High Grade Serous Carcinoma

High grade serous carcinoma is the most common type of ovarian cancer, accounting for approximately 75% of epithelial ovarian cancers. Because it is the most common type of ovarian cancer, it is often the default type that’s referenced in discussions of ovarian cancer, unless another type is specified. 

Up until recently, it was thought that ovarian cancers develop in the epithelium (the cells lining the surface) of the ovaries. Researchers now believe that many cases of high grade serous ovarian carcinoma (HGSOC) — which are a subtype of epithelial ovarian cancers, along with low-grade serous ovarian cancer, fallopian tube cancer, and primary peritoneal cancer — actually originate in the epithelium of the fallopian tubes.

What does high grade carcinoma mean?

In medical terminology, a tumor’s grade refers to the type of cells that make up a tumor, based on how the cells and tissue look under a microscope. When high grade serous carcinoma cells and tissue are viewed under a microscope, they appear highly abnormal compared to healthy cells and tissue. High grade carcinoma tumors are also poorly differentiated, meaning they do not have a clear structure or pattern. This blending together indicates that the tumor cells organize abnormally, and tend to grow quickly. 

The “high grade” in high grade serous ovarian carcinomas refers to ovarian carcinomas that are classified as Grade 3. “Serous” means that the tumor arose from the serous membrane, in the epithelial layer in the abdominopelvic cavity. 

Is high grade serous ovarian carcinoma curable?

Patients with HGSOC often respond well to treatment, and can experience remission — however, it is common for high grade serous patients to recur over a period of time, with the majority of recurrences occurring within three years. 

Outcomes for patients with this type of ovarian cancer vary on an individual basis; currently, the median overall survival for patients with high grade serous ovarian carcinoma is about 40 months. 

Its status as the most common type of ovarian cancer makes high grade serous ovarian carcinomas an especially intense focus of scientific studies, and the relatively large cohort of researchers committed to better understanding and tackling the challenges of this form of the disease means more breakthroughs, at a quicker pace, for HGSOC than for many other types of ovarian cancer.

For patients with high grade serous ovarian cancer — whether first-time diagnosis, recurrence, or NED (no evidence of disease) on a maintenance regimen — it may be beneficial to look into available clinical trials. Ongoing scientific studies are at the forefront of finding newer, more effective treatments, and many patients have benefitted from participating in these groundbreaking trials.

Learn more about clinical trials, and visit OCRA’s clinical trial finder.

How fast does high grade serous carcinoma grow?

High grade serous carcinoma tends to grow quickly. It is often diagnosed in advanced stages (Stage III or IV), meaning that the cancer cells have already spread outside of the ovaries. Recent studies have shown that high-grade serous carcinomas that begin with a primary tumor in the fallopian tubes take an average of 6.5 years to reach the ovaries, after which they spread to other areas quite quickly.

Advanced stage carcinomas generally spread to the peritoneum (the lining of the organs of the pelvis and abdomen) first, and can lead to fluid buildup in the peritoneal cavity — a condition called ascites, which can cause abdominal bloating, and in some cases is the first noticeable symptom of presence of ovarian cancer. Early stage high grade serous carcinoma often does not cause any noticeable signs or symptoms, thus the cancer is often diagnosed at more advanced stages. 

Once they do appear, signs and symptoms of ovarian cancer can include the following:

  • Bloating
  • Pelvic or abdominal pain
  • Difficulty eating or feeling full quickly
  • Urinary symptoms (urgency or frequency)

What are current treatments for patients with high grade serous ovarian carcinoma?

Standard first-line treatment for high grade serous ovarian carcinoma typically consists of debulking surgery — otherwise known as cytoreductive surgery — which involves removal of as much of the tumor as possible, followed by intravenous paclitaxel/platinum-based chemotherapy, and often subsequent maintenance therapy. 

(Note: Patients whose debulking surgery is performed by a gynecologic oncologist have been shown to experience better outcomes than those whose surgery is performed by other medical professionals. Learn more about gynecologic oncologists.)

In the past several years, a new class of targeted therapy called PARP inhibitors, have become valuable maintenance therapy options for some patients, especially those with BRCA mutations. In 2020, PARP inhibitors received FDA approval as first-line therapy for a subset of patients with advanced ovarian cancers, and has been shown to significantly improve progression-free survival. 

For patients who have completed chemotherapy a minimum of one year prior, and who have fewer than three sites of disease, new research also points to improved survival rate for those who undergo secondary debulking surgery to treat recurrent ovarian cancer.

Further, a recently published study shows that hyperthermic intraperitoneal chemotherapy (HIPEC) immediately after debulking surgery can improve survival rates for stage III epithelial — including high grade serous — ovarian cancer patients.

When recommending treatments for high grade serous ovarian carcinoma, a physician will consider factors like genetic mutations, the stage of the cancer at diagnosis, and more.

High grade serous ovarian carcinoma studies

OCRA-funded researchers are working hard to solve the mysteries of high grade serous ovarian carcinoma — studying tumor microenvironments, identifying cells of origin, exploring potential drug targets, and more — with a singular focus on finding a cure for the most common type of ovarian cancer.  

View all of the scientific studies funded by OCRA, and learn how grantees are making progress against high grade serous ovarian cancer. 

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