The Importance of Knowing Your Sub-Type

There is important information about every individual person’s cancer that doctors need to know to recommend the most effective treatment.

The type refers to the specific kind of breast tissue that has become cancerous and started to grow uncontrolled. The most common kinds of cancer occur in duct or lobule tissues in the breast. These are known as “ductal carcinoma” or “lobular carcinoma,” respectively.¹

The stage refers to how big the tumor has grown and where the tumor cells have spread in the body, if at all.²

The sub-type refers to specific molecular characteristics of each particular tumor. The sub-type is especially important because different sub-types of tumors are best treated with different drugs.¹

Tumor characteristics

There are two key parameters that help characterize tumors³:

HR: Hormone receptors

• Tumors can be HR+ or HR-.
• Tumors that are HR+ contain molecules that cause the tumor to grow in the presence of the hormones progesterone or estrogen.
• Tumors are considered HR+ when they contain receptors for either of the hormones progesterone or estrogen.
• Tumors that are HR+ can respond to drugs that block the hormones the tumor needs to grow.

HER2: Human epidermal growth factor receptor-2

• Tumors can be HER2+ or HER2-.
• Tumors that are HER2+ contain molecules that cause cancer cells to multiply especially fast.
• HER2+ tumors tend to be more aggressive.

Tumor sub-types and therapies

There are four possible combinations of these two variables. These are called sub-types. Each sub-type responds better to some therapies than to others.³

HR+/HER2-

• The most common form of advanced breast cancer, accounting for 70% of cases.
• The first line of treatment is usually hormone therapy to stop the tumor growth.
• Common hormone therapies include tamoxifen or an aromatase inhibitor.⁴
• Hormone treatments generally work by reducing production of estrogen in the body or blocking estrogen from attaching to the tumor and encouraging its growth.⁵
• HR+ tumors have a lower chance of recurrence, but the tumor can sometimes develop ways to evade therapy.

HR+/HER2+

• This tumor sub-type accounts for 1 out of 5 advanced breast cancer cases.³
• These tumors can respond to hormone therapy, but HER2+ tumors are more aggressive than HER2- tumors.
• A number of medicines are designed specifically to fight HER2+ cancers, mainly by disrupting the cells’ ability to receive growth signals. These include Herceptin, Kadcyla, Nerlynx, Perjeta, Tykerb and Tukysa.⁶

HR-/HER2+

• This tumor subtype does not respond to hormone therapy, since it does not contain a hormone receptor.
• Research shows, however, that HR- tumors often respond better to chemotherapy than HR+ ones.⁷
• This type of cancer is often treated with multiple approaches, including chemotherapy and targeted HER2+ therapies.

HR-/HER2-

• This type of cancer is also known as triple-negative,” since the tumor does not have receptors for estrogen, progesterone, or human epidermal growth factor 2.
• 10-20% of breast cancers are triple-negative.⁸
• This kind of cancer is usually treated with a combination of surgery, radiation therapy, and chemotherapy.⁴
• 70% of people with triple-negative breast cancer also have the mutation BRCA1, which researchers link with breast cancer. It is also more common among African American women.⁸

Therapies that can be effective against triple-negative cancer include⁸:

• Neoadjuvant chemotherapy, which is chemotherapy before surgery
• Poly ADP-ribose polymerase (PARP) inhibitors, which make cancer cells more likely to die
• Immunotherapy medicines like Tecentriq, which enable the immune system to fight the cancer more effectively
• Antibody-drug conjugate like Trodelvy; which is intended to target and kill tumor cells while sparing healthy cells.