Abstract 1396P
Background
In this exploratory analysis from the PRODIGY study, we aimed to define the radiological criteria to identify patients with gastric cancer who may derive maximal clinical benefit from neoadjuvant chemotherapy.
Methods
There were 246 patients allocated to receive surgery followed by adjuvant S-1 (SC group) and 238 allocated to receive additional neoadjuvant chemotherapy (CSC group). cT stage was assessed based on the invasion depth by computed tomography (CT). As the PRODIGY study’s radiological method of lymph node evaluation by CT considers short diameter and morphology (the size and morphology method), a method considering only short diameter (size-only method) was also employed. In the SC group, the correlation between radiologic and pathologic findings was analyzed. The hazard ratio (HR) for the progression-free survival (PFS) of the CSC group was analyzed in subgroups with different cT/N stages.
Results
While the overall concordance rate between clinical and pathological T staging was 48.2%, cT4 disease showed a sensitivity of 85.6% for detecting pT4 and it was associated with a low proportion of pathologic Stage I disease (≤ 5.6%). Among the criteria determined by different cT/N stages by each method of lymph node positivity, those involving cT4Nany or cT4N+ by both methods had a minimal proportion of pathologic stage I disease (≤ 5%), while cT4Nany by both methods and cT4N+ by the size and morphology method exhibited a sensitivity for detecting pathologic Stage III disease of ≥ 75.9%. The relative risk reduction in PFS of the CSC group was the greatest in patients meeting the cT4Nany criterion defined by both methods (HR 0.68, 95% confidence interval 0.50–0.94).
Conclusions
The cT4Nany criterion, regardless of the radiological method used for lymph node evaluation, may help select patients with resectable gastric cancer for neoadjuvant chemotherapy.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
Y. Kang: Other, Personal, Advisory Role: ALX Oncology; Other, Personal, Advisory Role: Amgen; Other, Personal, Advisory Role: BMS; Other, Personal, Advisory Role: Blueprint; Other, Personal, Advisory Role: Daehwa; Other, Personal, Advisory Role: Macrogenics; Other, Personal, Advisory Role: Merck (MSD); Other, Personal, Advisory Role: Novartis; Other, Personal, Advisory Role: Surface Oncology; Other, Personal, Advisory Role: Zymeworks. All other authors have declared no conflicts of interest.