The IMpower 133 trial represented the current SoC in the 1L context for patients with ES-SCLC. Still, more efficacy improvement was needed, such as a 60% objective response rate (ORR) in both arms, which could contribute to a survival advantage. In pretreated ES-SCLC, researchers found that LDRT with ICIs was well tolerated and enhanced effectiveness. The MATCH research was designed to look into the clinical benefits of adding LDRT to Atezo plus chemotherapy in ES-SCLC patients receiving 1L therapy. The MATCH trial was a single-arm phase II experiment in 8 different locations. A two-stage Simon’s minimax design was used. Patients with RECIST v1.1 detectable disease at baseline and an ECOG score of 0-1 were eligible. For 4 cycles, Atezo (1200 mg IV, D1) was combined with Cisplatin (75 mg/m2 IV, D1)/Carboplatin (AUC = 5 IV, D1) +Etoposide (100 mg/m2 IV, D1-D3) on a 21-day cycle. The first cycle included concurrent LDRT (15 Gy/5f) from D1 to D5. The patients were then given Atezo maintenance until they no longer had a therapeutic benefit or experienced unacceptable harm. Investigators confirmed ORR after two consecutive evaluations 4 weeks apart as the primary outcome. Disease control rate (DCR) and safety were the secondary goals. The results of the experiment’s first phase are presented in this report. By the cutoff date of August 26, 2021, 20 of the first 21 evaluable points were males, with a mean age of 60.2 years and an ECOG PS of 1. Previous smokers accounted for 85.7% of the population. T4 (n=15, 71.4%), N3 (n=18, 85.7%), and M1 (n=17, 81.0%) were the most common stages. Bone (47.1%) and liver (47.1%) were the most prevalent sites of metastases (11.8%). The average length of follow-up was 4.0 m. (range: 2.6-8.0 m). The ORR was found to be 95.2% (95% CI, 76.2% -99.9%), with all points being PR. DCR was a perfect 100%. The safety profile was similar to what has been reported in prior reports. The most prevalent grade 3-4 adverse events were a drop in neutrophil count (66.7%), a reduction in white blood cell count (42.9%), and anemia (38.1%). There were no grade 5 AEs. About 2 patients had AEs that caused them to stop taking their medication. About 3 patients (14.3%) had IrAEs: 2 had immune-mediated hyperthyroidism (grade 2), and 1 had immune-mediated enterocolitis (grade 3). There was no radiation pneumonitis. The study satisfied the 1st phase response criteria. In patients with ES-SCLC, a combination of LDRT and Atezo plus chemotherapy showed promise and was acceptable. The second phase was now underway.