A composition for use in the treatment of a pancreatic tumour or cyst comprising microspheres which comprise a water insoluble, water-swellable polymer and a chemotherapeutic agent； wherein the microspheres, when equilibrated in water at 37°C, comprise at least 40 wt% water based on weight of polymer plus water, wherein the polymer is anionically charged at pH7 and the chemotherapeutic agent is cationically charged and electrostatically associated with the polymer, and wherein the composition further comprises a viscosity modifier.
