COLOSARC-Q is a multicenter study with the objective of providing an up-to-date assessment of colorectal resections and reconstruction techniques in the context of multivisceral resections for retroperitoneal sarcomas, as well as colorectal surgery-associated complications and their impact on patients' quality of life.

In multivisceral resections involving the colon and rectum, the primary aim is to achieve complete resection and preserve organ function. However, multivisceral resections have a high risk of perioperative morbidity including anastomotic leakage. The proposed project aims to determine the number of primary anastomoses, their insufficiency rates, and the fraction of patients with primary and secondary stomas. In addition, the patients' quality of life after multivisceral sarcoma resection is to be recorded using standardized surveys.

The analysis has the potential to facilitate intraoperative decision-making for colorectal resections in the context of multivisceral resections.

The primary goal of retroperitoneal sarcoma surgery is to achieve complete resection. The resection of retroperitoneal sarcomas (RPS) usually involves the removal of parts of the colon. While there is good data on surgical principles and postoperative complications of multivisceral resections in RPS as a whole (1, 2), there is little evidence on the frequency of temporary or permanent stomas and complications associated with intestinal surgery (e.g., number of anastomotic leackages in relation to the number of intestinal anastomoses performed) and their impact on the quality of life of those affected.

The COLOSARC-Q study is a multicenter, non-interventional study with the aim of documenting

• colorectal resection and reconstruction techniques in connection with multivisceral resections in retroperitoneal sarcomas (RPS),
• complications associated with intestinal surgery in multivisceral resections, and
• the resulting effects on the quality of life of sarcoma patients. The project plans to include 120 patients with retroperitoneal sarcomas who have undergone colon resection as part of a multivisceral resection at a DKG-certified sarcoma center or hospital that meets certification-equivalent criteria. For these patients, patient-, tumor-, and treatment-specific parameters (all patients), standardized questionnaires on health-related quality of life (EORTC QLQ - C30 (version 3.0)) and bowel function (EORTC QLQ - CR29) (expected response rate ≥ 50%) and semi-structured interviews with the aim of recording specific problems that may not be covered in the questionnaires (e.g., regarding stoma placement, nutritional status, treatment sequence, or home care; n = 10-15).

COLOSARC-Q has the potential to improve preoperative participatory decision-making and intraoperative strategy in colorectal resections as part of multivisceral resections in order to reduce complication rates and develop surgical strategies tailored to specific patient needs.

Inclusion Criteria:

• Histological confirmation with evidence of a retroperitoneal sarcoma
• Tumor resection with colorectal resection
• Surgery in a DKG-certified sarcoma center or hospital that meets certification-equivalent criteria
• Age 18 years or older
• Written consent

Exclusion Criteria:

• Absence of consent

Patients with primary, retroperitoneal sarcomas who underwent surgery with colorectal resection at DKG-certified sarcoma centers or hospitals in Germany and Switzerland that meet certification-equivalent criteria.