Prognosis of ovarian clear cell cancer compared with other epithelial cancer types: A population-based analysis

Abstract

In order to compare the clinicopathological characteristics and survival outcomes of patients with ovarian clear cell carcinoma (CCC) to other epithelial cancer types, a total of 27,290 patients were analyzed, including 2,424 patients with CCC (8.9%), 3,505 patients with endometrioid cancer (EC) (12.8%), 2,379 patients with mucinous cancer (MC) (8.7%) and 18,982 patients with serous cancer (SC) (69.6%). Patients with EC had the most favorable prognosis and patients with SC had the poorest prognosis among all epithelial ovarian cancers. Among patients with stage I cancer, patients with CCC had a more favorable prognosis compared with patients with SC, especially after 60 months (landmark analysis results, HR=2.079, P=0.001) and had a poorer prognosis compared with patients with MC [restricted mean survival time (RMST) difference, -3.434 months]. Among patients at stages III and IV, patients with CCC had a poorer prognosis compared with patients with SC (RMST difference in stage III, -7.588 months; RMST difference in stage IV, -15.445 months) and had a more favorable prognosis compared with patients with MC (RMST difference in stage III, 10.850 months; RMST difference in stage IV, 8.430 months). The present results suggested that most patients with CCC exhibited, high grade, an early stage, unilateral status and were of a young age. In general, patients with SC presented the poorest prognosis among all patients with epithelial ovarian cancer and no significant survival difference was found between patients with CCC and MC. However, after adjusting for stage using pairwise comparisons, the prognosis of patients with CCC was found to be more favorable compared with the patients with SC and worse compared with patients with MC at stage I; the results at stage III-IV were opposite and the prognosis of patients with CCC was worse compared with the patients with SC and more favorable compared with the patients with MC.

Keywords: clear cell; epithelial cancer; ovarian cancer; prognosis; survival.

Figure 1.

Flow chart of inclusion and exclusion criteria. SC, serous cancer; CCC, clear cell cancer; MC, mucinous; EC, endometrioid cancer; TNM, tumor node metastasis; AJCC, American Joint Committee on Cancer.

Figure 2.

Kaplan-Meier survival curve for OS and DSS. (A) OS of four types of epithelial ovary cancer. (B) DSS of four types of epithelial ovary cancer. SC, serous cancer; CCC, clear cell cancer; MC, mucinous; EC, endometrioid cancer; OS, overall survival; DSS, disease-specific survival. Log-rank test were used to compare the difference among CCC, EC, MC and SC.

Figure 3.

Kaplan-Meier survival curve for OS between CCC and SC. (A-a) OS between CCC and SC at stage I. (A-b) Landmark analysis of OS between CCC and SC at stage I. The landmark point was 60 months and the hazard ratio was 2.079 (95% confidence interval, 1.320–3.273, P=0.010). (B) OS between CCC and SC at stage II. P=0.600. (C-a) OS between CCC and SC for stage III. P<0.001. (C-b) RMST analysis of OS between CCC and SC at stage III. The shaded area (from 0 to 96 months) indicates 7.588 months, which corresponds to the difference in RMST between CCC and SC. (D-a) OS between CCC and SC at stage IV. P<0.001. (D-b) RMST analysis of OS between CCC and SC at stage IV. The shaded area (from 0 to 120 months) indicates 15.445 months, which corresponds to the difference in RMST between CCC and SC. OS, overall survival; CCC, clear cell cancer; SC, serous cancer; RMST, restricted mean survival time.

Figure 4.

Kaplan-Meier OS curves between patients with CCC and MC. (A-a) OS between CCC and MC at stage I. P=0.020. (A-b) RMST analysis of OS between CCC and MC at stage I. The shaded area (from 0 to 120 months) indicates 3.434 months, which corresponds to the difference of RMST between CCC and MC. (B) OS between CCC and MC at stage II. P=0.600. (C-a) OS between CCC and MC at stage III. (C-b) RMST analysis of OS between CCC and MC at stage III. The shaded area (from 0 to 120 months) indicates 10.850 months, which corresponds to the difference in RMST between CCC and MC. (D-a) OS between CCC and MC at stage IV. (D-b) RMST analysis of OS between CCC and MC at stage IV. The shaded area (from 0 to 120 months) indicates 8.430 months, which corresponds to the difference in RMST between CCC and MC. OS, overall survival; CCC, clear cell cancer; MC, mucinous cancer; RMST, restricted mean survival time.