Our experience in the Imuran treatment of acute leukemia is rather scarce. Indeed because of the difficulty to get this drug, we could use it in 6 cases only. These 6 cases belonged to the following forms: 3 to the stem cells type, 1 to the myelomonocytic type, 1 to the histiomonocytic ungranulated type, 1 to the promyelocytic type (acute terminal crisis of chronic myeloid leukemia). All these patients had been already treated with other antiblastics.

Positive results we had just in 2 cases, precisely in a case of stem cells leukemia and in the last case above mentioned. Similar results in acute relapsing phase of chronic myeloid leukemia obtained Eridani et al. (1965). Where we applied strong doses (mg 30c of Imuran daily for 10 days), following the advice of Storti and Traldi (1965), and thus obtained a full three months remission (Fig. 1).

According to this modest experience of ours Azathioprine is a drug that does not present clear advantages on 6-Mercaptopurin.

The report presents the clinical results of treatment with Azathioprine 6 [(methyl-4-nitro-5-imidazolyl) thio] purine, in patients with acute leukaemia, the acute relapsing phase of chronic myelocytic leukaemia and in a group of patients affected by illness which have probably an autoimmune pathogenesis.

Favorable results were obtained in the group of patients suffering from acute leukaemia with a percentage of clinical and/or haematological remission of 57%.

A comparative analysis of the length of survival in these patients compared to that of a similar group of patients treated with 6-mercaptopurine is also reported.

A fair response was also obtained in the group of patients in the acute relapsing phase of C.M.L.

In the group of patients affected by diseases probably due to an immune pathogenesis, a favorable response was obtained in 2 cases of systemic lupus erithematosus with haemolytic anaemia and 1 case of acquired autoimmune haemolytic anaemia.

1. Lists have been made of the more frequently occurring malignant diseases and of those commonly available oncolytic drugs which, in the author's opinion, are most appropriate for their treatment.

2. Those tumors which do not usually respond to oncolytic drugs have also been listed.

3. For several malignant diseases it has been found that small doses of oncolytic drugs have proved just as effective for inducing remission and even more effective in prolonging remission than have larger doses of these drugs. The explanation for this may be that smaller doses do less harm to the body's immune defense mechanism than do larger doses.

Antimitotic drugs essentially induce a direct inhibition on the malignant cellular proliferation. Secondary mechanisms should even be considered: i.e. neoplastic clonal disadvantage, indirect antivitaminic mechanism for the intestinal atrophy caused by antimitotic drugs, endocrine failance due to the antimitotic drugs damages in the endocrine glands (pharmacological « hypophysectomy » and « castraction ») etc.

The selectivity of cytostatic action depends of the following factors:

a) the compound, its mode of action, the applied dosage, the localization and the speed of activation, its metabolites and excretion;

b) the sensitivity or resistance of the proliferated tissue;

c) the individual general condition of the patient, the degree of malnutrition, the integrity of defense mechanisms and the ability of detoxication and the regenerative capacity of hemopoiesis.

The action of cytostatic agents directed against specific cell functions of different cell systems develops distinct differences in clinical effects and toxicity among alkylating agents, antimetabolites and mitotic inhibitors. Comparative data of these compounds are given. Due to its selectivity of action each cytostatic agent possesses a specific optimal indication in hemoblastoses, neoplasias or immune reactions.

210 cases of polycythemia vera were observed over a period of 15 years. The majority of them received P32; treatment with Myleran instead of with radioactive phosphorus was instituted only recently. To a small number of patients chemotherapy was given alternately with P32. The differing response pattern to either kind of treatment and the possible interference of therapy with the natural development of the disease process are demonstrated in a few selected cases.