Peritoneal surface malignancies are difficult to detect due to their non-specific presentation. Thus, clinicians should maintain a low threshold for considering its presence, even at the diagnosis of a primary tumour. GPs are key to improving outcomes though timely referral to specialist centres – where a multidisciplinary team approach can personalise and optimise treatment intervention.

INTRODUCTION

Peritoneal surface malignancies (PSM) represent a wide variety of cancers with peritoneal involvement.

The tumours may arise from the peritoneum (such as malignant peritoneal mesothelioma and primary peritoneal cancer) or more commonly from the spread to the peritoneum from primary tumours of other organs. These include intra-abdominal (gastrointestinal including appendix, reproductive and genitourinary tracts) and extra-abdominal (breast, lung and skin) origins.

Incidence of PSM

PSM can be detected at the diagnosis of a primary tumour (synchronous PSM) or develop months to years after primary tumour resection (metachronous PSM).

The incidence of PSM varies according to the underlying primary tumour, with the highest incidence noted in patients with the following:

• Ovarian cancer (61-75%)
• Gastric cancer (5-20% synchronous and up to 40% metachronous PSM)
• Colorectal cancer (5-10% synchronous and 15-30% metachronous PSM)

However, the true incidence of PSM is likely underestimated due to challenges in radiological detection and the lack of specialty-specific training.^1-4 　

Figure 1 Peritoneal surface malignancies (click to expand infographic)

CLINICAL PRESENTATION OF PSM

The presentation of PSM is typically associated with specific organ involvement, which includes:

• Abdominal pain
• Mass
• Distension
• Nausea
• Vomiting
• Change in bowel habits
• Rectal or vaginal bleeding
• Unexplained loss of weight
• Loss of appetite

However, given the non-specific clinical presentation, clinicians should maintain a low threshold for considering the presence of PSM, even at the diagnosis of a primary tumour.

It is therefore imperative to provide early referral to a specialised centre such as the Department of Sarcoma, Peritoneal and Rare Tumours (SPRinT) at the National Cancer Centre Singapore (NCCS) for the evaluation of disease extent for optimal treatment intervention.

CURRENT TREATMENT MODALITIES FOR PSM

Historically, PSM was considered a terminal disease with dismal prognosis accompanied by a poor quality of life (QoL) due to limited therapeutic options.

In the past few decades, refinement in patient selection and the introduction of new clinical modalities such as cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (HIPEC) have dramatically changed the landscapes and prognoses in PSM.^5,6

1. Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC)

CRS is the principal component of curative treatment for PSM and involves complex surgical procedures to remove all visible tumour implants within the abdomen. Following CRS, a high concentration of heated chemotherapy is instilled intra-abdominally to eradicate residual microscopic tumour cells.

Patient outcomes and safety

Treatment with CRS and HIPEC in selected patients has been shown to prolong survival, with a median survival of 73 months in ovarian cancer and 22-47 months in colorectal cancer.^7-8

Furthermore, CRS and HIPEC procedures performed in high-volume centres are considered safe, with morbidity and mortality rates equivalent to other major oncologic surgical procedures.⁹

In terms of QoL, patients will typically undergo a transient deterioration of QoL within the first three months before returning to baseline or see an improvement by six to 12 months.^10,11

Patient selection

The criteria for the selection of candidates for CRS and HIPEC procedures are as follows:

• Disease is limited to the abdominal cavity based on radiological evaluation
• The ability to achieve no or minimal residual disease
• The patient’s fitness is suitable to undergo CRS and HIPEC safely (Eastern Cooperative Oncology Group performance status 0 or 1)

Figure 2 Schematic of CRS and HIPEC procedure

Despite the evidence for CRS and HIPEC, only a minority of patients are eligible for this treatment. At SPRinT, approximately 33% of patients who are considered for CRS and HIPEC complete the procedure.¹²

In patients who are not suitable to undergo CRS and HIPEC, palliative surgery, systemic or intraperitoneal chemotherapy can be performed to relieve symptoms.

2. Neoadjuvant bidirectional chemotherapy

Newer forms of chemotherapy administration such as neoadjuvant bidirectional chemotherapy have also been developed in attempt to downstage disease and improve the likelihood of complete CRS.

This treatment modality uses multiple and repeated intraperitoneal and systemic chemotherapy to target PSM from both sides of the peritoneum (the peritoneal cavity and subperitoneal blood vessels).

Patient outcomes

Using this treatment in gastric PSM, the rate of complete CRS was increased and overall survival was improved (median survival of 15.1 months).¹³

3. Pressurised intraperitoneal aerosolised chemotherapy (PIPAC)

Pressurised intraperitoneal aerosolised chemotherapy (PIPAC) is a novel treatment modality that was recently adopted as a form of palliative treatment for PSM. It uses a minimally invasive keyhole procedure to administer chemotherapy directly into the abdominal cavity in an aerosol form.

Patient outcomes

This procedure has been shown to be safe with minimal side effects and improved QoL. Treatment response was also reported in 62-88% of ovarian cancer cases (median survival of 11-14.1 months), 50-91% for gastric cancer (median survival of 8.4-15.4 months), and 71-86% of colorectal cancer cases (median survival of 15.7 months).¹⁴

Figure 3 Schematic of PIPAC setup 　

THE COMPREHENSIVE PERITONEAL DISEASE PROGRAMME AT NCCS

The diagnosis and treatment of PSM pose an interdisciplinary challenge that requires a dedicated multidisciplinary team approach with expertise in performing complex oncological procedures for the best possible outcome.

At NCCS, all cases are reviewed by a multidisciplinary team with extensive experience in the management of PSM, which comprises surgical oncologists, medical oncologists, radiologists, pathologists, a multidisciplinary palliative intervention team and a research team. This allows for personalised medical treatment for each patient.

With a team with wide-ranging expertise, the patient has access to a comprehensive array of up-to-date medical treatments for PSM. SPRinT surgeons have much experience performing CRS and HIPEC in Asia, with over 500 procedures since 2001 and with outcomes comparable to other international high-volume centres.¹⁵

THE SPRinT SERIES: PARTNERING GPs TO CARE FOR ADVANCED AND RARE CANCERS

This is the third in a five-part series of articles, ‘The SPRinT Series’ – in which we discuss the work that SPRinT does, the key aspects of SPRinT’s clinical focus and the role of general practitioners (GPs) in providing care.

Due to the rarity of these tumours, it is critical for patients to be promptly referred to a specialist department/centre, such as SPRinT, to provide the best outcomes.

GPs are our first line of defence, and close collaboration between SPRinT and the GP community is essential for the timely diagnosis and referral of patients with rare tumours.

Read the other parts of the series here:

• Part 1: Partnering GPs to Care for Advanced and Rare Cancers
• Part 2: Improving Sarcoma Outcomes with Early Detection
  
  

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