Clinical and Experimental Studies in Peritoneal Metastases from Gastric Cancer

Abstract: Gastric cancer (GC) is one of leading causes of death in the world, and peritoneal metastases (PM) are a major site of recurrence. PM from GC implies a poor prognosis, with median overall survival (mOS) approximately 3 months and no survival at five years.The aims of this thesis were to explore the incidence and evaluate prognostic factors for mOS of PM from GC in a defined population; to investigate the outcome of a new multimodal treatment; to analyse the treatment costs, and to investigate differences in drug sensitivity between individual patient samples and between various tumours.The incidence of loco-regional advanced GC was 3.8 per 100,000 person-years. Synchronous loco-regional GC in combination with synchronous distant metastasis was a negative prognostic factor while chemotherapy and good performance status, and radiotherapy plus chemotherapy were positive prognostic factors . There were no significant differences in mOS for the group of patients included during the period 2000-2004 versus 2005-2009, and this lack of improvement in mOS during the past decade justifies new treatment approaches.In a Phase II study of patients treated with neoadjuvant systemic chemotherapy followed by cytoreductive surgery + hyperthermic intraperitoneal chemotherapy, mOS was 14.3 months and for patients with macroscopically radical surgery mOS was 19.1 months. The mean overall cost of the loco-regional treatment was $145,700 compared to $59,300 with systemic chemotherapy treatment.In an ex vivo chemo-sensitivity test, it was determined that GC samples were equivalent to colorectal cancer in chemo-sensitivity to standard drugs and targeted drugs, whereas ovarian cancer samples were more sensitive. The individual GC samples varied considerably in sensitivity to increasing concentrations of the drugs, arguing for individualized drug selection. The incidence of loco-regional advanced GC was more common than previously reported and there were no improvements in mOS over the past decade. The mOS for patients with neoadjuvant systemic chemotherapy followed by macroscopically radical cytoreductive surgery + hyperthermic intraperitoneal chemotherapy was better than in recent reports on treatment with systemic chemotherapy. Treatment of advanced GC patients is costly irrespective of treatment modality. The GC samples varied considerably between individuals in terms of sensitivity to increasing concentrations of the drugs and were comparable to colorectal cancer in chemo-sensitivity.