When bowel cancer spreads to the peritoneum, which is the thin layer of tissue lining the inside of the abdomen and covering stomach, liver or bowel, it is known as a peritoneal metastasis. Bowel cancer tumours can form on the peritoneum or the surface of the organs that it covers.
When bowel cancer has spread to the peritoneum, then it is considered advanced, stage IV cancer.
Cancer that develops from the peritoneum itself, known as primary peritoneal cancer, is very rare.
The symptoms of peritoneal metastasis include the following:
- Ascites – this is a build-up of fluid in the abdomen, causing swelling and bloating, and is very common for patients with peritoneal metastases
- Obstructions – peritoneal metastases can cause blockages of the bowel
- Abdominal pain
- Nausea and vomiting
- Weight loss
Patients that are suffering from cancer of the ovaries, bowel, colon, rectum, stomach and pancreas are at risk of developing peritoneal metastases.
Treatment for peritoneal metastasis could include chemotherapy and surgery.
Chemotherapy can be used to shrink the cancer and can be used in conjunction with biological therapies, such as Cetuximab (Erbitux), Panitumumab (Vectibix), or bevacizumab (Avastin) . A biomarker test may be performed to see whether you will benefit from one of these targeted therapies.
Peritoneal surgery is performed to remove visible tumours from the peritoneum, which is known as cytoreductive surgery. You may also need parts of some organs removed if they are affected.
Cytoreductive surgery may be combined with Hyperthermic lntraperitoneal Chemotherapy (HIPEC), a process whereby a heated chemotherapy solution is applied in the peritoneal cavity.
A potential new treatment is called PIPAC which stands for pressurised intraperitoneal aerosolised chemotherapy and is currently in clinical trials. It is chemotherapy that is delivered directly into the abdomen during a short general anaesthetic and aims to shrink tumours in the peritoneum.
Diagnosis can be challenging. Ascitic fluid may be drained and assessed, or CT or MRI scans may be ordered and reviewed by expert radiology doctors. Keyhole surgery may also be performed to look inside the abdomen.