How Fast Does Breast Cancer Start, Grow, and Spread?

People with a breast cancer diagnosis often wonder how long ago the cancer started. The answers vary based on your genetic makeup, the type of cancer, and how far it has advanced.

Some experts suggest that it's likely that many tumors begin a minimum of five years before they are detected.

This article looks at the factors that can affect the growth rate of cancer and how long it takes breast cancer tumors to develop. It also explains why the answers are essential for people living with breast cancer today.

How Fast Breast Cancer Grows

One main reason people ask about how fast breast cancer grows, or its doubling time, is when they consider how long to wait to begin treatment. This growth rate is also important to understand if you have a lump and have been advised to simply observe it over time.

In general, the growth of breast cancer can be quite variable, but several studies provide at least an estimate of what may be happening.

Breast Cancer Cell Growth

Cancer begins when genetic changes, called mutations, occur in a normal breast cell. These changes happen in genes that control the growth of the cell. These changes may occur over a long period, even decades, before a cancer cell forms.

These tumor cells multiply and divide exponentially, meaning that one cell becomes two, two cells become four, and so on. That's why a tumor's size will increase more rapidly the larger it becomes.

That said, not all cells are dividing at the same time. Cancer's growth can change at different stages as a tumor forms. Compared with many types of cancer, breast cancer has a "low growth fraction." This means the proportion of cancer cells in an active cell cycle is low.

Some tumors, such as lymphomas and some leukemias, have much higher growth fractions. They may be active for a much shorter period before they are detected, even in children.

Breast Cancer Doubling Time

A meaningful way to think about how fast breast cancer grows is by looking at the volume doubling time. The growth rate is a part of tumor doubling time, which is precisely what it sounds like. It is the time it takes for a tumor to double in size.

A 2018 study estimated doubling time by looking at serial ultrasounds in 265 people with invasive breast cancer to see if there were differences among breast cancer subtypes. These images were taken between diagnosis and surgery. The results suggest that growth varied significantly based on the breast cancer subtype and the role of estrogen receptors in those subtypes.

During an average interval of 57 days, 36% of tumors did not change in size, while 64% grew. Of those tumors that increased in size, the average gain in volume was 34.5%. Tumors that were triple negative had more significant increases in volume and shorter doubling times than those that were estrogen receptor-positive and HER2-negative tumors.

A similar 2016 study looked at growth in 323 people, based on ultrasound images taken between diagnosis and surgery over 31 days, On average, the tumors grew from 1.47 centimeters (cm) to 1.56 cm in diameter. The daily growth rate based on type was:

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

Factors That Affect Growth Rate

Several studies have identified other factors that affect the growth rate of breast cancer. These include:

• The type of cancer: Inflammatory breast cancer tends to grow much more quickly than other types of breast cancer.
• Age at diagnosis: Breast cancers in young women tend to grow more rapidly than breast cancers in older women. They also have a higher tumor grade.
• Menopausal state: Breast tumors often grow more rapidly in women before menopause than in postmenopausal women. This is likely due to estrogen in the body.
• Receptor status: Triple-negative cancers, in general, grow more rapidly than estrogen receptor-positive tumors. Triple-positive tumors also grow more rapidly.
• Estrogen treatment: Women who used hormone replacement therapy after menopause had, in general, a more rapid growth rate of breast tumors.
• Ki-67 index: This measures a specific tumor marker. A higher index means a faster doubling time.
• Tumor grade: This describes what the cells look like. A higher tumor grade indicates a faster doubling time.

How Quickly Breast Cancer Spreads

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 lymph nodes under the arm. This is called lymph node-positive breast cancer. Breast cancer is considered early-stage and potentially curable even with the involvement of lymph nodes.

When cancer spreads to regions such as the bones, brain, lungs, or liver, it is considered stage IV or metastatic breast cancer. This means it 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.

Factors Associated With More Rapid Spread

Some types of breast cancer, as well as their subtypes, are more likely to spread (and spread earlier) than other types. For example, ductal carcinoma is more likely to spread than lobular carcinoma among 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 Quickly Breast Cancer Develops

The actual time it takes for breast cancer to grow from a single cancer cell to a cancerous tumor is unknown. Part of the reason is that estimates based on doubling time assume that the rate stays constant at all times as the tumor grows.

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. It is not.

When Can Breast Cancer First Be Detected?

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.

Summary

The growth rate of cancer cells determines how fast a breast cancer grows. It also relies on "doubling time" models to estimate that growth. The subtype of breast cancer is a primary factor in its growth. Other factors include the Ki-67 tumor marker level and the tumor grade, which involves the physical characteristics of cancer cells when seen under a microscope in the lab.

How quickly cancer grows can vary, but early detection may lead to better outcomes. Be sure to contact your healthcare provider for routine mammogram screening and exams that may help to find breast cancer in its earliest and most treatable stages.