Drug Delivery Methods and Therapies for Cancer Treatment
08 Sep 2016
Cancer is a widely known disease involving abnormal and uncontrolled cell proliferation resulting in solid tumor development or blood cancer conditions. Therefore, when it comes to fighting cancer, the aim is to kill the cancerous cells and/or inhibit the uncontrolled proliferation.
Most common treatment options involve surgeries to remove the tumor, radiation therapy, and chemotherapy. While surgery typically aims at removing the tumor, it is commonly followed by radiation or chemotherapy to kill any of the remaining cancer cells. The two latter processes can be used as a post-surgical treatment or as the direct treatment option depending upon the nature of the disease.
- Radiation therapy involves direct incidence of high energy particles such as gamma rays to damage the cancer cells.
- Chemotherapy is the systemic administration of small molecule drugs, which either directly kill the cells or trigger specific cell-signaling pathways indirectly leading to cell death and/or inhibiting proliferation.
Focusing on the chemotherapy based treatment, anticancer drugs are most commonly classified as (A) Classic cytotoxic drugs, which directly attacks the tumor cells. These are further classified as:
- Non-specific, which end up killing normal cells along with the cancerous cells and tumor tissue
- Targeted drugs, which specifically bind to the tumor cells and kill them minimizing the damage to the healthy cells
Another class of chemotherapy drugs is (B) Modifier drugs. These drugs modify the cell metabolism to slow down the tumor progression and cell differentiation resulting in the cell death. Modifier drugs are further divided into sub-categories depending on which metabolic step the drug is going to interrupt:
- Cell biological modifiers
- Biological response modifiers
- Biochemical modulators
For example, Bevacizumab by Genentech is an angiogenesis inhibitor, which comes under the category of biological response modifiers. This drug inhibits a stimulator for angiogenesis and has been widely used to treat metastatic colorectal cancer . Given the mechanism of action, modifier drugs are relatively more specific to cancerous population compared to the cytotoxic drugs.
Anticancer drugs can either be administered in the form of oral pills or as an injectable (parenteral form).
- Parenteral drug administration is generally referred to as the non-oral route of administration, most commonly through injections or infusion. They can go as intravenous (IV), intraperitoneal (IP), intramuscular, or subcutaneous. This form of administration is conventionally preferred in chemotherapy because parenteral routes bypass the absorption step (as in the case of oral forms), administrating drugs directly into the blood stream for accelerated action.
- Oral drug administration is convenient for the patient since they do not have to make multiple hospital visits for IV-based chemotherapy. Since orals go through various systemic absorption steps, they can circulate in the body for a longer time. Therefore, orals are advantageous for protracted treatment compared to the parenteral form, which is eliminated from the body relatively quickly.
Oral administration, however, suffers from many setbacks. Oral intake can result in nausea and vomiting, resulting in insufficient drug absorption and incomplete treatment. Another very important behavioral factor is the adherence to the schedule. Not following the prescription schedule may result in errors, risk of toxicity or over dose, and pose barriers to proper chemo treatment therapies. These issues can be avoided with parenteral, which are given under clinical supervision with proper drug administration records.
Certain types of cancer require parenteral use out of necessity. Bladder cancer, for example, requires the drug to be given through a urinary catheter that is inserted into the bladder in high concentrations. Also, for infant and pediatric patients, IV can be an easier way to complete the dose than oral since they are not required to swallow anything.
The diagram below shows different options that can be considered when combining the various drug types and administration routes previously mentioned.
A major concern for cancer patients is the sterility of parenteral-based chemotherapy. Since the drug is administered directly into the bloodstream, it bypasses the body’s natural defense system. Any contamination can have serious adverse effects on patients who are already physiologically fragile and more likely to succumb to external stress. This criteria becomes more pressing with leukemia patients, who are more prone to catch infections from the environment and can become worse with bacterial/fungal/viral contamination directly in the blood stream. Therefore sterility becomes a high priority factor while parenteral manufacturing.
To learn more about the sterile manufacturing and development of parenteral drugs, visit our website at coldstreamlabs.com.
 Xiong-Zhi Wu, A new classification system of anticancer drugs-Based on cell biological mechanisms, Medical Hypotheses, 66 (2206), p 883-887