Clinical evaluation of tumor-stroma ratio in pseudomyxoma peritonei from the appendix

Abstract

To evaluate the effect of tumor-stroma ratio (TSR) on disease progression and prognosis of pseudomyxoma peritonei (PMP) from the appendix. The study included 30 PMP patients with complete individual patient data, who underwent cytoreductive surgery (CRS) plus hyperthermic intraperitoneal chemotherapy (HIPEC) in Beijing Shijitan Hospital. Image-Pro Plus was used to quantitatively analyze the proportion of tumor and stromal areas in hematoxylin-eosin staining pathological images, from which TSR was derived. Correlation studies were conducted to evaluate the relationships between TSR and clinicopathological features, immunohistochemical characteristics, and prognosis of PMP. Among 30 PMP patients, there were 16 males (53.3%) and 14 females (46.7%), with the mean age of (54.9±2.3) years. There were 15 cases (50.0%) of low-grade mucinous carcinoma peritonei (LMCP) and high-grade mucinous carcinoma peritonei (HMCP), respectively, with vascular tumor emboli occurring in 4 cases (13.3%), nerve invasion occurring in 3 cases (10.0%), and lymphatic metastasis occurring in 4 cases (13.3%). The median peritoneal cancer index (PCI) score was 36 (range: 3-39). The median TSR was 8% (range: 2%-24%), with TSR≤10% in 19 cases (63.3%) and TSR>10% in 11 cases (36.7%). Immunohistochemistry showed that 16 cases (53.3%) had Ki67 label index ≤ 50% and 14 cases (46.7%) > 50%. The mutation rate of p53 was 56.7% and the loss rate of MMR protein was 11.8%. In addition, the expression rates of MUC2, MUC5AC, CDX2, CK7, and CK20 were 66.7%, 100.0%, 82.6%, 56.0%, and 92.3%, respectively. There were significant correlations between TSR and histopathological types, nerve invasion, Ki67 label index, and p53 mutation (P<0.05 for all). At the end of the last follow-up, 21 patients (70.0%) died and 9 patients (30.0%) survived, including 6 patients survived with tumor. The median overall survival (OS) was 12.7 months (95%CI: 10.4-11.5 months), and the 1-, 2-, and 3-year survival rates were 60.5%, 32.3%, and 27.7%, respectively. The median OS was 19.4 months (95%CI: 3.0-35.9 months) in the TSR≤10% group, versus 12.6 months (95%CI: 0.7-24.5 months) in the TSR>10% group (χ2=3.996, P=0.046). TSR is correlated with histopathological types, tumor proliferation, invasion behaviors and prognosis of PMP, thus could be a new prognostic indicator for PMP.