Opioids are important for treating pain in breast cancer, but they may also affect how cancer grows, according to a recent review published in the British Journal of Pharmacology.
Studies done in animals show that some opioids can help tumors grow. At the same time, other opioids, such as tramadol, nalbuphine, and dezocine, may slow tumor growth.
Opioids can also affect the immune system. Some opioids weaken immune cells that help destroy cancer, such as natural killer cells and CD8+ T cells. However, in some situations, drugs like tramadol and buprenorphine may protect or even improve the body’s ability to fight tumors.
Studies in humans have shown mixed results. Around the time of surgery, opioids have sometimes been linked to worse survival and sometimes to better survival, depending on the type of breast cancer. During chemotherapy, there is no strong evidence that opioids make outcomes worse, and some studies suggest tramadol may be linked to better results.
In palliative care, opioids are essential for controlling pain. However, using them for a long time after cancer treatment has been linked to a higher rate of illness and death, so they should be prescribed carefully.
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The review authors said that there is no clear proof that using opioids for cancer pain shortens patients’ lifespan. However, they pointed out that many studies have weaknesses, such as being based on past data and not studying the effects for a long enough period. Scientists also do not fully understand how opioids interact with the tumor and the immune system.
More high-quality research is needed to understand the true effects of opioids on breast cancer, the review authors concluded. “Until such data are available, opioid therapy should be optimized individually, balancing effective pain relief with cautious consideration of potential oncological consequences.”
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