRT for inoperable lung cancer RTOG 0236 is the first multicenter trial in North America of SBRT for clinically inoperable early-stage lung cancer. The prescribed dose to tumors is 20 Gy x 3 = 60 Gy on a water-equivalent basis, which is equivalent to 18 Gy x 3 = 54 Gy when tissue heterogeneity is taken into account. RTOG 0236 also has strict technical procedures for SBRT implementation, strict dose controls for normal tissue, and a quality management system that includes accreditation of treatment centers. The trial also played an important role in providing training for many treatment centers on how to set up SBRT treatment programs according to RTOG’s clinical treatment guidelines. RTOG 0236 trial started in 2004, treating 57 patients and completing patient enrollment in 2006. Clinical outcomes were quite favorable: 98% primary tumor control at 3 years and a 56% survival rate. As the trial results matured, the 18 Gy x 3 treatment dose pattern became the standard for RTOG clinical trials for unresectable peripheral lung cancer SBRT treatment. Central lung cancer was excluded from the enrollment of RTOG0236 due to the higher complication rate in cases of central lung cancer treated with SBRT at Indiana University. It is now recognized that tubular structures such as the trachea, hilar vessels, and esophagus are more susceptible to toxic side effects when treated ablatively. RTOG is currently conducting a phase I clinical trial of SBRT for central lung cancer (RTOG 0813, lead: Andrea Bezjak). This trial is a phase I/II dose creep study, starting with a total dose of 10 Gy x 5 = 50 Gy, to test the idea that increasing the number of radiotherapy fractions may reduce toxic side effects. The goal of the study is to develop an effective and feasible dose regimen for future clinical trials. This trial requires an accurate assessment of the effect of tissue heterogeneity on dose and requires the application of IMRT techniques to avoid tubular structures such as the trachea and esophagus whenever possible. This clinical trial, conducted by Indiana University, is one of the first studies to demonstrate a dose-effect relationship in local control of lung cancer and may have a longer follow-up and richer data than other similar prospective studies. Although local control rates increased with increasing dose, there was no significant difference in survival; whereas for patients who underwent surgical resection, increased local control rates were usually accompanied by improved survival. Retrospective data analysis showed that almost half of the untreated inoperable patients ultimately died from other concurrent disease rather than the tumor itself. Thus, the Indiana University results may reflect the characteristics of patients who choose to be treated with SBRT, i.e., the presence of disease that renders them unfit for surgery, and the fact that patients are often weaker than those treated surgically. So, for patients with inoperable lung cancer, which factor is more important in influencing survival: avoiding death from non-small cell lung cancer or other co-morbidities/complications? RTOG 0915, a phase II randomized clinical trial of peripheral lung cancer, is a first step in exploring the answer to this question. This trial compared 2 published SBRT regimens, both using lower doses than RTOG 0236, with the primary observation being toxicities. After completion of the RTOG 0915 trial, the next step will be to compare the less toxic of the two regimens with the RTOG 0236 standard dose regimen in a phase III clinical trial. Given that a 3-year local control rate of 98% was already achieved with the standard dose regimen, it is difficult to expect further improvement in tumor local control with RTOG 0915, but it may be more beneficial in less fit patients. This clinical trial design may not be suitable for surgically treatable cases where improved tumor resection rates would help improve patient survival. Application of SBRT to surgically resectable lung cancer The results of SBRT in inoperable lung cancer have shown that it is effective in eliminating the primary tumor and is well tolerated in this high-risk population. In view of this, the possibility of its application in patients with operable lung cancer has received attention. In Japan, patients with lung cancer who refuse surgical treatment have been treated with SBRT. With a reasonable dose of irradiation, SBRT treatment can achieve an efficacy comparable to that of surgical resection, even lobectomy. RTOG has initiated a preclinical trial, RTOG0618, to evaluate the efficacy of SBRT in patients with operable lung cancer using the dosing regimen of RTOG 0236. In this trial, an adequate dose of radiotherapy is key to treatment success, as surgical treatment as a control is well established and highly competitive in this group of lung cancer patients, with control rates of lobectomy of more than 90%. The primary goal of the trial was a 2-year local control rate of 90%, with secondary goals of survival and toxic side effects. In these patients, the local control rate is the most important prognostic factor; the trial requirements are met if RTOG 0618 achieves a local control rate similar to that of RTOG 0236 using the same treatment regimen. Two trials have been initiated in which patients with operable lung cancer are randomly assigned to receive either surgery or SBRT, and both trials are currently in the patient enrollment phase.