low-grade serous ovarian cancer
Low-Grade Serous Ovarian Cancer (LGSOC) is a rare type of ovarian cancer that disproportionately affects younger women. It’s the fourth most common type of ovarian cancer accounting for 2 to 5% of diagnoses. About half of all people diagnosed with LGSOC are younger than 45 years of age. It is usually found when it has spread beyond the ovaries to lymph nodes or the abdominal lining.
LGSOC is a distinct cancer that is unrelated to the more common high-grade serous ovarian cancer.
The term ‘low-grade’ refers to its appearance under a microscope. It means the cancer cells look more similar to normal (uncancerous) cells and divide slower than ‘high-grade’ cells. Low-grade serous ovarian cancer (also known as low-grade serous carcinoma) develops in the serous epithelium, which lines the ovaries, fallopian tubes and peritoneum. When it is found in the peritoneum, it may be referred to as low-grade serous peritoneal cancer.
About this guide
This guide discusses low-grade serous ovarian cancer and should be read alongside our comprehensive Ovarian Cancer Guide, which provides more general information about ovarian cancer, treatment, side effects and support in New Zealand.
Symptoms
Low-grade serous ovarian cancer symptoms are similar to those caused by other types of ovarian cancer and may include any of the following:
- bloating
- eating less and feeling fuller
- abdominal/pelvic/back pain
- needing to pee more or urgently
- bowel habit changes
Fatigue, painful intercourse, abnormal vaginal bleeding, and unexplained weight change are also possible.
Risk factors
Borderline tumours
Low-grade serous ovarian cancer can develop spontaneously or from a pre-cancerous condition called a borderline tumour (also known as tumours of low malignant potential).
The risk of developing LGSOC from serous borderline tumours is rare when the borderline tumours are found at the earliest stage, but at least two in 10 people with advanced-stage borderline tumours will go on to develop LGSOC in their lifetime.
Other risk factors
Unlike some ovarian cancers, low-grade serous ovarian cancer does not seem to run in families. Less than 6% of people with low-grade serous ovarian cancer have a mutation in the BRCA gene, and this is thought to be an incidental finding, rather than one that leads to the development of the cancer.
Genetic testing
In New Zealand people are eligible for publicly funded genetic testing if they have a 10% or higher chance of having a hereditary (inherited) genetic mutation, like BRCA. Whether someone with LGSOC meets this threshold will depend on their personal and family history of cancer. BRCA mutations can increase the risk of ovarian, breast and other cancers and this risk can be passed through families. If genetic testing finds a hereditary cancer condition like BRCA there may be actions a person and their family can take to reduce their risk of cancers. If someone does not qualify for publicly funded testing, they can choose to pay for these tests privately.
Find out more about hereditary risks and genetic testing.
Investigations and diagnosis
If someone has signs or symptoms of ovarian cancer, their doctor may decide to perform a physical exam, and additional testing. Ovarian cancer is usually detected though a CA-125 blood test and imaging like an ultrasound.
LGSOC diagnosis can be prolonged for some people because the symptoms can be vague, non-specific and gradual, and may be attributed to other conditions – delaying testing. A 2023 international survey of people living with LGSOC found that from the time of first experiencing symptoms, it took a median of 1.5 years (average 2.9 years) to get a diagnosis.
If ovarian cancer is suspected, a sample of the cancer needs to be examined under a microscope by a pathologist to confirm the diagnosis and specific type of ovarian cancer. The pathologist looks at the appearance of the cancer, and for other changes. Low-grade serous ovarian cancer cells have normal (also known as ‘wild-type’) TP53 protein staining and usually express estrogen receptors (ER+).
Because LGSOC is a rare diagnosis, sometimes the pathologist will get a pathology second opinion in New Zealand or overseas.
Tumour testing
Tumour testing (also known as genomic testing) refers to testing a sample of the cancer to look for gene changes (mutations) and other molecular features that make cancer cells different from normal cells. This testing looks for changes that occur in the cancer itself (called somatic change), not changes inherited from parents.
MAP-Kinase mutations such as KRAS, BRAF and NRAS occur in approximately 50% of people with low-grade serous ovarian cancer. There is some evidence to suggest that people with these types of mutations may on average have better prognosis and also respond better to a type of unfunded medication called MEK inhibitors. But this is ‘on-average’ when looking at a large group of people. The presence or absence of a mutation can not predict with certainty what will happen to an individual, and some people without these mutations still respond to MEK inhibitor treatment.
Tumour testing for low-grade serous ovarian cancer is not routinely offered in New Zealand because it is unlikely to change treatment recommendations.
Staging
Staging is a standardised way to describe the spread of cancer. The stage LGSOC is diagnosed at will influence what treatment is recommended.
LGSOC, like other ovarian cancers, is staged according to the FIGO staging recommendations.
Stage 1A: Growth is limited to one ovary with no tumour on the outside surface.
Stage 1B: Growth is limited to both ovaries with no tumour on outside surfaces.
Stage 1C: Tumour is either stage IA or IB, but with tumour on surface of one or both ovaries, or rupture of the tumour before or during surgery, or cancer cells found in ascites (fluid in the abdomen) or washings taken during surgery.
Stage 2: The cancer has spread to the uterus or other nearby organs in the pelvis.
Stage 3: The cancer has spread to the lymph nodes or upper abdominal lining.
Stage 4: The cancer has spread to distant organs, such as the lungs or liver.
Low-grade serous ovarian cancer is most commonly diagnosed when it is stage 3.
Treatment
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.
Fertility considerations
Surgical removal of both ovaries and the uterus causes infertility.
