The visual of someone undergoing cancer treatment often includes a shaved head, leading many to believe that hair loss is an unavoidable part of a cancer diagnosis. However, this common association is largely a side effect of certain treatments, not the cancer itself. Hair loss, or alopecia, is a potential outcome of therapies designed to target rapidly dividing cells, which can inadvertently affect healthy cells, including those responsible for hair growth.
Chemotherapy’s Impact on Hair Follicles
Chemotherapy drugs target rapidly dividing cells, a characteristic of cancer. However, this targeting cannot differentiate between cancerous cells and other healthy, rapidly dividing cells, like those in hair follicles. Hair follicles are highly active structures with many cells in constant growth, making them particularly susceptible to chemotherapy.
Chemotherapy drugs disrupt cell division in hair follicle cells, leading to weakening and shedding of hair. Hair loss can occur on the scalp and other body parts, including eyelashes, eyebrows, armpits, and pubic hair. The extent and timing of hair loss, known as chemotherapy-induced alopecia (CIA), depend on the specific drugs, their dosage, and the treatment schedule.
Hair loss typically begins within one to three weeks after starting chemotherapy. Patients may notice hair falling out in clumps, or it may thin gradually. The first areas to show loss are often those that experience more friction, such as the sides and back of the head. By approximately three months into treatment, hair loss is often complete.
Other Cancer Treatments and Hair Loss
While chemotherapy is most commonly associated with widespread hair loss, other cancer treatments can also affect hair. Radiation therapy, for instance, causes hair loss only in the specific area of the body being treated. If radiation is directed at the head or neck, hair loss on the scalp or face may occur.
The hair loss from radiation therapy is localized because the high-energy beams target cancer cells within a defined field, and only hair follicles within that field are affected. The severity and permanence of hair loss depend on the radiation dose, with higher doses increasing the likelihood of permanent hair loss. Hair in the treated area may begin to fall out within two to three weeks of starting radiation therapy.
Targeted therapies focus on specific molecules involved in cancer growth. Some targeted therapies can cause hair thinning, make hair dry and brittle, or even lead to changes in hair texture, such as becoming curly. Complete hair loss is less common with targeted therapies than with chemotherapy, but it can occur with long-term use of certain drugs, such as epidermal growth factor receptor (EGFR) inhibitors.
Immunotherapy, which boosts the body’s own immune system to fight cancer, generally has a lower incidence of hair loss compared to chemotherapy. While hair thinning or partial hair loss can occur, it is less common for immunotherapy to cause total hair loss. The onset of hair changes with targeted therapies and immunotherapy may also be slower and take longer to recover from than with chemotherapy.
Hair Regrowth After Treatment
For most individuals, hair loss experienced during cancer treatment, particularly from chemotherapy, is temporary. Hair regrowth typically begins once treatment concludes, as the body starts to recover from the effects of the medications. Patients may observe the first signs of new hair growth, often described as a soft fuzz, within three to six weeks after their last chemotherapy session.
Within two to three months after treatment, a short covering of hair is usually visible, and by six months, many individuals have about an inch or more of hair growth. It can take up to 6 to 12 months for hair to return to a fuller state and regain its pre-treatment length and thickness. The new hair might initially have a different texture, color, or thickness than before treatment.
For example, hair that was once straight may grow back curly, a phenomenon sometimes referred to as “chemo curls”. The color might also appear lighter or darker, or even grey, until the pigment-producing cells fully recover. These changes in texture and color are usually temporary, with hair gradually returning to its original characteristics as the hair follicles continue to heal and normalize their function.
Dispelling Common Misconceptions
A common misconception is that all cancer patients will lose their hair. Hair loss is a side effect of certain cancer treatments, primarily chemotherapy and localized radiation therapy, and not a direct symptom of the cancer itself or its severity. Not all chemotherapy drugs cause hair loss, and some may only lead to mild thinning.
Hair loss does not indicate the effectiveness of the treatment or the stage of the disease. Instead, it reflects how certain medications interact with the body’s rapidly dividing cells, including healthy hair follicle cells. Many cancer treatments, such as certain targeted therapies, immunotherapies, and hormonal therapies, are less likely to cause significant hair loss or may only result in hair thinning.