Metastatic cancer occurs when cancer spreads from its original site of origin to a distant location in the body. When cancer metastasizes to a different organ, it retains similar features and characteristics of the cancer from the original site. For example, breast cancer may metastasize to the brain, but the metastatic cancer cells will resemble breast, not brain cancer cells.
The process of metastatic growth is complex and requires a series of intricate steps. First, cancer cells grow into healthy tissue surrounding the primary tumor. The tumor cells then travel through nearby lymph nodes and blood vessels into other parts of the body. The tumor cells eventually exit the blood vessels and invade surrounding tissue, where a new tumor begins to form. As the tumor grows at the metastatic site, new blood vessels form, providing blood and nutrients for the new cancer to grow.
Cancer can spread anywhere in the body, but the most common metastatic sites are the brain, bone, liver, and lung. Additionally, each cancer type is associated with different metastatic sites.
Reports indicate that brain metastasis occurs in about 20 – 45% of cancer patients. Some primary cancer sites prone to brain metastasis are breast, kidney, lung, colorectal, and skin cancer. The region of the brain where metastasis occurs is not well understood. However, understanding the unique distribution of metastasis could significantly improve treatment planning and provide more effective therapeutic options for late-stage cancer patients.
A study recently published in the Journal of Neurosurgery made great strides towards correlating the exact location in the brain where metastasis occurs to specific primary cancers. The study examined almost 1,000 patients with brain-metastatic melanoma, kidney, lung, breast, and colorectal cancers.
The researchers performed a procedure called Gamma knife radiosurgery (GKRS). GKRS is a minimally invasive technique often used to treat brain tumors. The specialized approach allows doctors to precisely measure the exact coordinates of a tumor in the brain.
The study showed that lung cancer and melanoma had a high probability of spreading to the frontal and temporal lobes of the brain. Alternatively, breast, renal, and colon cancers more commonly metastasized to the brain's back end, including the cerebellum and brainstem.
Using this data, the research team also developed two distinct predictive mathematical models to estimate the precise location of brain metastases based on the primary tumor site. The first model showed that different parts of the brain were more susceptible to metastatic spread from certain types of cancer. The second model estimated the probability of each cancer type metastasizing to a specific region of the brain. The models gave similar results when evaluating the likelihood of some regions of the brain developing primary cancer-specific metastatic spread.
The authors concluded that their models show that brain metastasis occurs in distinct regions of the brain depending on the original cancer site. They also indicate that the findings of this study could provide a predictive diagnostic tool that would enhance therapeutic strategies to prevent the growth of brain metastasis.