Cancer Antigen 125
Marcadores tumoraisÚltima revisão: 7 de abril de 2026. Abordagem de fontes: contexto padrão de interpretação laboratorial, material médico de referência e orientações clínicas ou de saúde pública quando relevantes.
O que é Cancer Antigen 125?
Cancer Antigen 125 (CA-125) is a glycoprotein encoded by the MUC16 gene that is expressed on the surface of cells derived from coelomic epithelium, including the mesothelial lining of the peritoneum, pleura, and pericardium, as well as the epithelium of the fallopian tubes, endometrium, and endocervix. CA-125 is shed from cell surfaces into the bloodstream and can be measured via immunoassay. It was first identified in 1981 using monoclonal antibody OC125, which recognized an antigen consistently elevated in the serum of patients with epithelial ovarian cancer.
CA-125 is most widely used as a serum biomarker for monitoring treatment response and detecting recurrence in patients with epithelial ovarian cancer, particularly serous carcinomas. It is not recommended as a standalone screening tool for ovarian cancer in the general population because of its limited sensitivity in early-stage disease and its poor specificity—many benign conditions also elevate CA-125. However, in combination with transvaginal ultrasound, it may have a role in screening high-risk populations. Serial measurements are generally more informative than single values.
Por que isso importa
CA-125 is the most established serum biomarker for epithelial ovarian cancer, used primarily to monitor treatment response and detect disease recurrence. A rising CA-125 after treatment can signal relapse months before imaging findings appear. However, CA-125 has important limitations: it is elevated in only about 80% of advanced ovarian cancers and fewer than 50% of early-stage cases. Many benign gynecological and non-gynecological conditions can raise CA-125, so results must always be interpreted in clinical context. In premenopausal women, benign elevations are particularly common.
Faixas de referência normais
| Grupo | Faixa | Unidade |
|---|---|---|
| Adults (general) | 0–35 | U/mL |
| Premenopausal women | 0–35 | U/mL |
| Postmenopausal women | 0–20 | U/mL |
As faixas de referência podem variar entre laboratórios. Sempre compare seus resultados com as faixas fornecidas pelo seu local de exame.
O que significam níveis altos de CA-125
Causas comuns
- Epithelial ovarian cancer (especially serous carcinoma)
- Endometriosis
- Uterine fibroids
- Pelvic inflammatory disease
- Menstruation and first trimester pregnancy
- Liver cirrhosis and ascites
- Peritoneal, pleural, or pericardial inflammation
- Endometrial, fallopian tube, and primary peritoneal cancers
- Pancreatitis and pancreatic cancer
- Congestive heart failure
Possíveis sintomas
- Abdominal bloating or swelling
- Pelvic or abdominal pain
- Feeling full quickly when eating
- Urinary urgency or frequency
- Unexplained weight loss or gain
- Fatigue
- Back pain
O que fazer: Elevated CA-125 requires clinical correlation. In postmenopausal women with an adnexal mass, elevated CA-125 strongly suggests malignancy and warrants surgical evaluation. In premenopausal women, benign causes should be excluded first. For patients with known ovarian cancer, serial CA-125 measurements are used to assess treatment response—a 50% decline correlates with response, while a doubling from nadir suggests progression. Additional imaging (transvaginal ultrasound, CT) and possibly further biomarkers (HE4, ROMA score) may be ordered.
O que significam níveis baixos de CA-125
Causas comuns
- Normal physiological state (no clinical concern)
- Successful treatment of ovarian cancer
- Non-mucinous ovarian cancers may not produce CA-125
Possíveis sintomas
- No symptoms are associated with low CA-125
O que fazer: Low or undetectable CA-125 is normal and generally reassuring. In ovarian cancer patients, declining CA-125 toward normal during chemotherapy indicates treatment response. However, a normal CA-125 does not exclude ovarian cancer—some histological subtypes (mucinous, clear cell) may not elevate CA-125 even in advanced disease.
Quando o exame de CA-125 é recomendado?
- Monitoring treatment response in epithelial ovarian cancer
- Surveillance for ovarian cancer recurrence after treatment
- Evaluating an adnexal mass in postmenopausal women
- Screening high-risk women (BRCA1/2 mutation carriers) in combination with ultrasound
- Assessing response to neoadjuvant chemotherapy in ovarian cancer
Perguntas frequentes
Biomarcadores relacionados
Referências e abordagem de revisão
As páginas do glossário de biomarcadores são explicações educativas e devem ser interpretadas junto com as faixas de referência e observações fornecidas pelo seu laboratório e pelo seu médico. Para conhecer nossos padrões editoriais e processo de revisão, veja nossa Política editorial e a nossa revisão de conteúdo.
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Enviar resultados de exames →Aviso médico: Estas informações são apenas educativas e não substituem orientação, diagnóstico ou tratamento médico profissional. As faixas de referência podem variar entre laboratórios. Sempre converse com seu profissional de saúde sobre a interpretação dos seus resultados específicos.