Whether you’re a patient or a patient’s loved one, navigating a cancer diagnosis and subsequent treatment can feel very scary sometimes – particularly if it is a rare type of cancer like primary peritoneal cancer. In this article, we break down what primary peritoneal cancer is, how it is diagnosed and what the treatment options are. 

What is primary peritoneal cancer? 

Primary peritoneal cancer, or PPC, is a rare cancer that starts in the lining of the peritoneum.¹

What is the peritoneum?

The peritoneum is the inner lining of the abdomen. It protects your organs and allows nerves and blood vessels to pass through it. Consisting of two layers, the peritoneum has fluid between these layers which prevents friction between them and your organs.²

Symptoms of primary peritoneal cancer

Common symptoms of primary peritoneal cancer include: 

• Swollen (distended) abdomen
• Abdominal pain
• Feeling full 
• Sickness
• Constipation
• Tiredness
• Shortness of breath
• Losing weight 
• Needing to urinate more frequently than normal 

Who does primary peritoneal cancer affect? 

Whilst it is possible for men to get primary peritoneal cancer, this is rare. It mainly affects women, with the majority of diagnoses being made in patients over 60 years old (Cancer Research UK).

What causes primary peritoneal cancer?

The exact cause of primary peritoneal cancer is unknown, however research suggests that it may be related to certain gene mutations (such as mutations in BRCA2 or BCOR genes).² 

Diagnosing primary peritoneal cancer

A primary peritoneal carcinoma is a relatively rare tumour, and can be hard to diagnose as it often looks similar to an ovarian tumour (cancer in the ovaries). It is also made difficult by the fact that the symptoms are nonspecific. 

Unfortunately, this means that many people receive a diagnosis when their cancer is already at an advanced stage.³ A diagnosis can usually not be made based on symptoms alone, and require further tests to confirm it.

If you experience the symptoms listed previously, you should contact your GP so that they can carry out the appropriate tests. 

Pelvic examination 

To begin with, your GP may perform a pelvic examination to assess if there is anything out of the ordinary in the pelvic area, such as swelling. They will use 1 or 2 fingers to feel around the inside of your vagina, and may press down on your abdomen (Macmillan Cancer Support). Whilst you may feel a little discomfort, this shouldn’t hurt.

Transabdominal ultrasound scan

In addition to a pelvic examination, if you are experiencing symptoms such as a bloated abdomen, your GP may refer you for an transabdominal ultrasound scan. This is a non-invasive scan which will be performed by an expert and should also not cause any pain.⁴ It will create a picture of the inside of your abdomen using sound waves, as a probe is passed over your abdomen, checking for anything out of the ordinary that could suggest cancer. 

Transvaginal ultrasound scan

You may also be referred for a transvaginal ultrasound scan. This works the same way as an abdominal ultrasound scan, but in this case a probe will be inserted into your vagina to obtain a picture. A combination of both a transabdominal and transvaginal ultrasound can be the most effective way to progress the diagnosis.⁵ If anything abnormal such as a lump or fluid is found, your GP will refer you to a specialist in gynaecological cancer.

CA-125 blood test

Whilst a description of symptoms and ultrasound scans can help healthcare professionals form an initial diagnosis, further studies may be required to test for any tumour markers. Anything in or produced by cancer cells in the body (usually proteins) is considered a tumour marker, and the most effective one for diagnosing primary peritoneal cancer is the CA-125 cancer antigen.⁶

Higher levels of this in the blood may be a sign of primary peritoneal cancer, therefore it is likely that your GP will refer you for a blood test to check for this. 

Abdominal fluid

Sometimes primary peritoneal cancer can cause fluid to build up in the abdomen, and this is called ascites. It is possible that your doctor may take a sample of this fluid using a small needle (after anesthetising the area) to send off for testing. 

Biopsy

As with other cancers, a biopsy can be taken to examine a sample of the affected tissue under a microscope. This microscopic examination is called histopathology and is one of the main ways of confirming a detailed diagnosis of the cancer and its variant (type).⁶

CT scan 

In some cases, a CT scan may be performed to check if the cancer has spread throughout the abdomen.

