The Traditionally used Standard Maximum Tolerated Dose chemotherapy is known to have many toxic side effects and can cause chemoresistance. Because of these problems, we are now using "metronomic low-dose chemotherapy." A new study from 2019 showed that high dose chemo could cause cancer metastasis. An international team of sciences led by Michelle De Palma, a researcher from the Institute for experimental cancer research, found that high dose chemotherapy causes tumor cells to secrete small vesicles called exosomes. The exosomes have a protein called annexin, which facilitates the survival, spread, and growth of the cancer cells. In 2018 as reported in the International Journal of molecular sciences, "chemotherapy exacerbated breast cancer metastasis." Despite reducing the size of the primary tumor, chemotherapy changes to tumor "microenvironment," resulting in an increased escape of cancer cells into the bloodstream. "The chemotherapeutic drugs exert selective pressure that allowed resistant cancer cells to survive, grow, and eventually thrive."

We now know that angiogenesis with the growth of new blood vessels is a crucial factor in the metastatic growth of Cancer. The good news is with low dose chemotherapy there is inhibition of new blood vessel growth. We are targeting both the blood vessel cells and the tumor cells, which are in a proliferating stage. New studies have also shown that low-dose chemotherapy can ameliorate the rise in circulating cancer cells, causing metastasis, as seen with conventional chemotherapy.

The main characteristics of metronomic low-dose chemotherapy are that administration is frequent without lengthy interruptions. The good news is that there is a low incidence of treatment-related toxicity. Due to the routine administration, there are not rising and falling plasma levels, such as in conventional chemotherapy. Another important distinction that is well known is the high dose of chemotherapy's adverse side effects to the immune system, such as a lowering of your white blood cells and platelet count as well as hemoglobin. This side effect rarely has been seen with low-dose chemotherapy. Also, low-dose chemotherapy has shown to lower the number of T regulatory cells, which improves our immunity and does not suppress it as in conventional treatments.

With the addition of new molecular biologic evaluation, we can now target each patient's therapy. There is now individualization and personalization of chemotherapy, which is truly personalized medicine. We have now treated across the world different tumor types.