Peritoneal Cancer

Peritoneal cancer is a rare cancer that develops in the peritoneum – a thin, delicate, silk-like membrane that lines the inside wall of the abdomen and covers the abdominal organs, including the uterus, bladder, and rectum. The peritoneum produces a small amount of lubricating fluid that allows the organs to move smoothly against each other.

The most common type of peritoneal cancer is primary peritoneal carcinoma – a cancer that starts in the peritoneum itself, rather than spreading there from elsewhere. It is very similar to the most common type of ovarian cancer (high-grade serous carcinoma) in terms of its appearance, behaviour, and treatment. In fact, primary peritoneal cancer and ovarian cancer are often considered together as epithelial ovarian cancer for treatment purposes.

It is important to note that peritoneal cancer can also occur as a secondary cancer – when cancer from another organ, such as the ovary, fallopian tube, uterus, colon, stomach, or appendix, spreads to the peritoneum.

Causes and Risk Factors

• Age – the risk increases significantly with age, especially after 60.
• Genetic mutations – particularly BRCA1 and BRCA2 gene mutations. Women with these mutations have a significantly higher risk of both ovarian and primary peritoneal cancer, even after the ovaries have been removed.
• Lynch syndrome (hereditary non-polyposis colorectal cancer) – another genetic condition that increases the risk.
• Strong family history of breast, ovarian, or peritoneal cancer.
• Endometriosis – slightly increases the risk.
• Lifetime number of ovulations – women who started menstruation early, had late menopause, or never had children have a slightly higher risk (as with ovarian cancer).

Symptoms

• Abdominal bloating or swelling – often the most common early symptom.
• Pelvic or abdominal pain – a dull ache, pressure, or discomfort.
• Feeling full quickly after eating (early satiety) – or having a loss of appetite.
• Changes in bowel habits – such as constipation, diarrhoea, or feeling like you cannot empty your bowels fully.
• Changes in bladder habits – needing to urinate more frequently or urgently.
• Unexplained weight loss – without trying.
• Fatigue – persistent tiredness.
• Vaginal bleeding – especially after menopause or bleeding between periods (less common than in ovarian cancer, but can occur).

Diagnosis

• Medical history and physical examination – including a pelvic and abdominal examination to feel for masses or fluid (ascites).
• Blood tests – including the CA-125 tumour marker, which is often raised in peritoneal cancer (though it can also be raised in other conditions like endometriosis or fibroids).
• Transvaginal ultrasound – to visualise the ovaries, uterus, and peritoneal lining.
• CT scan or MRI – to look for tumour deposits in the abdomen and pelvis, and to check for spread to other organs.
• Biopsy – this is the gold standard for diagnosis. It involves taking a small sample of peritoneal tissue, often via a needle guided by ultrasound or CT (image-guided biopsy), or during a laparoscopy (keyhole surgery).
• Ascitic fluid aspiration (paracentesis) – if there is fluid in the abdomen, a sample is taken and analysed for cancer cells.

Treatment

Surgery (Cytoreductive Surgery)

The goal is to remove as much of the cancer as possible. This may involve:

• Removing the omentum (a fatty layer covering the abdominal organs, which is often affected).
• Removing visible tumour deposits from the peritoneum.
• Removing the ovaries, fallopian tubes, and uterus (if not already removed).
• Removing parts of other organs if the cancer has spread to them (such as sections of bowel or the spleen).

The success of surgery is measured by how much tumour is left behind – the goal is no visible residual disease (R0 resection), or minimal disease (less than 1cm).

Chemotherapy

• Most women will receive chemotherapy after surgery (adjuvant chemotherapy) or sometimes before surgery (neoadjuvant chemotherapy) if the cancer is very extensive.
• In some specialist centres, a treatment called HIPEC (Hyperthermic Intraperitoneal Chemotherapy) may be offered, where heated chemotherapy is pumped directly into the abdominal cavity during surgery.

Supportive Care (Palliative Care)

• If the cancer is advanced and cannot be cured, treatment focuses on controlling symptoms, including draining ascites, managing pain, and maintaining quality of life.