374 - Stereotactic Body Radiotherapy Combined with Chemotherapy and PD-1 Inhibitor in Oligometastatic Nasopharyngeal Carcinoma (STOMP): A Prospective Phase II Clinical Trial
Presenter(s)
J. Miao, C. Zhao, H. Mai, X. Lv, L. Tang, Q. Chen, L. Guo, R. Sun, D. Luo, L. Wang, C. Liu, and C. Xiang; Department of Nasopharyngeal Carcinoma, Sun Yat-Sen University Cancer Center, State Key Laboratory of Oncology in South China, Guangdong Key Laboratory of Nasopharyngeal Carcinoma Diagnosis and Therapy, Guangdong Provincial Clinical Research Center, Guangzhou, China
Purpose/Objective(s):
To evaluate the efficacy and safety of stereotactic body radiation therapy (SBRT) combined with gemcitibine plus cisplatin (GP) chemotherapy and PD-1 inhibitor in patients with oligometastatic nasopharyngeal carcinoma (NPC) (NCT05524168).
Materials/Methods:
Main eligibility criteria included diagnosed as oligometastasis NPC (=5 lesions), and have =1 measurable lesion meeting the RECIST 1.1 criteria. Patients firstly receive SBRT for oligometastatic lesions (6-8Gy/fraction × 3-5 fractions), then receive GP+PD-1 inhibitor for 4-6 cycles followed by PD-1 inhibitor maintenance for 1 year. For patients with primary metastasis, the primary lesion and regional metastatic lymph nodes are given radiotherapy (RT) after completing 4-6 cycles of GP+PD-1 inhibitor. The primary endpoint was the 1-year progression-free survival (PFS) rate.
Results:
Between Nov 2022 to Jun 2025, 41 oligometastasis patients were recruited (Table 1). 23 patients were primary metastases, and 17 had distant metastasis (DM) after receiving chemo-radiotherapy, and 1 had regional relapse and DM. All patients finished SBRT for metastatic lesions followed by GP+PD-1, and 23 patients with primary metastasis also received RT for primary lesions. Then 17 received =1 year PD-1 maintenance, 3 discontinued for PD, 1 requested to withdraw, and 20 still under PD-1 maintenance. With the median follow-up time of 17.3 months, all these metastatic lesions receiving SBRT controlled well; 7 patients had disease progression, including 1 regional relapse, 4 DM, and 2 loco-regional relapse and DM, and all these lesions were newly developed metastatic lesions except one regional relapse which didn’t receive SBRT. The primary endpoint 1-year PFS rate was 92.2% (95%CI, 77.6-97.4%), and the secondary survival endpoints 1-year OS, DMFS and LRRFS rate were 100.0% (95%CI, 100-100%), 92.2% (95%CI, 77.6-97.4%), and 97.5% (95%CI, 83.5-99.6%), respectively. The best objective response rate (ORR) and disease control rate (DCR) before starting PD-1 maintenance were 92.7% and 100%, with 27 got complete response, 11 got partial response and 3 got stable disease. The most common grade 1-2 adverse events (AEs) relating chemo-immunotherapy were fatigue (100%), nausea (100%), and anorexia (100% ); the most common grade 3-4 AEs were leukopenia (56.1%), neutropenia (51.2%), and thrombocytopenia (46.3%). The AEs relating SBRT were grade 1, including radiation hepatitis (9.8%), pneumonia (4.9%), enteritis (2.4%), and brachial plexus neuropathy (2.4%). No grade 5 AEs was observed in this trial.
Conclusion:
Patients with oligometastatic NPC who receive SBRT for metastatic lesions combined with GP and PD-1 inhibitor could achieve good therapeutic effects with acceptable toxicities.
Table 1 Basic information.
| Characteristic | N (%) | |
| Median age (IQR), year | 48 (39-54) | |
| Sex | Female | 13 (31.7) |
| Male | 28 (68.3) | |
| ECOG, points | 0 | 4 (9.8) |
| 1 | 37 (90.2) | |
| Number of metastases lesions | 1-2 | 33 (80.5) |
| 3-4 | 8 (19.5) | |
| Number of metastases organs | 1 | 31 (75.6) |
| 2 | 10 (24.4) | |