low-grade serous ovarian cancer
What is low-grade serous ovarian cancer?
Low-grade serous ovarian and peritoneal cancer (LGSOC) is a type of ovarian cancer that disproportionately affects younger women and has poor response rates to chemotherapy. It is usually found after the cancer has spread to other parts of the body when it is more challenging to treat.
Low-grade serous ovarian cancer is associated with a precancerous condition called borderline tumours. It is unrelated to the more common and similarly named high-grade serous ovarian cancer (HGSOC).
Low-grade serous ovarian cancer is usually treated with surgery and medical treatments, including chemotherapy, hormonal therapy, targeted therapies and clinical trials.
How did low-grade serous ovarian cancer get its name?
Low-grade serous ovarian cancer got its name from:
- The medical terms that describe what it looks like under a microscope
- The particular cells it affects
- Where it starts growing
Grading is a medical term that describes the appearance of cells under a microscope. It is based on the amount of nuclear atypia in the cells, and secondarily the mitotic count. By definition, low-grade serous ovarian cancer is a “low-grade” cancer. Essentially, this means the cancer cells look more normal and grow slower than high-grade cancer cells.
“Serous” means the cancer forms in the slippery cells that cover the outside (epithelium) of the ovary and peritoneum.
The cancer is labelled “ovarian” or “peritoneal” depending on whether the first cancer growth was in the ovaries or peritoneum. The medical term for low-grade serous ovarian and peritoneal cancer is low-grade serous carcinoma, but it’s more common to use low-grade serous ovarian cancer for both.
Image: Abdominal anatomy
How common is low-grade serous ovarian cancer?
Low-grade serous ovarian cancer is the 4th most common type of ovarian cancer. Out of every 100 people diagnosed with ovarian cancer, between two and five will have LGSOC, making it a rare cancer. It’s estimated that there are between 65,000 and 160,000 women are currently living with LGSOC around the world.
How is low-grade serous ovarian cancer diagnosed?
Low-grade serous ovarian cancer can be detected with a CA-125 blood test and an ultrasound (or other imaging). Like other ovarian cancers, there is no screening test and testing is only indicated if there are symptoms.
If ovarian cancer is suspected, a sample of the cancer is needed to confirm the exact diagnosis; this is removed by surgery or, less often, a biopsy.
What are the symptoms of low-grade serous ovarian cancer?
Most, but not all, people experience symptoms before they are diagnosed. Symptoms of low-grade serous ovarian cancer and their frequency include:
- Abdominal, pelvic or back discomfort/pain (76%)
- Stomach bloating (68%)
- Fatigue (61%)
- Frequent or urgent need to urinate (54%)
- Repeated changes to bowel movements (49%)
- Nausea, vomiting, heartburn, gas, burning or indigestion (41%)
- Loss of appetite or eating less and feeling fuller (36%)
- Painful sexual intercourse (31%)
- Vaginal discharge, bleeding or spotting not related to menstrual cycle (25%)
- Unexplained weight loss (11%)
Source: LGSOC Patient Impact Survey Research Findings
Compared to other ovarian cancers, LGSOC can take much longer to be diagnosed. Half of all people with LGSOC have symptoms for three years or longer before they are diagnosed.
What is the average age at diagnosis?
The median age of diagnosis for low-grade serous ovarian cancer is about 45 years. This means that half of all people are older than, and half younger than 45 when they are diagnosed, some of whom are as young as teenagers. This is about twenty years younger than ovarian cancer overall.
What are the risks and causes of low-grade serous ovarian cancer?
The risk factors and causes of low-grade serous ovarian cancer are unclear. It’s very likely that most LGSOC is due to bad luck, rather than anything a person did or did not do.
Borderline tumours
LGSOC can develop ‘de novo’ (spontaneously) or from a borderline tumour.
Borderline tumours are a pre-cancerous ovarian growth. They are non-invasive, which means they grow on top of surfaces, not into deeper tissues like LGSOC. Serous borderline tumours can turn into LGSOC, although this rarely happens when they are found and treated early. But, up to 20% of women with advanced borderline tumours will get low-grade serous ovarian cancer in their lifetime.
