Peritoneal dissemination describes a condition where cancer cells spread to the peritoneum, a thin membrane lining the abdominal cavity and covering most abdominal organs. This leads to new tumor growths on these surfaces.
Understanding Peritoneal Dissemination
The peritoneum is a continuous, serous membrane that forms a protective sac within the abdomen. It consists of two main layers: the parietal peritoneum, which lines the abdominal wall, and the visceral peritoneum, which covers organs like the stomach, intestines, and liver. This membrane produces a small amount of fluid, allowing organs to move smoothly against each other.
Cancer cells primarily spread to the peritoneum through direct extension or by shedding into the peritoneal fluid. In direct extension, a tumor from an organ like the colon or ovary grows through its wall and directly invades the adjacent peritoneal surface. Cells can also detach from a primary tumor and float freely within the peritoneal fluid, eventually implanting on distant parts of the peritoneum. This mechanism is often observed in ovarian cancer.
Less commonly, cancer cells can reach the peritoneum through lymphatic or hematogenous routes, meaning they travel through the body’s lymphatic system or bloodstream. Once these cells implant, they can proliferate and form new tumor nodules across the peritoneal surface. This spread differs from distant metastasis, which refers to cancer spreading to organs far from the primary site, such as the lungs or bones.
Several primary cancers frequently lead to peritoneal dissemination. Ovarian cancer is a common culprit, often spreading early to the peritoneum. Colorectal, gastric (stomach), and appendiceal cancers also have a notable propensity to spread this way. Pancreatic and gallbladder cancers can also result in peritoneal involvement.
Identifying Peritoneal Dissemination
Recognizing peritoneal dissemination often begins with a patient experiencing various non-specific symptoms. Common indicators include persistent abdominal pain or discomfort, a noticeable increase in abdominal girth due to bloating, and the accumulation of fluid in the abdomen, a condition known as ascites. Patients may also report changes in bowel habits, such as constipation or diarrhea, or a general feeling of fullness even after eating small amounts of food.
Diagnostic imaging techniques are used to identify peritoneal dissemination. Computed tomography (CT) scans are often the initial imaging, providing cross-sectional images that reveal signs like ascites or thickened peritoneal surfaces. Magnetic resonance imaging (MRI) offers greater soft tissue contrast and can sometimes detect smaller tumor implants than a CT scan. Positron emission tomography (PET) scans can help identify metabolically active tumor cells, but may not always detect very small or diffuse implants.
To confirm diagnosis and assess disease extent, a diagnostic laparoscopy is often performed. This minimally invasive surgical procedure involves inserting a thin, lighted tube with a camera into the abdomen to visualize peritoneal surfaces directly. During laparoscopy, biopsies of suspicious areas are taken for pathological examination, providing definitive confirmation of cancer cell presence. Biopsy results are crucial for determining cancer type and guiding treatment decisions.
Blood tests for tumor markers, such as CA-125 for ovarian cancer or CEA for colorectal cancer, may be elevated in patients with peritoneal dissemination. While these markers support cancer suspicion and monitor treatment response, they are not definitive diagnostic tools. Levels can be influenced by non-cancerous conditions; diagnosis relies on clinical symptoms, imaging, and pathological confirmation from biopsies.
Treatment Approaches
Treating peritoneal dissemination often involves a comprehensive, multi-disciplinary approach to remove visible tumors and control microscopic disease. Cytoreductive surgery (CRS) is a primary treatment for eligible patients, removing as much cancerous tissue as possible from the peritoneum and affected organs. The goal of CRS is to achieve “complete cytoreduction,” meaning no visible tumor nodules larger than 2.5 millimeters remain after surgery.
Following CRS, hyperthermic intraperitoneal chemotherapy (HIPEC) is administered. This procedure involves circulating a heated chemotherapy solution directly into the abdominal cavity for a short period, for 60 to 120 minutes, immediately after tumor removal. Heat enhances chemotherapy penetration into remaining microscopic cancer cells and has a direct cytotoxic effect. Localized delivery allows higher chemotherapy concentrations to reach abdominal cancer cells, limiting systemic side effects.
Another approach, early postoperative intraperitoneal chemotherapy (EPIC), involves administering chemotherapy drugs into the abdominal cavity through catheters placed during surgery. This is done over several days following CRS, without the heating component. EPIC aims to target any residual cancer cells that may remain after surgery and HIPEC, providing a sustained local chemotherapy effect. The choice between HIPEC and EPIC, or their combination, depends on various factors, including the type of cancer and the extent of disease.
Systemic chemotherapy, delivered intravenously, remains a component of treatment for many patients with peritoneal dissemination. These drugs travel through the bloodstream to target cancer cells throughout the body, including those that may have spread beyond the peritoneum. Systemic chemotherapy can be used before CRS (neoadjuvant), after CRS and HIPEC (adjuvant), or as a primary treatment for patients not eligible for surgery.
Targeted therapies and immunotherapies are also being explored and used, offering more personalized treatment options. Targeted therapies block specific pathways or proteins involved in cancer growth, while immunotherapies boost the body’s own immune system to fight cancer cells. The management of peritoneal dissemination typically requires collaboration among surgical oncologists, medical oncologists, radiation oncologists, and other specialists to develop an individualized treatment plan for each patient.