Researchers have identified another potential therapy for early-stage breast cancer.
Radionuclide therapy is a systemic (or whole-body) treatment that travels through the body via the bloodstream, like chemotherapy does. However, the radioactive substances in the treatment target diseased cells in particular, so side effects are greatly reduced (unlike chemotherapy).
Roughly 20% of five-year breast cancer survivors will experience metastatic breast cancer sometime within five to ten years after treatment for the first occurrence of breast cancer. Metastatic breast cancer occurs when cancerous cells from the initial tumor break off and gain access to the circulatory system. From there, they can travel anywhere in the body. These cancerous cells are called disseminated tumor cells (DTCs). DTCs may immediately develop into tumors elsewhere in the body, or they may stay dormant for several years before suddenly becoming active.
Researchers have found that radionuclide therapy can accurately target these DTCs and delay or stop their growth in early-stage breast cancer. Radionuclide therapy utilizes the alpha-particle-emitting radiopharmaceutical 223RaCl2 (Radium-233 dichloride). Not only can the treatment target DTCs, but it also is able to find and attack cancer cells that are outside of the immediate radiation field, called bystander cells.
The study was published in the Journal of Nuclear Medicine. Researchers split female mice into three groups. First, each group was given either 0 kBq/kg (the control group), 50kBq/kg, or 600 kBq/kg of 223RaCl2 to create bystander conditions. Then, 24 hours later, the bone marrow of the mice were injected with human breast cancer cells that were either estrogen receptor-positive (ER+) or triple negative (which is not fueled by estrogen, progesterone, or HER2). The tumor cell count was measured on day one and then once a week after that to track growth.
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Researchers found that DTCs were present in mice with both types of breast cancer. They found that mice with ER+ breast cancer had a 7-day growth delay in tumor progression when given 50 kBq/kg of 223RaCl2, and a 65-day growth delay when given 600 kBq/kg. The mice with triple negative breast cancer (TNBC) experienced a 10-day growth delay in tumor progression when given 600 kBq/kg. The mice with TNBC who were given 50 kBq/kg experienced no significant difference from the control group.
“The increased magnitude of the bystander effect in this study suggests that higher injected activities may better sterilize undetected dormant or slow-growing DTCs in the bone marrow micro-environment,” said researchers.
Because of these promising results, researchers say it may eventually be an option for certain patients who are in the early stages of breast cancer.
“This study adds to the mounting evidence that radiation-induced bystander effects can play a role in in the design of future treatment plans for radiopharmaceuticals alone or combined with external-beam therapy,” researchers said. “Furthermore, the capacity to target specific cells or tissues in a systemic manner may offer advantages over the use of external beams of radiation for eliciting therapeutic bystander responses.”Whizzco