Sometimes, if the cancer is contained within one ovary, it may be possible to have fertility-sparing surgery where an unaffected ovary (+/- the uterus) are retained. However, because low-grade serous ovarian cancer is a hormonally driven cancer, the risks associated with this management and any pregnancy are unknown.
Fertility treatment to extract eggs prior to or following surgery is also sometimes an option. An aromastase inhibitor (such as letrozole) is usually given alongside gonadotropins during treatment to reduce exposure to estrogen, without compromising the effectiveness of the fertility treatment. Fertility treatment may be government-funded for people diagnosed with cancer subject to certain criteria.
If you are interested in fertility sparing surgery and/or egg extraction, talk to your gynaecological oncologist to see if this is an option for you.
Medical treatment
Generally speaking treatment will involve:
Stage 1A/B:
- observation only following surgery
Stage 1C:
- observation,
- or chemotherapy (3-6 cycles) followed by hormone therapy,
- or hormone therapy on its own
Stage 2-4:
- chemotherapy (6 cycles) followed by hormone therapy maintenance,
- or chemotherapy (6 cycles) with bevacizumab, followed by bevacizumab maintenance,
- or hormone therapy maintenance on its own
In 2026 a clinical trial called NRG-GY019 published results showing chemotherapy followed by a type of hormone therapy called letrozole works better than letrozole alone for stage 2-4 LGSOC, when there is visible cancer remaining after surgery.
About the treatments:
Chemotherapy is a medical treatment targets fast growing cancer cells. The chemotherapy used is paclitaxel and carboplatin.
Hormone therapy blocks cancer access to estrogen. Low-grade serous ovarian cancer can use estrogen to spread and grow. Usually an aromatase inhibitor such as letrozole or anastrozole is used. Aromatase inhibitors alone are given post-menopause. If an ovary is retained in pre-menopause, a GnRH agonist like Zoladex will be used to induce medical menopause, in addition to an aromatase inhibitor.
Bevacizumab is an anti-VEGF monoclonal antibody that stop the cancer growing new blood vessels. It is more commonly used in Europe, and less commonly in New Zealand (and Australia and North America). In New Zealand it is funded for stage 3b/c and stage 4 ovarian cancer subject to certain criteria.
Neoadjuvant treatment
Neoadjuvant treatment is when medical treatment is used to shrink the cancer before surgery. It should only be used in LGSOC when surgery is very unlikely to remove all or most of the visible cancer; or in patients who have significant co-morbidities (other serious medical conditions) where surgery is not safe or in their best interest. Usually chemotherapy is used, sometimes with bevacizumab.
Researchers are investigating other potential future treatments including CDK4/6 inhibitors with hormone therapy, and MEK inhibitors with hormone therapy.
Recurrance of LGSOC
Recurrence is when low-grade serous ovarian cancer comes back after primary treatment. Treatments for recurrence may include:
- Surgery
- Chemotherapy
- Hormone therapy
- Bevacizumab
- Clinical trials
- MEK inhibitors (currently unfunded in NZ)
- Other off-label treatments*
* ’Off-label’ means that a treatment is approved for a disease, but not low-grade serous ovarian cancer. Strictly speaking most treatments used in LGSOC are used off-label (such as hormone therapy which has been borrowed from breast cancer). But off-label can also be used to refer to experimental treatments that are being researched.
Prognosis
The following section discusses what is likely to happen over time with low-grade serous ovarian cancer (prognosis). Prognosis statistics are general and describe what happened to groups of people in the past, who may or may not have had similar characteristics and treatments as you. Your doctor is the best person to help you understand your specific prognosis but they can’t say for certain how you will do. Not everyone wants to know the statistics – you are welcome to skip this section.
Stage 1 LGSOC
Early-stage LGSOC has a very good prognosis; it is estimated that 90% of people diagnosed with Stage IA/B and at least 50% of people diagnosed with Stage IC will experience cure, meaning, the cancer never returns after treatment.
Stage 2-4
For people with stages 2 to 4 LGSOC, the median survival is approximately 10-12 years. This means that with current treatments, half of all people with LGSOC live 10-12 years or less, and half live longer.
Recurrence rates, where the cancer comes back after treatment, have traditionally been quoted as at least 70%. However, a study from 2022 (view summary here) has suggested that recurrence rates seem to be improving with modern treatments and may be closer to 50%.
Research and clinical trials for LGSOC
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. You can ask your doctor whether there are any clinical trials that you can participate in.
The LGSOC Initiative
OCFNZ’s founder Jane Ludemann was diagnosed with LGSOC in 2017, and LGSOC continues to be a special focus for our organisation. In addition to our support of LGSOC research within New Zealand, we host a global project called the Low-Grade Serous Ovarian Cancer Initiative.
The LGSOC Initiative’s mission is to radically improve the survival of women with low-grade serous ovarian cancer through research, and to provide good information to enable and empower them to make informed decisions about their care.
Through the LGSOC Initiative, we set up the first online pathways for people in New Zealand, Australia, Canada, the UK and US to donate and fundraise directly for LGSOC research. To date our community have helped raise over $500,000 for LGSOC research around the world.
On our LGSOC Initiative website you can find LGSOC specific resources including:
- How to join our Low-Grade Serous Ovarian Cancer Peer Support Group to connect with other people with a diagnosis of LGSOC
- Guides to hormone therapy, and resources on side effect management including joint pain, and sexual side effects
- Information on how to find a clinical trial
- Interviews with world experts
Information about the research we are supporting
LGSOC webinar presented by Dr David Gershenson
Find out more information about ovarian cancer.
Note: this content has been reviewed by a gynaecological cancer specialist. Information is provided for general use and should not be a substitute for professional medical advice.
Last reviewed: July 2026