Brain metastases happen when cancer begins elsewhere in the body and spreads metastasizes to the brain. Brain metastases occur when cancer cells spread from their original site to the brain. Any cancer can spread to the brain, but the types most likely to cause brain metastases are lung, breast, colon, kidney and melanoma. Brain metastases may form one tumor or many tumors in the brain. As the metastatic brain tumors grow, they create pressure on and change the function of surrounding brain tissue.
"Chemo brain" not linked to breast cancer drug, study finds
"Chemo brain" not linked to breast cancer drugs, anthracycline chemotherapy, study finds - CBS News
Post-chemotherapy cognitive impairment PCCI also known in the scientific community as " CRCIs or Chemotherapy-Related Cognitive Impairments " and in lay terms as chemotherapy-induced cognitive dysfunction or impairment , chemo brain , or chemo fog describes the cognitive impairment that can result from chemotherapy treatment. The phenomenon first came to light because of the large number of breast cancer survivors who complained of changes in memory, fluency, and other cognitive abilities that impeded their ability to function as they had pre-chemotherapy. Although the causes and existence of post-chemotherapy cognitive impairment have been a subject of debate, recent studies have confirmed that post-chemotherapy cognitive impairment is a real, measurable side effect of chemotherapy that appears in some patients. PCCI is often seen in patients treated for breast cancer , ovarian cancer , prostate cancer , and other reproductive cancers,  as well as other types of cancers requiring aggressive treatment with chemotherapy. The clinical relevance of PCCI is significant, considering the increasing number of long-term cancer survivors in the population, many of whom may have been treated with aggressive dosing of chemotherapeutic agents, or with chemotherapy as an adjuvant to other forms of treatment.
Chemotherapy for Breast Cancer
Sometimes people with cancer worry about, joke about, or become frustrated by what they describe as mental cloudiness or changes they might notice before, during, and after cancer treatment. This cloudiness or mental change is commonly referred to as chemo brain. Doctors and researchers may call chemo brain many things, such as cancer treatment-related cognitive impairment , cancer-related cognitive change , or post-chemotherapy cognitive impairment. The word "cognitive" refers to the way your brain works to help you communicate, think, learn, solve problems, and remember.
These problems were first reported after chemotherapy treatment. For example, researchers first looked at this in women with breast cancer and found that chemotherapy might be the cause. Another name people use is chemo fog.