Influence of neoadjuvant regimen on the prognosis of locally advanced gastric and gastroesophageal junction cancer with HER2 overexpression.

Abstract

e16082 Background: The relative high recurrence rate in locally advanced gastric or gastroesophageal junction (G/GEJ) cancer with Her2 overexpression after surgery, along with the absence of a standard neoadjuvant treatment protocol, necessitates exploration of novel approaches for this patient population. Methods: In this study, we conducted a retrospective analysis of clinical characteristics, postoperative pathological results, and survival data for patients who underwent neoadjuvant treatment and subsequent surgery at our center from September 2020 to December 31, 2022. The inclusion criteria were as follows: 1) pathologically confirmed adenocarcinoma of the G/GEJ; 2) diagnosed as cT3-4 or N+ by enhanced CT and endoscopic ultrasound; 3) Her2 immunohistochemistry 3+ or 2+ with Fish positive in biopsy specimens; 4) discussed in a multidisciplinary team for the need for neoadjuvant treatment; 5) received 2-4 cycles of neoadjuvant therapy; 6) underwent radical D2 surgery; 7) had complete follow-up data. Results: Seventy-three patients met the inclusion criteria, with 19 receiving chemotherapy + anti-PD-1, 10 receiving chemotherapy + anti-Her2, and 44 receiving chemotherapy alone. Their pCR rates were 31.6%, 10%, and 2.3%, respectively (P = 0.003); MPR rates were 42.1%, 30%, and 11.4% (P = 0.022). As of the last follow-up on December 31, 2023, the median DFS for the chemotherapy group was 18.1 months (95% confidence interval 14.9-21.3); median DFS for the other two groups had not been reached. DFS analysis revealed differences in median DFS among different neoadjuvant treatment regimens (P = 0.025); further pairwise comparisons indicated that this difference mainly stemmed from the chemotherapy + anti-Her2 group compared to the chemotherapy group. Conclusions: In locally advanced gastric and gastroesophageal junction cancer with Her2 overexpression, neoadjuvant chemotherapy combined with anti-Her2 treatment improves the pCR rate and prolongs DFS compared to neoadjuvant chemotherapy alone.