An 18 year population-based study on site of origin and outcome of patients with peritoneal malignancy in Ireland

Peritoneal malignancy (PM) is predominantly metastatic spread from advanced gastrointestinal or gynaecological cancer. PM is generally considered incurable and therefore has rarely been the focus of novel therapeutic strategies. 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 during the period 1994-2012. Patient and tumour characteristics were retrieved and survival outcomes calculated. 5791 patients were diagnosed during the study period. Median age at diagnosis was 68 years; females accounted for 62%. The incidence increased annually from 228 in 1994 to 401 in 2012. Primary PM accounted for 3% of cases. Colorectal (22%), ovarian (16%) and gastric (13%) 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, while 44% (n = 2560) had tumour directed chemotherapy. The median survival (MS) in patients with secondary PM was 6.6 months, and did not improve significantly during the study period. Outcomes were best in patients with ovarian cancer (MS 15.9 months) and colorectal cancer (MS 14.3 months) and worst in patients with lung (MS 2.4 months) and pancreas (MS 1.9 months) cancers. This is the first population-based study from Ireland to report the incidence and outcomes for PM. PM is more common than previously reported and survival remains poor. These findings highlight the need for greater clinician awareness and the need to focus on new therapeutic approaches to improve patient outcomes.