The goal of this observational study is to determine how often lymph node metastases occur in the splenic hilum and surrounding fat in patients with left-sided pancreatic cancer.

The main question the study aims to answer is:

Is spleen removal necessary in all cases, or is the risk of lymph node metastases in the fat around the spleen low enough to reconsider this standard practice?

Currently, spleen removal is part of the standard treatment for patients with left-sided pancreatic cancer to ensure that any potential lymph node metastases in the surrounding fat are also removed. However, the likelihood of metastases in this area is low, and spleen removal carries risks.

This study is a first step toward changing the treatment approach. If the findings show that metastases in the fat around the spleen are rare, the next step will be a randomized trial to further investigate whether spleen removal is necessary.

Splenectomy is routinely performed during surgical resection of left-sided pancreatic ductal adenocarcinoma (PDAC) with the primary aim to facilitate adequate lymphadenectomy. However, asplenia is associated with several risks, including overwhelming post-splenectomy sepsis, and an increased risk of the development of cancer. Until several years ago, splenectomy was also routine practice in the surgical treatment of gastric cancer. Recently, several studies have shown that spleen-preservation in patients with gastric cancer is safe and therefore current guidelines advise against splenectomy. The rate of involved lymph nodes (LNs) in the splenic hilum (LN station 10) described in literature differs from 0 to 10% of patients. In these studies, the definition of the splenic hilum is often unclear and therefore these outcomes are difficult to interpret. Spleen-preservation in left-sided pancreatectomy for PDAC is currently not common practice in The Netherlands and goes against treatment guidelines. Two retrospective studies have suggested that spleenpreservation did not impair oncological outcomes and that postoperative complications occurred less after spleen preservation. However, these studies were retrospective, single-center and only included a very small number of patients and are therefore not providing enough evidence to change current practice. The SPLENDID-project focuses on evaluating the oncological safety of spleen-preservation in patients with left-sided PDAC. A prospective cohort study will be performed including all patients who undergo a left-sided pancreatectomy with splenectomy. The specimens will be transected at the precise level were spleen preservation (with resection of splenic vessels) would be performed (after removal of the specimen). Ratio of LN involvement will be collected for both specimen parts. Additionally, oncological patient outcomes, including survival, will be collected. When the pathological assessment confirms a <9% LN involvement rate in the perihilar space, the next step will be to assess spleen preservation in an international, multicenter randomized controlled trial.

Inclusion Criteria:

• All consecutive adult patients (≥ 18 years) who undergo an open or minimally invasive (i.e., robot-assisted or laparoscopic) left-sided pancreatectomy with concomitant splenectomy for primary resectable, borderline resectable, and locally advanced left-sided PDAC

Exclusion Criteria:

• Tumor involvement or abutment of the spleen

Patients from hospitals performing pancreatic surgery