| Ch 9 | Page 21 / 34 | |
| Cancer chemotherapy |
Haematological toxicity | |
Cancer chemotherapy has numerous toxicities which can be classified in two major categories:
- acute toxicities, the great majority of which are common to many chemotherapy drugs,
- chronic toxicity, which, conversely, is often specific to one therapeutic family.
Normal erythropoieis is the permanent, finely regulated production of red blood cells. Anaemia is commonly observed during malignancy without any connection to treatment. The mechanisms of this anaemia are diverse.
Most chemotherapies will eventually induce anaemia, generally of a normocytic type, sometimes macrocytic (for instance cisplatin), the correction of which can necessitate transfusions, particularly when anaemia becomes symptomatic (dyspnea, fatigue), which usually occurs when the haemoglobin level is lower than 8 g/dl.
Patients receiving aplastic chemotherapy, should be set on specific transfusion programs (in order to reduce the production of antibodies against irregular blood groups).
In reality, this very classical attitude is currently undergoing complete change thanks to the large use of erythropoietin. This hormone has become a genuine drug which should be prescribed when the haemoglobin level falls below 10 g / dl. This treatment avoids multiple transfusions, reduces respiratory disorders and alleviates the fatigue generally experienced by patients.
Some anticancer drugs are more severely toxic on platelets (dacarbazine, carboplatin). In general, after chemotherapy, the day that thrombocytopenia nadir will occur is well known, thus blood counts should be regularly performed in order to identify precisely when the patient will need to be transfused.
Simply speaking, over 50,000 platelets, there is no significant risk of haemorrhage (except in particular circumstances) and monitoring is sufficient.
Down to 20,000 platelets, among young and calm patients, rest and elementary precautions are sufficient to avoid any significant bleeding.
Below 20,000 (particularly among fragile patients), hospitalisation should be proposed in order to perform platelet transfusions after research for immunisation against HLA antibodies. Platelet concentrates, when the donor has the same blood group as the patient and the closest possible HLA group, induce a rapid increase in the platelet count; however this increase remains stable for a very short period (less than 48 hours) except when the patient's bone marrow takes over.
This attitude is very different to the one we adopt when faced with thrombocytopenia provoked by progressive medullar insufficiency (for instance due to marrow invasion by prostate cancer cells or breast cancer cells). Unfortunately, platelet transfusions are difficult to justify if no cancer treatment is available: in fact, it is just like a pierced barrel since the mean lifespan of transfused platelets is around 24 to 48 hours.
Platelets should only be transfused for acute thrombocytopenia.
We are still patiently awaiting the results of clinical studies validating a platelet growth factor.
Leukopenia is not in itself a major problem if it is of short duration. Any possible external or internal contamination should be avoided (visits, children, cleanliness and so on). There is no point in systematically instituting prophylactic antibiotherapy. (The opposite applies to very strong chemotherapies which require bone marrow graft or produce very long aplasia).
Conversely, the appearance of fever constitutes an emergency. It should generate the rapid verification of the white blood count and if leukopenia is confirmed, vigorous treatment should be instituted (possibly requiring rapid hospitalisation in order to avoid potentially lethal septic shocks). Some authors treat all cases of leukopenia (even with fever) at home if they last no longer than one or two days.
A chemotherapy protocol should precisely describe follow-up and in particular the days of the cycle on which white blood cell counts will probably fall to a nadir. On these specific days, precise haematological monitoring may be prescribed if necessary. This monitoring should be conducted by the physician prescribing the chemotherapy. Outwith this nadir period (and the day of prescription), blood counts are totally pointless.
Growth factors have brought significant progress in the treatment of leukopenia. Their indications are, however, much wider than the sole prevention of leukopenia.
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