Stereotactic body radiotherapy combined with chemotherapy and PD-1 inhibitor in oligometastatic nasopharyngeal carcinoma (STOMP): A prospective phase II clinical trial.

Abstract

232 Background: 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), registered on clincialtrials.gov (NCT05524168). 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 NPC 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 after 6 cycles of GP+PD-1. 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 (IQR, 12.9-21.8) 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 median value of EBV DNA copies pretreatment was 743 (IQR, 151.5-5331.0) copies/ml, then decreased to 0 (IQR, 0-0) copies/ml post 6 cycles of GP+PD-1. No grade 5 therapeutic toxicity was observed in this trial. Conclusions: 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. Clinical trial information: NCT05524168 . 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)