Abstract 70P
Background
Although immune checkpoint inhibitors (ICIs) have improved the outcome for many cancers, the response rate of PD-1 inhibitors alone is not ideal. Hypofractionated radiotherapy (HFRT) and ICI together is a particularly promising combination therapy. With the help of GM-CSF and Thymosin α1, the combination has the potential to expand the beneficiary population and increase survival gains.
Methods
This clinical trial was conducted in 11 hospitals in China and enrolled 36 participants between September 2022 to March 2024. 1-4 tumor lesions of enrolled patients received HFRT (24-56 Gy/4-10 Gy), GM-CSF (150 μg, Qd*14d) on the day of radiotherapy, and thymosin α1 for injection (1.6 mg, BIW) was administered until disease progression or the study reached the endpoint of termination. The PD-1 inhibitor (q3W) was initiated within 1 week after the completion of radiotherapy and GM-CSF (150 μg, Qd*7d) was administered one week before the PD-1 inhibitor treatment. The primary endpoint was progression-free survival (PFS). Secondary end points included objective response rate (ORR), disease control rate (DCR), and toxic effects. Efficacy was assessed in the intention-to-treat (ITT) population, while safety was evaluated in the as-treated population.
Results
Until March 31, 2024, a total of 36 patients were enrolled in this study and the median follow-up time was 9.0 (0.7-17.1) months. In ITT patients, the median PFS was 3.5 months (95%CI: 2.77-4.23m). ORR was 23.08% and DCR was 73.08%. OS data is not yet mature. 16 adverse reactions were reported, including 3 cases of grade 3 or 4 adverse events. No grade 5 adverse events occurred. Table: 70P
| ORR | DCR | PFS (95%CI) | |
| Enrolled patients | 21.43% | 71.43% | 3.33m(2.51-4.15) |
| ITT Patients | 23.08% | 73.08% | 3.50m(2.77-4.23) |
| Pior ICI Patients | 18.18% | 72.73% | 3.17m(2.52-3.82) |
| No Pior ICI Patients | 26.67% | 73.33% | 3.70m(1.56-5.84) |
Conclusions
This clinical trial has demonstrated good efficacy and the safety was ensured. HFRT combined with immunotherapy, GM-CSF, and thymosin α1 combination therapy may offer new hope to patients with advanced recurrent metastatic solid tumors.
Clinical trial identification
ChiCTR2200062706, Release date: 2022-08-16.
Editorial acknowledgement
Legal entity responsible for the study
Jiangsu Cancer Hospital.
Funding
National Natural Science Foundation of China (82172804).
Disclosure
All authors have declared no conflicts of interest.