Which treatments cause hair loss

Several treatments for breast cancer can cause hair loss or thinning of hair. For many people, this is one of the worst parts of treatment. You may need help to cope with hair loss.

The drugs most likely to cause hair loss are:

• chemotherapy
• hormone-blocking therapies
• some targeted therapies.

Some treatments may have no effect on your hair, and others may thin your hair, but not cause it to fall out completely.
Your medical oncologist can tell you how your treatment might affect your hair.

Chemotherapy and hair loss

Chemotherapy can have the biggest impact on hair loss of all treatments, but not all chemotherapy drugs cause hair loss.
Hair usually starts to fall out about 2 to 3 weeks after the first chemotherapy treatment.

If you plan to cover your head, it can be helpful to arrange this before your hair starts to fall out.

Once hair loss starts, it generally happens quickly – from a couple of days to a little longer than a week.

The first thing you may notice is that your scalp becomes sore or itchy. It may be uncomfortable to rest your head on a pillow.

You may find that your hair starts to fall out when you wash it. Hairs may be on the pillow when you wake up. Brushing or running your fingers through your hair may cause it to come out in clumps.

With some chemotherapy drugs, you are likely to have hair loss in other places, such as:

• eyebrows and eyelashes
• arms and legs
• underarms
• pubic area
• nasal hair
• chest hair, in men.

The good news is that hair loss from chemotherapy is usually only temporary. The time varies from person to person, but your hair will grow back.

About 6 weeks after your final treatment, you will have a short but thick covering of hair over your whole scalp.

Sometimes hair grows back a different colour or texture. It may even be curly when it used to be straight.

Body hair also grows back.

Occasionally this regrowth will start before you finish treatment. This does not mean the treatment is less effective.
Long-term or permanent hair loss has only been reported in a very small number of cases.

Hormone-blocking therapy and hair loss

Some hormone-blocking medications have a side effect of hair loss or hair thinning. These include:

• tamoxifen
• Fulvestrant (Faslodex)
• Aromatase inhibitors such as anastrozole (Arimidex), exemestane (Aromasin) and letrozole (Femara)

Any hair loss probably won’t be obvious until 6 months to 2 years after you start the medication. The amount of hair loss may level off after about a year but will last as long as you are on the treatment.

Hair usually begins to grow back a few months after you stop treatment.

Targeted therapy and hair loss

Some targeted therapies for breast cancer can cause mild hair loss or change the texture of your hair. These include:

• CDK4/6 inhibitors - ribociclib (Kisqali), palbociclib (Ibrance), abemaciclib (Verzenio)
• Trastuzumab emtansine (TDM1 - Kadcyla)
• Trastuzumab deruxtecan (TDXD - Enhertu)
• Sactizumab Govitecan (Trodelvy)

Any hair loss usually starts a few weeks after you start the medication. Hair begins to grow back several months after you finish the therapy or sometimes even during treatment. The risk of hair loss is higher if you are taking an aromatase inhibitor such as anastrozole (Arimidex) or letrozole (Femara) at the same time.

Radiotherapy and hair loss

Like chemotherapy, radiotherapy affects healthy cells as well as cancer cells. It can cause hair loss, but only in the specific area being treated. For example:

• Radiotherapy to the lymph nodes in your armpit and your breast means you’ll lose underarm hair in the area treated.
• Men who have radiotherapy may lose hair from the part of their chest that is treated.
• Radiotherapy for brain metastases may cause hair loss. Stereotactic radiotherapy will only affect the areas targeted; with whole brain radiotherapy, people usually lose all hair from their head.

How much hair you lose depends on the dose and exact site of the radiotherapy treatment. Hair may be patchier or thinner when it grows back.

Your radiation oncologist or nurse will talk to you about the likelihood you may lose your hair before treatment begins.