CA19-9 decrease and survival according to platelet level in patients with advanced pancreatic cancer

CA19-9 decrease during treatment has been associated with superior survival of pancreatic cancer in several studies. The evidence to show the correlation of high platelet level with inferior survival is insufficient in pancreatic cancer. It also remains unclear whether the association between CA19-9 decrease and survival was corresponded to different levels of platelet in metastatic pancreatic cancer.

We measured CA19-9 serum concentration and platelet level at baseline and after the second cycle of chemotherapy for 200 advanced pancreatic cancer patients. A Cox proportional hazards model was used to compute mortality hazard ratios (HRs) for CA19-9 decrease, adjusting for potential confounders, including age, sex, KPS, prediagnosis body mass index, Diabetes Mellitus, tumor location, first-line chemotherapy regimen, and radiotherapy.

We found that the association of CA19-9 decrease with superior overall survival was stronger in advanced pancreatic cancer with a low level of platelet (P_interaction <  0.001) compared with intermediate and high level of platelet. Multivariable-adjusted hazard ratios per unit decrease of CA19-9 change was 0.45 [95% confidence interval (CI), 0.33 to 0.62] in cases with low platelet level, 0.74 (95% CI, 0.50 to 1.09) in cases with intermediate platelet level, and 0.94 (95% CI, 0.74 to 1.10) in cases with high platelet level. A similar differential association was found between CA19-9 decrease and progression-free survival in strata of platelet level (P_interaction = 0.034).

The association of CA19-9 decrease with superior pancreatic cancer survival appeared to be pronounced in patients with a low platelet level. This finding could provide supports for the underlying mechanisms of CA19-9 involved in platelet / tumor cell interaction.