The relationship between the prognostic nutritional index and lymphovascular and perineural invasion of the tumor in patients diagnosed with gastric cancer and its effect on overall survival

Aim: Gastric cancer (GC) is usually diagnosed at an advanced stage with poor prognosis, and lymph node metastasis is a key factor negatively affecting prognosis and determining the clinical management of GC. The Prognostic Nutritional Index (PNI) has been used as a prognostic indicator for GC. A low PNI value has been identified as a predictor of poor prognosis for lymphovascular invasion(LVI) and perineural invasion(PeNI) in many malignancies. In this thesis, we hypothesized that PNI is associated with LVI/PeNI and survival outcomes in patients with GC, and we aimed to evaluate the relationship, prognostic significance, and impact on overall survival of PNI with LVI/PeNI in patients with GC undergoing curative gastrectomy. Materials and Methods: In our study, we retrospectively analyzed the patients who underwent gastric cancer surgery between August 2016-February 2023 in Istanbul University-Cerrahpaşa Cerrahpaşa Medical Faculty. Patients aged 18 and over, diagnosed with gastric adenocarcinoma, with T1-T4, N0-N3 gastric cancer, who did not receive neoadjuvant treatment nor had distant organ metastasis and/nor peritoneal cytology, did not have a second primary cancer diagnosis, had at least 16 lymph nodes excised in pathology results, and underwent elective surgical operation were included. PNI calculation was performed using the formula 10 × serum albumin concentration (g/dL) + 0.005 × lymphocyte count (number/mm3). In the study, a cutoff value of 39.8 was taken for the prognostic nutritional index (PNI), and PNI<39.8 was defined as moderate to severe malnutrition. Patients were grouped into PNI-low group (PNI<39.8) and the PNI-high group (PNI≥39.8). Results: The study included 270 patients aged 23 to 90 years. The mean age was 61.45±12.27 years, with 186 cases (68.89%) male and 84 (31.11%) female. The mean PNI was calculated as 39.8±6.35. Perineural invasion was positive in 232 cases (85.93%), and LVI in 248 cases (91.85%). The mean tumor diameter was 6.84±4.39 cm, and the mean regional lymph node count was 28.40±11.83. Regional lymph node involvement was present in 188 cases (74.44%). Regarding invasion depth, T1 tumor was found in 33 cases (12.22%), T2 in 17 cases (6.30%), T3 in 41 cases (15.19%), and T4 in 179 cases (66.30%). When evaluated as N status, N0 was found in 69 cases (25.56%), N1 in 32 cases (11.85%), N2 in 52 cases (19.26%), and N3 in 117 cases (43.33%). It was observed that in patients with PNI<39.8, the PNI value was lower in deceased patients compared to survivors, and in patients with PNI>39.8, those without perineural invasion had a better survival. The presence of perineural invasion in patients with PNI>39.8 increased the mortality risk by 2.088 units, while in patients with PNI>39.8, better survival was observed in those without LVI. The presence of LVI increased the mortality risk by 3.171 units in patients with PNI>39.8. Mortality developed in 166 cases (61.48%) during the five-year follow-up period. The five-year overall survival rate was 31.02±21.73 months. Conclusion: In patients with gastric cancer, PNI, LVI, and PeNI are independent prognostic factors for overall survival in postoperative patients. While low PNI score is a poor prognostic factor on its own, positive LVI and PeNI involvement in cases with high PNI scores negatively affect survival. We found that perineural invasion and lymphovascular invasion rates are higher in patients with low PNI compared to those with high PNI, and this has an impact on mortality.