How Fast Does Breast Cancer Grow and Spread?

Breast cancer growth varies widely, but it generally takes years to develop before detection, often starting as a mutation in a single cell. Understanding factors like subtype and growth rate can guide treatment decisions and help manage concerns about tumor progression.

What Does Doubling Time Mean for Breast Cancer?

People often want to know how fast a breast tumor will double so they can decide when to start treatment. Understanding this growth rate is also important if you’ve been advised to observe a lump over time.

The growth rate of breast cancer can vary, but studies offer estimates.

Breast Cancer Cell Growth

Cancer begins with genetic changes, known as mutations, in a normal breast cell. These mutations affect genes that control cell growth and can occur over decades before forming a cancer cell.

Tumor cells then multiply and divide exponentially, with one cell becoming two, two cells becoming four, and so forth. As the tumor grows larger, its size increases more rapidly.

However, not all cancer cells are dividing at the same time. The growth rate can vary during different tumor stages. Breast cancer, in comparison to many other cancers, has a “low growth fraction,” meaning a smaller proportion of cancer cells are actively dividing.

Other cancers, like lymphomas and certain leukemias, have higher growth fractions and may become active and detectable more quickly, even in children.

Breast Cancer Doubling Time

To understand how quickly breast cancer grows, researchers use “volume doubling time,” which measures how long it takes for a tumor to double in size.

In a 2018 study, researchers used a series of ultrasounds on 265 people with invasive breast cancer. They found growth rates varied significantly by tumor subtype and estrogen receptor status.

Over 57 days, 36% of tumors remained the same size, while 64% increased, with an average volume gain of 34.5%. Triple-negative tumors grew faster with shorter doubling times compared to estrogen receptor-positive and HER2-negative tumors.

A 2016 study followed 323 people, using ultrasound images between diagnosis and surgery over 31 days. Tumors grew from 1.47 to 1.56 centimeters on average. The daily growth rates for different tumor types were:

• 1.003% per day for triple-negative tumors
• 0.859% per day for HER2 positive/estrogen receptor-negative tumors
• 0.208% per day for estrogen receptor-positive tumors

Which Variables Impact Breast Cancer Growth?

Several studies have identified other factors that affect breast cancer growth rates, including:

• Type of cancer: Inflammatory breast cancer generally grows faster than other types.
• Age at diagnosis: Breast cancer in younger women tends to grow faster and have a higher tumor grade compared to older women.
• Menopausal status: Tumors may grow more rapidly in premenopausal women, likely due to higher estrogen levels in the body.
• Receptor status: Triple-negative cancers typically grow faster than estrogen receptor-positive tumors, as do triple-positive tumors.
• Estrogen treatment: Women who have used hormone replacement therapy after menopause often experience faster tumor growth rates.
• Ki-67 index: This measures a tumor marker. A higher index indicates a faster doubling time.
• Tumor grade: This describes the appearance of the cells. A higher grade indicates a faster doubling time.

When and How Does Breast Cancer Spread?

Metastasis, the spread of breast cancer to other parts of the body, is responsible for most breast cancer deaths. This makes it important to know how fast breast cancer spreads.

Breast cancer usually spreads first to the lymph nodes from under the arm. This is called lymph node-positive breast cancer. It’s considered early-stage and is potentially curable even if lymph nodes are involved.

When cancer spreads to parts of the body like the bones, brain, lungs, or liver, it becomes stage IV or metastatic breast cancer, which is no longer curable.

Most breast cancers have the potential to spread. Carcinoma in situ or stage 0 breast cancer is considered non-invasive because of its limited spread. It is potentially 100% curable with surgery.

All other stages of breast cancer (stage I to stage IV) are considered invasive and have the potential to spread. Spread to lymph nodes, even when in the early stage, is very important because it indicates the cancer’s potential to spread beyond the breasts.

Why Do Some Breast Cancers Spread Faster?

Certain types and subtypes of breast cancer spread more easily and earlier than others. Ductal carcinoma, for example, is more likely to spread than lobular carcinoma in tumors of the same size and stage.

Many breast cancers do not spread to lymph nodes until the tumor is at least 2 cm to 3 cm in diameter. Some types may spread very early, even when a tumor is less than 1 cm in size.

Tumor Size and Spread to Lymph Nodes

There is little evidence to link tumor size and lymph node spread for very small and very large breast tumors. For tumors in the range most commonly seen clinically, the tumor size correlates with the risk of lymph nodes being involved.

How Does Breast Cancer Develop Over Time?

The time it takes for breast cancer to grow from a single cell to a tumor is unknown. This is because doubling time estimates assume a constant rate of growth.

If this were true, cancer with a doubling time of 200 days would take 20 years to develop into a detectable tumor. A doubling time of 100 days would take 10 years to be found on exam. In contrast, a breast tumor with a doubling time of 20 days would take only two years to develop.

Most studies have found the average doubling time to be between 50 days and 200 days. This means it’s possible that breast cancers diagnosed now began at least five years earlier, but again, this assumes the growth rate is constant, and it is not.

How Early Can Breast Cancer Be Found?

The earlier a breast cancer is found, the greater the chance it can be cured. This is what makes routine mammogram screening and self-breast exams so important.

Breast Examination

Self-breast exams allow people to learn how their breasts typically look and feel. Some people—especially those at an increased risk for breast cancer—may find self-exams helpful and empowering.

Experts don’t all agree about the benefits of breast self-exams. The American Cancer Society (ASC) does not specifically recommend regular provider breast exams or breast self-exams since there is a lack of evidence that they help diagnose breast cancer early.

However, the ACS says it is important for a woman to “be familiar with how their breasts normally look and feel and should report any changes to a health care provider right away.”

If a woman finds a lump, they should contact their doctor immediately, even after a recent normal mammogram.

Mammogram

Breast cancers are sometimes detected when very small by the presence of microcalcifications in the breast. (These small calcium deposits may be an early sign of cancer.) The average size of a tumor found by mammogram is 1.1 cm. The earliest a tumor may be found on a mammogram is between 0.2 cm and 0.3 cm in diameter.

Researchers have looked at how effective mammograms are in finding breast cancer. Some believe that a rise in women having mammograms from the 1980s onward is associated with trends in the average size of tumors at the time of breast cancer diagnosis.

From 1984 to 2014, the average size of breast cancer at diagnosis decreased by 26%, from 2.6 cm to 2.0 cm. However, a different study looked at the size of breast tumors at diagnosis from 2001 and 2014. It found that, unlike earlier, the size of breast tumors increased by 3% to 13%.

Breast MRI

So far, there is little data to describe the average or smallest size of a breast tumor that breast MRI can find. It may be a more sensitive and valuable tool for women with a family history of familial breast cancer.

A newer technique called “fast MRI” may offer a higher detection rate than mammograms alone for people of average risk, especially women with dense breast tissue.