Ampullary cancer, a rare malignancy, lacks standardized guidelines for effective multimodal treatment following curative resection. The opinions on whether postoperative chemotherapy can improve the long-term survival of ampullary adenocarcinoma (AA) are discordant. This aspect remains poorly studied, with comparably scant research conducted on it.

log odds of positive lymph nodes (LODDS), a quantitative variable, can continuously and accurately reflect the burden of nodal involvement, which suggested a potential ability to identify AA patients benefiting from postoperative adjuvant chemotherapy (ACT). Therefore, Mainly focused issues of ACT addressed in the study are as follows: 1) the role of ACT in improving long-term survival for patients with AA after curative resection. 2) the role of LODDS in identifying postoperative AA patients benefiting from ACT. 3) compared with T and N classifications reported previously, the advantage of LODDS in identifying ACT-benefited patients.

In this cohort study, a large scale of sample size was conducted by drawing on the collective experience of the National Cancer Center of China. The patients treated with radiotherapy were excluded to concentrate on the effect of ACT.

Inclusion Criteria:

Pathologically confirmed AA patients without distant metastasis treated with curative-intent resection

Exclusion Criteria:

patients who received neoadjuvant therapy or radiotherapy, as well as those with missing clinical pathological or follow-up information

In this international, retrospective cohort study, the cohort of Chinese enrolled patients who underwent curative surgery for AA at the National Cancer Center of China, Chinese Academy of Medical Sciences, Cancer Hospital, from January 1, 1998, to December 31, 2020 (NCC cohort). The Ethics Committee of the National Cancer Center of China approved the study. Informed consent was secured from participants, authorizing the utilization for potential research. Additionally, patients with AA between January 1, 2004, and December 31, 2017, in the surveillance, epidemiology and end results program were collected as the Western cohort. In which, 12 registries were enrolled including Alaska Natives, California, Connecticut, Georgia, Hawaii, Iowa, Kentucky, Louisiana, New Jersey, New Mexico, Seattle (Puget Sound), and Utah.