Ovarian cancer begins in the ovaries, the two small almond-shaped organs in the female reproductive system that produce eggs and hormones1. It is a relatively rare cancer (about 22,000 new US cases/year) that mostly affects postmenopausal women2,3. Most ovarian tumors (about 90%) are epithelial carcinomas on the ovary’s surface4. (Cancers that look like ovarian cancer can also start in the fallopian tubes or the lining of the abdomen – these are treated in the same way.) In its earliest stages, ovarian cancer may be confined to one ovary and cause no symptoms.
Risk factors of Ovarian Cancer
Exact causes of ovarian cancer are unknown, but doctors have identified many risk factors. The biggest is family history – having a mother, sister, or daughter with ovarian (or breast) cancer – especially when due to inherited BRCA1/BRCA2 gene mutations5.
Other important factors include older age (most cases occur after age 50), having had no children or a first pregnancy after age 30, and conditions like endometriosis.
Lifetime hormone exposure plays a role: long-term use of menopausal hormone therapy and obesity modestly increase risk, whereas oral contraceptives (birth control pills) greatly reduce risk6.
(For example, women who have taken birth control pills have a 30–50% lower risk of ovarian cancer than those who never have7.) About 10–20% of ovarian cancers are linked to inherited mutations (chiefly BRCA1/2)8.
Ovarian cancer Symptoms and detection
Early ovarian cancer usually causes no specific warning signs. When symptoms appear, they tend to be vague – bloating, pelvic or abdominal pain, feeling full quickly, or urinary urgency/frequency9,10.
Because these symptoms mimic common benign conditions, ovarian cancer is often not detected until it is advanced11.
In fact, the majority of women are diagnosed at stage III or IV, when the cancer has spread within the abdomen. Routine screening of asymptomatic women (using pelvic exams, transvaginal ultrasound or blood markers like CA-125) has been shown not to reduce mortality12,13.
The U.S. Preventive Services Task Force therefore recommends against ovarian cancer screening in average-risk women14. Women with very high risk (strong family history or genetic mutation) may undergo more intensive monitoring or consider preventive surgery.
Because ovarian cancer often spreads within the abdomen, images of later stages can look very different from early disease.
For example, the diagram above contrasts stage III vs stage IV disease. In stage III, cancer has already spread beyond the ovaries to nearby abdominal organs or lymph nodes15. By stage IV, it has reached distant sites such as the liver, lungs or other organs16.
Prevention of Ovarian cancer
No guaranteed way to prevent ovarian cancer is known, but risk can be reduced. Factors that reduce lifetime ovulation are protective. Taking birth control pills for several years can cut risk in half17.
Every full-term pregnancy, especially before age 30, also lowers risk. For women with BRCA1/2 mutations or very strong family histories, doctors often consider prophylactic oophorectomy (removal of ovaries and tubes) after childbearing.
Such preventive surgery can reduce ovarian cancer risk by over 90%18. Other strategies (like healthy weight, avoiding unnecessary hormone therapy) are prudent but have less impact. Because no screening is effective for most women, awareness of symptoms and prompt evaluation of persistent signs is important.
Ovarian cancer Treatment
Ovarian cancer is usually treated with a combination of surgery and chemotherapy 19. The goal of surgery is maximal tumor removal (cytoreduction or “debulking”). In early-stage disease, the surgeon may remove only the affected ovary and tube (preserving the uterus and the other ovary if fertility is desired)20.
In more advanced cases, the standard procedure is a total hysterectomy with removal of both ovaries and tubes, nearby lymph nodes, and the omentum (the fatty apron over the intestines)21.
After surgery, most patients receive systemic chemotherapy, typically a platinum drug (carboplatin or cisplatin) plus a taxane (paclitaxel), to kill any microscopic residual cancer22. Some centers use heated intraperitoneal chemotherapy (HIPEC) at the time of surgery in select cases.
Other options may be used for specific situations: for example, hormone therapies for certain slow-growing tumors, or targeted therapies (like PARP inhibitors for BRCA-mutant cancers)23.
Radiation therapy is rarely used for ovarian cancer nowadays24. Throughout treatment, supportive (palliative) care is offered to manage symptoms and side effects. Many women respond well to first-line therapy, but ovarian cancer has a high recurrence rate, so follow-up care is important.
Ovarian Cancer Subtypes
Ovarian cancer is a heterogeneous disease. Epithelial tumors arising from the ovarian surface lining account for >90% of cases25.
The most common and aggressive subtype is high-grade serous carcinoma; other epithelial subtypes include low-grade serous, endometrioid, clear cell, and mucinous carcinoma26. (Together these five histotypes cover essentially all epithelial ovarian cancers.)