About 60% of women diagnosed with low-grade serous ovarian cancer will also have a borderline tumour. The presence of a borderline tumour does not affect LGSOC treatment.
BRCA mutations
Two to four in 100 people with LGSOC carry an inherited BRCA 1 or BRCA 2 mutation. Unlike high-grade serous ovarian cancer, it is unclear whether the mutation contributes to the development of the cancer.
Differences between low-grade serous and high-grade serous ovarian cancer
Until 2004 low-grade serous and high-grade serous ovarian cancer were thought to be very similar. We now know they are each unique and completely different cancers. Examples of how they differ include their grade, development, genomics, inheritance risk, age at diagnosis, frequency, response to chemotherapy and survival.
Grade
Low-grade serous ovarian cancer is low grade. High-grade serous ovarian cancer is high grade. Generally speaking, LGSOC does not turn into HGSOC, however in rare cases, people can be diagnosed with both at once.
Development
LGSOC is associated with borderline tumours. HGSOC is associated with serous tubal intra-epithelial carcinoma (STIC). LGSOC starts in the ovary or peritoneum. HGSOC is more likely to start in the fallopian tube.
Genomics (gene mutations in the cancer)
Low-grade serous ovarian cancer almost always has a wild type TP53 gene. Wild type means the gene is normal (not mutated). High-grade serous ovarian cancer almost always has a mutated TP53 gene. MAP Kinase mutations like KRAS, BRAF and NRAS are common in LGSOC. BRCA mutations are common in HGSOC.
Inheritance risk
As far as researchers know, LGSOC doesn’t run in families. HGSOC can be inherited.
Age at diagnosis
On average people with LGSOC are about twenty years younger than those with HGSOC.
Frequency
Low-grade serous is an uncommon ovarian cancer. High-grade serous is the most common ovarian cancer. Out of every 100 women diagnosed, approximately two have LGSOC and about 65 have HGSOC
Chemotherapy response
Response rates (tumour shrinkage) to chemotherapy are low in LGSOC and high in HGSOC. For LGSOC, only 2-23% of patients respond to neoadjuvant chemotherapy*. This is much lower than the 80-90% response rate for HGSOC. Because of this, surgery may need to be more aggressive in LGSOC.
*Neoadjuvant chemotherapy is when chemotherapy is given before surgery, with the intent of shrinking the cancer.
Recurrence and survival statistics
The following statements make broad generalisations about recurrence and survival in low-grade serous and high-grade serous ovarian cancer. They are based on average outcomes of groups of people in past studies. They do not account for people’s unique circumstances.
Recurrence
Both low-grade serous and high-grade serous ovarian cancer often return after treatment. For every 100 people diagnosed, more than 70 will have their cancer come back.
Survival
On average, people with LGSOC live twice as long with the disease as those with HGSOC. However, because HGSOC typically affects older people, people with HGSOC are more likely to live to an older age compared to those with LGSOC.
Stages of low-grade serous ovarian cancer
Staging is a medical term. It describes where low-grade serous ovarian cancer has spread to at diagnosis. Where the cancer is found affects treatment and it also affects the chance of treatment working.
About 70% of people are diagnosed at stage III, and 10% of people are diagnosed at stage I, II and IV respectively.
Treatments for low-grade serous ovarian cancer
Low-grade serous ovarian cancer is usually treated with surgery followed by medical treatments.
To date, there have been very few clinical trials in LGSOC. Many treatment decisions are made based on small retrospective studies and doctors’ personal experiences. The quality of evidence for medical decision making is lower than in common cancers.
Surgery
The purpose of surgery is usually to remove visible cancer and find out how far the cancer has spread (staging). Normally this involves the removal of the ovaries, fallopian tubes, uterus and omentum. Depending on where the cancer has spread, some of the bowel, liver, lymph nodes or other organs may also be removed.
