Significance of neoadjuvant chemoradiotherapy for borderline resectable pancreatic head cancer: Pathological local invasion and microvessel invasion analysis.

Borderline resectable pancreatic head cancer (BR-PHC) has low resectability due to vascular invasion. Although the clinical effects of neoadjuvant chemoradiotherapy (NAC-RT) for BR-PHC have been examined, few studies have reported its pathological aspects. The present study retrospectively investigated the effect of NAC-RT on the histological features of BR-PHC. A total of 29 patients with BR-PHC who underwent NAC-RT, and 55 controls with resectable PHC, who underwent pancreaticoduodenectomy at the Kurume University Hospital. Tumor staging, lymphovascular invasion (LVI), and microvessel invasion (MVI) were evaluated. The median tumor size in the NAC-RT group was 2.0 cm, and it was smaller than that of the control group (P=0.006). The rates of lymph node metastasis, LVI, and MVI were significantly lower in the NAC-RT group (P<0.001, 0.002, and 0.015, respectively). Overall survival in the NAC-RT group was comparable to that in the control group, although patients with BR-PHC generally had a poorer prognosis than those with resectable PHC. Patients in the NAC-RT group without portal vein invasion (PVI) had a significantly better prognosis than those with PVI in the control group (P=0.002). NAC-RT may be beneficial for patients with BR-PHC by inhibiting local invasion and metastasis as prognosis following resection could be equivalent to that of patients with conventional ductal adenocarcinoma.