Treating primary peritoneal cancer

In order to treat primary peritoneal cancer, doctors must first establish what stage it is at – this is called staging the cancer. 

Staging the cancer

Recent research has greatly advanced our understanding of cancers like primary peritoneal cancer, and stages have been revised to reflect how severe the cancer is and how far it has spread throughout the body. 

Doctors use the FIGO staging system for this, which includes 4 stages. Primary peritoneal cancer is never at the earliest stage i.e. stage 1.⁷ It is staged in a similar way to ovarian cancer, but PPC is always at stage 3 or stage 4, meaning it is advanced. In stage 3, the cancer is in the peritoneum and has possibly spread to the lymph nodes in the abdomen. In stage 4, it has spread to organs which are further away in the body, such as the lungs (Cancer Research UK).

For PPC (stage 3 and 4 cancer), the treatment consists of cytoreductive surgery and platinum-based chemotherapy.⁶

Cytoreductive surgery

Cytoreductive surgery, sometimes also referred to as ‘debulking surgery’, will often be performed in order to try to reduce the amount of primary peritoneal cancer cells in the abdomen. The primary goal of the surgery is to remove all visible tumours.⁸ 

As part of the surgery to treat PPC, the specialist may also remove the ovaries and fallopian tubes, the uterus and cervix, and the omentum. Other body parts, such as the intestines, may need to be partially removed if they are affected by tumours (Foundation for Women’s Cancer).

Side effects of this surgery can include: 

• Sickness
• High temperature
• Infection
• Fluid in the abdomen
• Blood clots
• Shortness of breath
• Trouble urinating or passing stools

Platinum-based chemotherapy

In the majority of cases, patients with primary peritoneal cancer will follow a platinum-based chemotherapy regimen after surgery – similar to the regimen for ovarian cancer – as it has been proven to improve survival in PPC patients.⁹

Platinum-based chemotherapy uses drugs which are platinum compounds (such as cisplatin), and is usually administered with a drip. The platinum works by damaging the cancer cells’ DNA and stopping them from multiplying (University of Nottingham). 

Depending on the stage and type of cancer, a course of platinum-based chemotherapy usually lasts about 3 weeks. Doctors will give you extra fluids through a drip both before and after treatment, as this type of chemotherapy can affect the kidneys and the fluids can help with this (Macmillan Cancer Support). 

Unfortunately, platinum-based chemotherapy can have some unpleasant side effects which may include: 

• Infection leading to a fever, cough, shortness of breath, etc.
• Bleeding – heavier periods, nose bleeds, gum bleeding 
• Anaemia (low numbers of red blood cells) which can cause fatigue and dizziness 
• Nausea
• Loss of appetite
• Changes in taste 
• Changes to your heartbeat – faster or slower
• Fatigue 
• Tinnitus - a high-pitched sound in your ears 
• Diarrhoea 

Prognosis in primary peritoneal cancer patients

As primary peritoneal cancer is often at an advanced stage when it is diagnosed, prognosis is often poor. However, results from certain studies have shown that long-term survival is possible in some PPC patients. This is much more likely in the event of an early diagnosis. In one study, the median survival of patients was 23.1 months.⁶

Support for primary peritoneal cancer patients

Receiving a cancer diagnosis can be a very worrying time. If you or someone you love is looking for support, there are lots of options out there. Macmillan cancer support offer free services - you can contact them for advice by phone on 0808 808 00 00 (from the UK), by email, or on an online chat. They also have an online community where you can talk to other people in similar situations.

Summary 

• Primary peritoneal cancer (PPC) is cancer of the peritoneum (the inner lining of the abdomen)
• Symptoms can include abdominal pain/swelling, sickness, tiredness, feeling full, constipation, shortness of breath and losing weight
• Diagnosis is usually made using a pelvic examination, ultrasound scans, CT scans and biopsies 
• Cytoreductive surgery may be performed to remove visible cancer cells 
• The ovaries, fallopian tubes, uterus, cervix and omentum may also be removed 
• Platinum-based chemotherapy with drugs like cisplatin is the best treatment following surgery 
• Prognosis is often poor but long-term survival may be possible 
• Support is available from organisations like Macmillan Cancer Support