If the cancer is found at stage I, surgery may be the only treatment required.
Medical treatment
Medical treatment for newly diagnosed low-grade serous ovarian cancer this usually consists of:
- Chemotherapy, followed by hormonal therapy, or
- Hormonal therapy, or
- Chemotherapy with bevacizumab (stages III-IV)
Recommendations depend on stage at diagnosis. The preferred treatment also varies by country and doctor.
Neoadjuvant treatment
Treatments for recurrence
Recurrence is when low-grade serous ovarian cancer comes back after treatment. Treatments for recurrence may include:
- Surgery
- Chemotherapy
- Hormonal therapy
- Bevacizumab
- MEK inhibitors
- Clinical trials
Why is chemotherapy still used in low-grade serous ovarian cancer if response rates are low?
Chemotherapy has a role in treating LGSOC despite low response rates. Response rate (RR) refers to the proportion of people who have their cancer shrink with treatment. A recent study suggests chemotherapy may work much better after surgery (58% RR) than before surgery (2-23% RR), or if the cancer comes back (2-25% RR).
Even when chemotherapy does not shrink cancer, it may still stop it growing. There are limited treatment alternatives to chemotherapy and for some people chemotherapy can be helpful. It is not possible to predict ahead of time how someone with LGSOC will respond to chemotherapy.
Visit our guide to LGSOC to learn more about treatments
Survival and recurrence statistics for low-grade serous ovarian cancer
Survival rates show how long people with low-grade serous ovarian cancer live after diagnosis. Recurrence rates show how often low-grade serous ovarian cancer comes back after treatment. If the cancer never comes back, it is considered cured.
Survival and recurrence statistics say what happened to groups of people in the past. They are general in nature and do not account for individual circumstances.
Survival and recurrence statistics differ based on many factors, including the stage at diagnosis.
Recurrence statistics
Most people with stage Ia or Ib LGSOC will experience cure. This is much less likely when the cancer has spread beyond the ovaries. In all, at least 70% of people with advanced low-grade serous ovarian cancer have their cancer come back after treatment. This is most likely within the first five years, but it is possible to have a recurrence after five years.
Survival statistics
The median survival for low-grade serous ovarian cancer is 10-12 years. This means that half of all people diagnosed with LGSOC will live longer, and half less. Some of the people who live longer will never recur and will have a normal life expectancy.
Visit our guide to LGSOC for more detailed recurrence and survival statistics.
Research and clinical trials for low-grade serous ovarian cancer
Researchers are working to improve the survival of LGSOC. This includes:
- Repurposing treatments from other diseases
- Making existing treatments work better
- Finding new treatments
- Identifying biomarkers to target treatments to individuals
Clinical trials are a type of research people with low-grade serous ovarian cancer can volunteer for. They help doctors understand how better to treat LGSOC and can give people access to new treatments that they otherwise could not access.
Learn more about:
Living with low-grade serous ovarian cancer
LGSOC can hugely impact a person’s life, affecting daily activities, relationships, jobs, and mental health.
Common challenges reported by people with LGSOC include:
- Living with uncertainty
- Treatment side effects
- Anxiety or worry
- Feeling like life revolves around cancer
Things that people with LGSOC have found helpful in improving their quality of life include:
- Speaking to a psychologist, counsellor or therapist
- Joining a LGSOC support group
- Regular exercise
- Seeing a specialist experienced in LGSOC
- Practising self-kindness
- Setting short term goals to look forward to
- Reevaluating their priorities
- Physical therapy and pelvic floor physiotherapy
- Complementary therapies including yoga, meditation and time in nature/with animals
Don’t put too much pressure on yourself. You didn’t cause this and you can’t be expected to fix it all on your own. You’re going to get lots of advice from well-meaning people about diet and lifestyle but you need to follow your intuition and listen to your body, you are unique and there is no one-size-fits-all approach.
Jenny
Last update: 8 August 2024.
This article has been medically reviewed by an expert in low-grade serous ovarian cancer.