TAC1 and neoplasm: In addition, tumour markers can have prognostic value: plasma neurokinin-A has been shown to be an accurate marker of prognosis in midgut NETs, with rising neurokinin-A levels despite somatostatin analogue therapy shown to be associated with poorer prognosis (Turner et al, 2006); patients with CgA greater than 5000 μg l−1 have a 5-year survival of only 22% as opposed to 63% for patients with serum chromogranin-A levels of less than 5000 μg l−1 (Janson et al, 1997).