Background: Little is known about the natural history of ovarian cancer with respect to the change of serum CA125 level.
Methods: The Shizuoka Cohort Study on Ovarian Cancer Screening (SCSOCS) Trial contains approximately 100,000 data on serum tumor marker CA125 prospectively obtained from more than 70,000 women. We reviewed the clinical charts and collected serum samples 2 months to 9.4 years prior to the surgery were available.
Results: In 396 (95%) of the 419 patients with ovarian cancer, one serum sample was present before the diagnosis (mean, 4.1 years). The change of CA125 level before the diagnosis of ovarian cancer could be clearly separated into two groups according to the length of the following intervals: 47% (107/228) of patients with non-serous-type ovarian cancers develop secondarily from slightly elevated CA125 level (35 <CA125 <65 U/ml), with a mean interval of 3.8 years. On the other hand, 75% (126/168) of patients with serous-type ovarian cancer seem to develop suddenly from a normal CA125 level (CA125 <35 U/ml), with a mean interval of 1.4 years (p=0.011).
Conclusions: The slightly elevated CA125 level is typically present many years before the diagnosis especially in patients with non-serous-type ovarian cancer. However, serous-type ovarian cancer may exhibit a rapid progression possibly through de novo carcinogenesis.