Breast cancer is a common cancer that affects women worldwide. When cancerous cells spread to other parts of the body, a process known as metastasis, they can be difficult to eradicate. During metastasis, cells from the cancer spread throughout the body and are likely to be different from the tumor that first occurred. Breast cancer in particular has a tendency to spread to other parts of the body, like the lungs, liver, bones, and brain.
In a healthy body, any cell that detaches from its original location is eliminated. This stops cells from leaving one part of the body and growing in another part, effectively preventing metastasis. However, this process is compromised in cancer cells due to mutations the cancer cells develop.
When a cancer cell metastasizes, it leaves its original location, enters the bloodstream, and travels throughout the body, where it adheres to surrounding tissues. Because the elimination of detached cells is compromised in cancer cells, metastasis can occur rapidly.
Scientists consider many factors when studying cancer treatments, like human toxicity and accessibility of medications. Some researchers are currently looking to aspirin, a common household medication, because it is affordable and safe in controlled amounts. In a recent study, researchers from China and the US hypothesized regular aspirin use could affect the spread of tumors, particularly during breast cancer metastasis.
The scientists designed an experiment to test whether aspirin prevents breast cancer from spreading to the lungs in mice. They injected female mice with breast cancer cells, and allowed the cells to grow in the typical place breast cancer would form. This way, the mice would have breast tumors and the scientists could monitor any metastases of these tumors to the lungs.
They tested five groups of mice that received different treatments for a period of 4 weeks. Two groups of mice ingested aspirin, at a dose of either 100 mg or 200 mg per day. Two groups ingested a drug called indomethacin that is known to slow metastasis, also at a dose of either 100 mg or 200 mg per day. The last group of mice took no medication.
For perspective, a normal dose of aspirin for humans is between 300 to 650 mg of aspirin every 4-6 hours. But the body weight of a mouse is much smaller than the body weight of a human, so these mice were getting relatively high doses compared to what we might take for a headache.
The scientists closely monitored the mice’s body weight throughout the experiment, since changes in body weight can indicate how well the mice are responding to the treatment.
If the mice lost 10% or more of their body weight, the scientists considered this significant weight loss and assumed the drug was harming the mice. But if the mice maintained their body weight, they assumed the mice tolerated the treatment well. The scientists also monitored the survival rate of the mice, the volume of their original tumors, and the number of newly formed tumors during these treatments.
The team found mice treated with aspirin had very similar results to those treated with indomethacin. After the treatment, the scientists detected almost 10 fewer new tumors in the lungs of mice that received aspirin and indomethacin than in the untreated mice.
They also found that about 80% of the mice treated with aspirin survived, while only 50% of the untreated mice survived. Lastly, none of the mice that took aspirin showed significant weight loss, indicating the mice tolerated the treatment well. One limitation to the treatment was that the original tumors did not shrink in the mice given aspirin or in the untreated mice.
The scientists concluded aspirin slowed metastasis in mice, but they noted more research is needed to extend these results to human medicine. They suggested future workers should conduct a clinical trial to test whether aspirin has similar effects on metastasis in humans with breast cancer.