PRIMARY POLYCYTHAEMIA

The study comprises 75 patients with primary polycythaemia, treated at the Radiumhemmet in Stockholm. The patients were selected, in that a reasonable representation of four groups were aimed at: untreated, treated without myelofibrosis, treated with myelofibrosis, and treated patients in whom incipient transition into leucaemic phase was suspected clinically. All the treated patients had received 32 ‐P and/or Myleran. Chromosome analyses of blood and bone marrow were made once or several times. Twenty‐seven clones of bone marrow cells with abnormal chromosomal pattern were demonstrated in 26 patients. Twenty of the clones comprised more than 50 per cent of the cells analysed. It is especially emphasized that the F‐deletion previously described was demonstrated also in megakaryocytes in mitosis and, consequently, it must be supposed that the F‐deletion can be induced in primitive, multipotent haemopoietic cells. In order to clarify the influence of 32 P therapy on the genesis of the clones, studies into the relationship between some clinical parameters and the clone formations were made. The survey shows that the clones occur almost exclusively in patients treated with 32 P, that in our series the clones were not found in patients treated exclusively with Myleran, and that clones might appear in very few untreated patients. As regards the three groups of treated patients, it applies that generally the clones do not occur until the calculated dose per year is appreciable (> 2.5 mCi), and that the clones are found almost exclusively in patients treated over prolonged periods (> 2 years) with 32 P.