• For management of patients with appendiceal tumors without peritoneal involvement the emphasis is on the understanding of the histology of appendiceal tumors and management based on that. Specific emphasis on not performing indiscriminate right hemicolectomies for patients with low-grade appendiceal mucinous neoplasms is highlighted.
• For management of patients with appendiceal tumors with peritoneal involvement there is a significant overarching change in the guidelines: the preference for a period of systemic chemotherapy before surgery in cases with high-grade cancer. The consensus strongly recommends evaluating surgical candidates for cytoreduction surgery in low-grade and high-grade peritoneal disease, and notes that systemic chemotherapy is unlikely to benefit low-grade disease. Repeat surgery is recommended for carefully selected patients, demonstrating an overall survival advantage over non-surgical management.
• Management of peritoneal mesothelioma (PeM) includes new recommendations to observe benign variants of mesothelioma such as the well-differentiated papillary and multicystic, unless they are progressive, symptomatic, or diffuse. Malignant PeM management should be based on a multidisciplinary assessment of patient characteristics, disease histology, and the anticipated success of medical and surgical interventions, with a strong emphasis on multimodal therapy for intermediate-risk and some high-risk patients.
• Management of colorectal cancer (CRC) with peritoneal metastases (PM) includes recommendations of early referral to a peritoneal surface malignancy center for all CRC-PM patients. Foremost is the recommendation to include patients with peritoneal metastases in clinical trials. This was echoed by the patient support organizations who recognized the systematic exclusion of such patients from trials. Further the adoption of curative intent cytoreductive surgery with or without intraperitoneal chemotherapy with mitomycin was also strongly recommended by the experts. A novel recommendation for circulating tumor DNA testing in surveillance was also made, albeit recognizing the weak evidence supporting it.
• Best practices for management of gastric cancer (GC) with PM have been updated to recommend a multidisciplinary preoperative assessment and diagnostic laparoscopy for all patients. Also, patients with a high burden of disease or disease progression should be managed without surgery, in favor of systemic therapy or clinical trials, the guidelines suggest. Conversely, the recommendation for patients with stable or responsive disease is regional therapeutic interventions and surgery. These guidelines prompted alignment with the NCCN gastric cancer guidelines where cytoreductive surgery and intraperitoneal chemotherapy are included in the management of patients with peritoneal-only metastases.
• Management of PM from neuroendocrine neoplasms (NENs) guidelines emphasized the importance of histological grade in the management of neuroendocrine tumors with peritoneal disease. Sequencing of multi-modality therapies based on grade suggests surgery for Grade 1 and 2 well-differentiated NENs with PM after managing functional syndromes. For Grade 3, systemic therapy is the primary recommendation for well-differentiated NENs and poorly differentiated neuroendocrine carcinomas (NECs). The guideline discourages hyperthermic intraperitoneal chemotherapy (HIPEC) for these cases due to limited efficacy and significant toxicity.
• Management of Malignant Gastrointestinal Obstruction with PSM should include a multidisciplinary approach, including early palliative care assessments and goals of care evaluation throughout treatment. Management decisions should be based on the location and severity of obstruction and informed decisions for palliative-intent surgical interventions or stents. Studies demonstrated limited benefits for such interventions in patients with multifocal obstructions, poor performance status, and high-grade and/or high-burden PSMs. In these cases, a recommendation for supportive care or upper gastrointestinal decompression tube placement was favored.
Also in the last year, the Peritoneal Surface Malignancies Consortium published on the topic of benchmarks for work effort measurement for physicians participating in therapies for patients with PSM. The authors conducted a national survey of surgeons performing cytoreductive surgery/HIPEC procedures and established standard of benchmarks for these procedures, noting the significant variability and lack of support for surgeons earlier in their experience.