Data sharing among data monitoring committees and responsibilities to patients and science.

Over the past three decades it has become increasingly recognized that systematic assessment of as high a proportion as possible of relevant research evidence is needed to protect the best interests of patients and the public. For example, this principle is manifested in clinical guidelines and, increasingly, in the design and monitoring of new research. For scientific and ethical reasons, those responsible for monitoring the progress of ongoing clinical trials may need to seek unpublished and interim data to protect the interests of actual or potential participants in research. The challenge facing data monitoring committees has received relatively little attention, however. In this paper we review some of the commentaries on the issue and the few accounts of actual data monitoring committee experiences. We then present details of our own recent experience as members of the data monitoring committee for the BOOST-II UK trial (ISRCTN:0084226), one of five concurrent trials assessing the level of arterial oxygen which should be targeted in the care of very premature neonates. We conclude that efficient protection both of the interests of actual or potential participants in research and of science requires that data monitoring committees have access to all relevant research, including unpublished and interim data.

A patient with mosaic partial trisomy 18 resulting from dicentric chromosome breakage.

We present a patient with minor dysmorphic features and a mosaic karyotype with two different abnormal cell lines, both involving abnormalities of chromosome 18. Twenty percent of cells studied (4/20) had 46 chromosomes with a large derivative pseudoisodicentric chromosome 18. This chromosome was deleted for 18pter and duplicated for part of proximal 18p (18p11.2 based on fluorescence in situ hybridization (FISH) studies and all of 18q. The two copies of portions of chromosome 18 were fused in an inverted fashion (duplicated for 18qter->18p11.3). The smaller der(18) was present in 80% of cells studied (16/20) and had a normal q-arm, while the p-arm was missing the subtelomere region but had duplication of a part of 18p. FISH studies showed that the larger derivative 18 contained the 18q subtelomere at each end, but the 18p subtelomere was absent, consistent with fusion of two regions within 18p resulting in deletion of the subtelomeric regions. The smaller der(18) was also missing the 18p subtelomere (with normal 18q as expected). Further testing with BAC clones mapping within 18p11.2 showed that these sequences were duplicated and inverted in both of the der(18)s. These findings lead us to hypothesize that the smaller der(18) was derived from the larger, dicentric 18 following anaphase bridge formation, with breakage distal to the duplicated segment.