CHEMOTHERAPY : PREREQUISITES
What are the prerequisites before giving chemotherapy?
The drugs used for chemotherapy are a toxic lot, and all of them have some side effect or the other. Some of them can act on the heart muscle and cause a permanent damage, while others may cause disturbances of the peripheral nerves resulting in disturbances in sensation etc. Hence, before a chemotherapy is started, it is essential to ensure the optimal functioning of various organ systems, especially, the heart, the kidney and the liver. The general condition of the patient should be good, else the tolerance of CT will go down and there may be more harms than benefit. Basically, the risk benefit ratio is assessed.
Which tests need to be done before chemotherapy and why?
As mentioned above, a number of tests need to be done to ensure a safe chemotherapy experience. They are as follows:
Complete Blood Count (CBC): A complete bllod count is a must before every chemotherapy cycle. One must see the hemoglobin (must be more than 10gm%, ideally more than 12 is desirable), the WBC count (must be more than 4000/cu.mm), the absolute neutrophil count (ANC) (must be more than 1800), and the platelelt count (must be more than 100000). WBC or the white blood cell count reflects the resistance power of the body. 'Neutrophils' are most important first line defense mechanism of the body. CT should only be given if the WBC and ANC counts are above the desired number. Platelets are important for the first part of clotting of blood, and if the platelets decrease, there is a bleeding tendency. hence this count must also be normal
Renal and Liver Function testThe levels of Serum Creatinine reflect the function of the kidneys. Standard values differ slightly from lab to lab, but on an average, the upper limit of serm creatinine is 1.3mg%. Similarly, the liver function is reflected by the levels of Serum bilirubin (must be less than 1.0mg%), the enzymes SGOT and SGPT, and Prothrombin time. This renal and liver function assessment is important, as majority of chemotherapy agents are metabolised and excreted by the liver or kidney, and if the function is deranged, an adjustment in the dosage of the chemotherapy agent will be needed.
ECG and 2D Echocardiogram with Doppler studiesThese tests give an idea of the function of the heart, both structural as well as functional. Common drugs like Doxorubicin and Epirubicin have a definite effect on the heart as well, and before giving these drugs, we have to ensure a normal heart function. If the heart function is deranged, we might have to consider giving other chemotherapy agents.
How often is chemotherapy given
Most chemotherapy regimens are given for 6 cycles, with a gap of 21 days between each cycle. For example, combination of Cyclophosphamide, Epirubicin and 5 Fluorouracil or the FEC regimen, as it is called, is given for 6 cycles with gaps of 21 days between each cycle. Some agents like Taxanes are given in both three weekly forms, as well as weekly cycles. So the number of cycles will depend on the combination of drugs used.
Also important to mention here is that, before every cycle, a complete blood count is a must. And if the counts are not above the minimum permissible, then we may have to wait for a few more days or even a week for the counts to be normal, before giving the next cycle of chemotherapy.
What are the routes to administer chemotherapy?
Chemotherapy is to be delivered into the veins. This can be achieved by the following ways:
Peripheral Venous Access In this, the vein of the hand of the non operated side is cannulated by an 'intracath', and the chemotherapy agents are administered, very similar to how a normal saline is administered.
Central Venous Access This is commonly referred to as 'PORT'. A small container, abount the size of a coin, and about a centimetre thick, attached to a long catheter, is implanted onto the chest, below the collar bone, and that tube is tunneled below the skin and inserted into a large central vein, wither in the lower neck (Internal Jugular Vein), or below the ollar bone (Subclavian Vein). So the container is bang below the skin, and the tube is in the vein. Special right angled, winged needles are available, which are inserted into the container and drugs are delivered. This is the system of choice, is very convenient for the patient, who already has undergone so many pricks for tests and so on, and wherever possible and feasible, must be used.