Platelet and Neutrophil Counts as Predictive Markers of Neoadjuvant Therapy Efficacy in Rectal Cancer

To investigate pretreatment platelet and neutrophil counts as well as a combined platelet-neutrophil (PN) index for prognostic information in patients with rectal adenocarcinoma that received neoadjuvant treatment.

Charts from 164 patients with localized rectal adenocarcinoma were retrospectively reviewed, and 112 patients with complete data were included in the study. Patients were stratified in groups according to their neutrophil counts, platelet counts, and a combined platelet/neutrophil (PN) index. Baseline parameters of the groups were compared using the x² test. Pathologic responses on the surgical specimen of patients with lower platelet counts (≤ 350 × 10⁹/L), lower neutrophil counts (≤ 7.5 × 10⁹/L), and a lower PN index were compared with those of patients with higher platelet counts (> 350 × 10⁹/L), higher neutrophil counts (> 7.5 × 10⁹/L), and a higher PN index using the x² test. Kaplan-Meier curves of overall and progression free survival were constructed and compared with the log-rank test.

A total of 33 (29.5%) patients belonged to the high-PN index group, and 79 (70.9%) patients belonged to the low-PN index group. A significant difference was present between the two groups with regard to pathologic response. Patients with both high platelet and high neutrophil counts were less likely to have a complete pathologic response than those in the low-PN index group (P = 0.039). Additionally, tumor location and tumor stage were significantly associated with complete pathologic response to neoadjuvant treatment. Patients with a complete response were more likely to present with a low tumor (≤ 5 cm from the anal verge). Likewise, patients diagnosed with stage II disease were more likely to experience complete response than those diagnosed with stage III (x² test P = 0.016). There was no significant difference in overall and progression free survival between the two platelet groups (log-rank P = 0.73 and 0.40, respectively) and the two PN index groups (log-rank P = 0.92 and 0.43, respectively).

In this retrospective analysis, the combination of higher platelet and neutrophil counts at the time of diagnosis had predictive value with respect to complete pathologic response to neoadjuvant treatment in locally advanced rectal cancer.