- the original treatment did not remove of all the cancer cells and those left behind grew into a new tumor
- some cancer cells have spread elsewhere in the body and started growing there to form a tumor
Cancer can come back after surgery because:
some cancer cells were left behind during the operation
- some cancer cells had already broken away from the primary cancer but were too small to see, known as micrometastases
Surgeons do their best to remove all of the cancer during surgery. But it is always possible to leave behind a small group of cancer cells. The surgeon may recommend more treatment if they feel that there is a risk that the cancer could come back.
The extra treatment might be chemotherapy, radiotherapy, hormone therapy or a targeted cancer drug. These treatments aim to try to control or kill any cancer cells left.
After cancer drug treatment or radiotherapy
Cancer may sometimes come back after cancer drug treatment or radiotherapy. This can happen because the treatment didn’t destroy all the cancer cells.
Chemotherapy drugs kill cancer cells by attacking cells that are in the process of doubling to form two new cells. However, not all the cells in a cancer divide at the same time. Normal cells go into a long rest period between divisions. Cancer cells do too, although the rest period may be much shorter.
Giving chemotherapy in a series of treatments can help to catch as many cells dividing as possible. Cells that were resting when you had your first treatment, may be dividing when you have your next and so will be more likely to die.
But it is unlikely that any chemotherapy treatment kills every single cancer cell in the body. Doctors try to reduce the number of cancer cells as much as possible. The immune system kills off the remaining cells or they may die off.
Radiotherapy makes small breaks in the DNA inside the cells. These breaks stop cancer cells from growing and dividing and often make them die. Normal cells close to the cancer can also become damaged by radiation. If radiotherapy doesn’t kill all of the cancer cells, they will regrow at some point in the future.
Targeted cancer drugs work by ‘targeting’ those differences that help a cancer cell to survive and grow. Some treatments may get rid of a cancer completely. Others may shrink the cancer or control it for some months or years. So a cancer may seem to have gone and may not show up on any scans or blood tests. But there may be a small group of cells that remain in the body. They can start to grow again after a while or when the treatment stops.
Cancers can become resistant to treatment
Sometimes cancer can become resistant to cancer drug treatment. Cancers develop from normal cells that have changed or mutated to become cancerous. The mutation happens in the genes of the cell. These gene changes make the cell behave differently to a normal cell. Cancer cells can continue to mutate so that they become more and more abnormal.
Some mutations can make the cells resistant to cancer drugs such as chemotherapy, targeted cancer drugs or hormone therapy. You can sometimes have a different type of treatment if this happens. But sometimes cancers develop resistance to many drugs at the same time. This is called multi drug resistance.
Scientists have found a group of genetic mutations that they think can cause drug resistance. These mutations mean that the cancer cell can keep the drugs out. The resistant cells have high levels of a substance called p-glycoprotein. P-glycoprotein is a protein found in cell walls. The protein acts as a pump and removes toxins from cells. Cells with high p-glycoprotein levels are very good at keeping cancer drugs out.
Researchers have been looking at drug resistance for almost as long as they have used cancer drugs. To make cancer drug treatment more effective, we need to find a way of overcoming resistance.
Doctors can’t be sure that the cancer has completely gone after treatment. So they may suggest that you have some type of long term treatment. This might include hormone therapy or a targeted cancer drug. This is called adjuvant treatment.
Adjuvant treatment can also be a course of chemotherapy or radiotherapy after surgery. The aim of this treatment is to try to prevent cancer from coming back.
Living with uncertainty
It can be very difficult to live with the fact that your cancer may come back. Even if doctors tell you that they are 95% certain your cancer has gone for good, you may find it very upsetting that no one can say for sure that you’re cured.
Some people find that they can’t stop thinking about it even after the end of their treatment. You might feel a little frightened of planning anything in the future. Or you may feel sad or depressed.
Some types of cancer can come back many years after they were first diagnosed. Some people find it very difficult to cope with this idea, but there are some things you can do to help.
Getting help and support
The Cancer Coach.org is a dedicated health platform that puts patients in direct contact with experienced Cancer Coaches. Many of the coaches are cancer survivors themselves and understand the physical and emotional challenges that you face.
The role of a cancer coach is to create a lifestyle that you can integrate into your daily life that assists in the treatment, recovery and, in the long term, reduces the chance of cancer recurrence.