CompletedInterventional

International Collaborative Ovarian Neoplasm studies (1): A trial of adjuvant chemotherapy for early-stage ovarian cancer

The ICON1 study is looking at the best timing for chemotherapy in women who have early-stage ovarian cancer. After surgery to remove the tumour, it is not always clear whether chemotherapy is needed straight away, or if it is safe to wait. Participants are placed into one of two groups. One group receives chemotherapy shortly after their operation. The other group is monitored closely and only receives chemotherapy if the cancer shows signs of returning. Researchers want to see if having chemotherapy immediately helps women live longer and prevents the cancer from coming back, compared to waiting. By comparing these approaches, the study aims to help doctors understand who truly benefits from early chemotherapy and who might be safely spared unnecessary treatment and its side effects.

At a glance

Status

Completed

Sponsor

Medical Research Council (MRC) (UK)

Enrolment target

2,000

Start

01 Jan 1991

Estimated completion

21 Jan 2000

Cancer

What is this study about?

Ovarian cancer affects the ovaries, which are part of the female reproductive system. When the cancer is found at an early stage, surgery is usually the main treatment to remove the tumour. However, doctors often face a difficult question after surgery: should a patient have chemotherapy straight away to kill any remaining cancer cells, or is it better to hold off?

For many women with early-stage ovarian cancer, surgery alone may completely remove the cancer. In these cases, having chemotherapy right away might cause unpleasant side effects without offering extra benefit. For other women, early treatment might be crucial to stop the cancer from returning. Because doctors cannot always be sure which approach is best, this trial was designed to compare them directly.

In the study, some women receive chemotherapy soon after surgery, while others do not receive it unless follow-up tests show the cancer has come back. By following both groups over time, doctors can see whether immediate chemotherapy improves overall survival and quality of life.

The results of this research help shape standard care across the NHS and worldwide. They provide clearer guidance so future patients receive chemotherapy only when it provides a clear benefit, avoiding unnecessary treatments whenever possible.

Key takeaways

The trial compares immediate chemotherapy against waiting and watching in early-stage ovarian cancer.
It helps doctors learn whether early chemotherapy improves survival or causes unnecessary side effects.
Participants are randomly assigned to receive chemotherapy straight away or only if needed later.
The study is for females with early-stage cancer who have not had chemotherapy or radiotherapy before.
Taking part is voluntary, and you can withdraw at any time without affecting your NHS care.

Who may be eligible?

This trial is open to females of any age who have been diagnosed with early-stage ovarian cancer and have already had surgery. It is designed specifically for women whose doctors are uncertain whether chemotherapy is definitely needed straight away.

To join, you must not have had any previous cancer, and you must not have had chemotherapy or radiotherapy in the past. You also need to be well enough in your general health to receive chemotherapy safely if you are assigned to that group.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

I am female.
I have been diagnosed with early-stage ovarian cancer.
I have had surgery for my ovarian cancer.
My doctor is unsure whether I need chemotherapy straight away.
I have never had cancer before.
I have not had chemotherapy or radiotherapy in the past.

Answer every question to see your result.

What does participation involve?

If you take part, you will be randomly placed into one of two groups by a computer. One group starts chemotherapy shortly after surgery. This usually involves regular hospital visits over several months to receive medicine through a drip. The other group is watched carefully without immediate chemotherapy. Both groups have regular hospital check-ups, which include physical examinations, blood tests, and scans to monitor health. Follow-up continues for several years to see how you are doing over the long term.

Potential risks and benefits

A potential benefit of joining is that immediate chemotherapy might lower the chance of the cancer returning, while being in the observation group might spare you from treatment side effects. However, there is no guarantee that one approach will work better for you than the other. Chemotherapy can cause side effects such as tiredness, sickness, hair loss, and an increased risk of infections. If you choose to take part, you can change your mind and leave the trial at any time, and your standard NHS care will not be affected.

Locations (1)

Some site locations are approximate. We're improving this — please verify with the trial team before travelling.

MRC Clinical Trials Unit
City only
London, England

Common questions

What is early-stage ovarian cancer?

It means the cancer is contained within the ovaries or pelvis and has not spread to distant parts of the body.

How is it decided which group I am in?

A computer allocates you to a group by chance. This is called randomisation, and it ensures the study results are fair and reliable.

What happens if my cancer returns while in the observation group?

You will be monitored closely with regular tests. If the cancer returns, your doctor will discuss starting chemotherapy and other suitable treatments immediately.

Will taking part cost me anything?

No, all trial treatments, tests, and standard appointments are provided through the NHS.

Can I leave the study if I change my mind?

Yes, you can leave the study at any time without giving a reason, and it will not affect the quality of your regular medical care.

How to find out more

Sarah Wheeler

abc@email.com - Official trial record

Always speak to your GP or specialist before deciding to take part in a study.