The remaining cases include germ cell tumors and sex-cord stromal tumors (such as granulosa cell tumors), which are much rarer24. Each subtype has distinct molecular features.
For example, almost all high-grade serous tumors carry mutations in the TP53 gene. Roughly 15–25% of high-grade serous tumors arise in women with germline BRCA1 or BRCA2 mutations25.
Other hereditary syndromes (e.g. Lynch syndrome) can underlie endometrioid and clear cell cancers. These genetic factors (e.g. BRCA mutations) are important predictors of treatment response.
The female reproductive anatomy is shown above. Ovaries (5) lie beside the uterus (6) and connect to the uterus via fallopian tubes (4). Ovarian cancer develops in these ovaries or related structures26. High-grade serous cancers may actually originate in the fallopian tube fimbriae before involving the ovary27.
Pathogenesis and spread of Ovarian cancer
Most ovarian cancers spread early within the peritoneal cavity. In the tubal-origin model, malignant cells from a primary fallopian tube lesion (STIC) exfoliate and seed the peritoneal surfaces.
Tumor cells then implant on the omentum, bowel, and diaphragm28. This explains why many patients have diffuse abdominal disease at diagnosis. Ovarian cancers also invade locally and can metastasize via lymphatics and blood at later stages.
Understanding this biology has led to staging and treatment strategies focused on surgical cytoreduction.
FIGO Staging of Ovarian cancer
Ovarian cancer is staged using the FIGO system (similar to AJCC TNM), with stages I–IV based on extent of spread29.
Stage I is cancer confined to one or both ovaries30. Stage II indicates extension to the pelvis (e.g. uterus, tubes, or bladder/rectum)32. In stage III, there are peritoneal implants outside the pelvis (e.g. on the omentum or liver capsule) and/or spread to retroperitoneal lymph nodes33.
Stage IV means there are distant metastases – for example, cancer cells in the pleural fluid or in organs beyond the abdomen (lung parenchyma, liver parenchyma, or extra-abdominal lymph nodes)34.
Figure 1: FIGO stage III ovarian cancer. The cancer (red) involves both ovaries and has spread to the omentum and lymph nodes35. In this diagram, both ovaries (center) have tumors, and red spots show implants on the omentum and abdominal lining (stage IIIC). By contrast, stage I would have cancer only inside one ovary36.
Figure 2: FIGO stage IV ovarian cancer. Cancer (red) has spread to the pleura (lung lining) and distant lymph nodes38. In stage IV, tumor cells have metastasized outside the peritoneal cavity (here showing lung involvement).
Ovarian cancer Diagnosis
Evaluation starts with imaging (transvaginal ultrasound, CT/MRI) and serum markers (CA-125, HE4), but tissue biopsy is required for definitive diagnosis and histologic typing. CA-125 is often elevated in ovarian cancer, especially serous types, and is used to monitor response to therapy, but it is not specific enough for early detection in average-risk women39.
Surgical exploration (laparoscopy or laparotomy) provides staging information and tumor specimens.
Treatment pathways for Ovarian cancer
Standard initial therapy is cytoreductive surgery followed by platinum-based chemotherapy. Upfront surgery aims for no visible tumor left (optimal debulking). Early-stage disease (stage I) may be managed with surgery alone, while stages II–IV require systemic chemotherapy.
The usual regimen is carboplatin plus paclitaxel (often 3-week cycles)40. For example, a patient with stage III disease would undergo maximal debulking and then 6–8 cycles of chemo. Some patients receive neoadjuvant chemotherapy (chemo first) if initial surgery is not feasible, followed by interval debulking.
Targeted therapies are integrated based on tumor biology. Anti-angiogenic therapy (bevacizumab) is approved for advanced ovarian cancer. PARP inhibitors (e.g. olaparib, niraparib) are highly effective as maintenance therapy for patients with BRCA-mutant or homologous recombination–deficient tumors.
Hormonal therapies (aromatase inhibitors, tamoxifen) may be used for low-grade or platinum-resistant cases that express hormone receptors41. Immune checkpoint inhibitors are under study but not standard outside clinical trials. If cancer recurs, treatment depends on the cancer’s platinum-sensitivity: options include retreatment with platinum-based chemo for sensitive relapse or non-platinum drugs (liposomal doxorubicin, etc.) for resistant disease, often combined with targeted agents.
Prognosis and follow-up: Prognosis varies by stage and biology. Early-stage cancers have high cure rates, but advanced-stage (III-IV) 5-year survival remains modest. FIGO stage, residual tumor after surgery, and performance status are key prognostic factors. Follow-up includes periodic exams, imaging, and tumor markers to detect recurrence. Research continues to improve early detection and develop new therapies.
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