Ovarian cancer is the sixth most common
cancer in women worldwide and is the leading cause of
death among gynecologic malignancies in Western
Europe and North America. In Thailand, ovarian cancer
is the second most common cancer of the female genital
tract after cervical cancer with an annual incidence of
5.6 per 100,000 women, and a death rate of 2.6 per 100,000
women per year(1). Due to the often asymptomatic
nature of the early stage of disease, many cases of
ovarian cancer present in the advanced stage for
which the 5-year survival rate remains low(2). Less than
one-third of patients with ovarian cancers have been
diagnosed before the tumor cells have spread(3). It is
beyond an obvious indictment of the authors’ ability
to detect the condition in its earliest stages. Thus, when
suspicious evidence of ovarian mass has been found,
the importance lies in the fact that it could be malignant.
Several attempts have been made to discriminate
these conditions for an appropriate operation at the
time of initial exploration, eliminating the morbidity and
expense of a second procedure. Clinicians have a wide
range of investigations that are helpful in the diagnosis
of ovarian cancer such as pelvic examination, ultrasonography,
and tumor markers levels. One of the most
distinguished and reliable tumor markers is Carbohydrate
Antigen 125, or CA125.
The estimation of clinical value of CA125 in
pre-operative diagnosis and monitoring of ovarian malignancies
has been mentioned. Available data suggests
that CA125 is elevated in the majority of epithelial ovarian
malignancies prior to clinical presentation. Large
screening trials for ovarian cancer indicated the use of
serum CA125 cutoff value at higher than 35 U/mL as
suggesting malignancy(4-9). Therefore, the level of 0-35
U/mL of serum CA125 has been used as normal value
in most service laboratories including the immunology
laboratory, Department of Immunology, Faculty of
Medicine Siriraj Hospital, Mahidol University