Patterns of peritoneal Malignancy in Ireland. A population based study

Peritoneal malignancy (PM) most commonly occurs as a result of metastatic spread from advanced gastrointestinal cancer. A minority of cancer arise primarily from the peritoneum.  PM carries a poor prognosis, is generally considered incurable and therefore rarely the focus of novel therapeutic strategies. Population-based data on the true incidence is lacking. This study assessed patterns and survival outcomes for patients with PM in Ireland.

The National Cancer Registry Ireland database was interrogated to identify patients diagnosed with PM between 1994-2012. Patient demographics and tumor characteristics were retrieved and survival outcomes calculated.

5791 patients were diagnosed with PM during the study period. The median age at diagnosis was 68 years; females accounted for 62%. The incidence of PM increased annually from 228 in 1994 to 401 in 2012. Primary PM accounted for 3% of cases. Colorectal (22%), gastric (13%) and ovarian (16%) cancers accounted for the majority of cases of secondary PM. Almost 75% of patients had PM at initial presentation. Almost 40% of patients (n=2274) underwent surgical intervention for their malignancy, while 44% (n=2560) received tumour directed chemotherapy. The median survival (MS) was 6.6 months in patients with secondary PM. Outcomes were best in patients with ovarian cancer PM (MS 15.9 months) and colorectal cancer PM (MS 14.3 months) and worst in primary cancers of the lung (MS 2.4 months) and pancreas (MS 1.9 months).

This is the first population-based study to report the incidence and outcomes for PM in Ireland. Reported rates likely underestimate the true incidence, nevertheless PM is more common than previously thought and survival remains poor. These findings highlight the need for greater clinician awareness and the development of new therapeutic approaches to improve patient outcomes.