Objective Although postoperative adjuvant chemotherapy is generally recommended for early-stage ovarian cancer, it remains unclear whether adjuvant chemotherapy is also effective for clear cell carcinoma (CCC).

Methods Seventy-three patients with stage I CCC of the ovary who had undergone complete surgical staging formed the study population (stage IA, 20 patients; stage IC, 53 patients). Survival and multivariate analyses were retrospectively performed to determine the effectiveness of postoperative chemotherapy in these patients.

Results Of the total (73 patients), 30 patients received adjuvant chemotherapy (stage I C-positive), whereas 43 patients did not (stage I C-negative). The 5-year progression-free survival (PFS) and 5-year overall survival (OS) rates for the stage I C-positive group were 80.1% and 87.4% compared with 73.9% and 81.7% for the stage I C-negative group. The differences in survival between these groups were not significant (PFS: P = 0.610; OS: P = 0.557). Four of the patients with stage IA CCC underwent chemotherapy, whereas the remaining 16 patients received no additional therapy. No recurrence was observed in either group. Of the patients with stage IC CCC, 26 patients underwent chemotherapy (stage IC C-positive) and 27 received no additional therapy (stage IC C-negative). There was no statistical difference in PFS and OS between the stage IC C-positive and stage IC C-negative groups. Of the patients with stage IC without artificial rupture, the 5-year PFS rates of the C-positive and C-negative patients were 69.6% and 34.6%, respectively, but the 5-year OS rates were 75.0% and 70.0%, respectively (not significant). Multivariate analyses confirmed that the presence or absence of adjuvant chemotherapy was not a prognostic indicator.

Conclusions The current study was performed only in fully staged patients, suggesting that postoperative adjuvant chemotherapy is not necessary for stage IA CCC patients. For patients with stage IC CCC patients, adjuvant chemotherapy suppressed recurrence, but the effectiveness was insufficient in our limited study. Further studies are required to clarify this.