- Email: [email protected]
Head cooling in neonatal hypoxic-ischaemic encephalopathy
Comment
patients making a large randomised trial logistically difficult. Administration of GM-CSF at 30–60 g/m2 daily for 3 months with interferon has been shown to increase the rate of cytogenetic remission in patients with CML.10 However, in that study10 the GM-CSF doses used were higher than those used by Bocchia, suggesting that cytokine administration alone was less likely to account for the success of Bocchia’s trial. Testing direct cytotoxicity against primary leukaemic cells and tetramer binding for those alleles in which BCR-ABL fusion-region tetramers are available may have provided additional supporting data, although it is technically challenging when few leukaemic cells are available.4,11 It is clear that the introduction of imatinib, which is comparatively non-toxic yet has been associated with impressive clinical and cytogenetic responses,12 has revolutionised the therapy of CML, raising the obvious question: do we really need a vaccine for CML? Graham et al13 have suggested that quiescent CML Ph stem cells are relatively refractory to imatinib, and might serve as reservoirs for residual disease. These findings are supported by Bhatia et al14 who analysed 15 individuals with CML who achieved a complete cytogenetic response to imatinib therapy as determined by standard clinical criteria. However, when progenitors were purified and examined more stringently by fluorescent in-situ hybridisation and/or PCR, all had evidence of residual Ph cells. These data, combined with reports of imatinib resistance, support development of other strategies for treatment of this disease. Given the ease of administration, lack of toxicity, and early promise of efficacy, vaccine development against BCR-ABL or other CML-specific antigens appears to be a reasonable avenue for further investigation. In the meantime, we will eagerly await the results of disease-free survival in the group vaccinated with BCR-ABL peptide,
confirmatory studies by other investigators, and stay alert for rolling boulders. K K Wong Jr, *Saswati Chatterjee CML Disease Study Group, Division of Hematology & Hematopoietic Cell Transplantation (KKW Jr), and Division of Virology (SC), Beckman Research Institute, City of Hope National Medical Center, Duarte, CA 91024, USA [email protected] We declare that we have no conflict of interest. 1
2 3
4
5
6
7
8
9
10
11
12 13
14
Garcia-Manero G, Faderl S, O’Brien S, Cortes J, Talpaz M, Kantarjian HM. Chronic myelogenous leukemia: a review and update of therapeutic strategies. Cancer 2003; 98: 437–57. Wong S, Witte ON. The BCR-ABL story: bench to bedside and back. Annu Rev Immunol 2004; 22: 247–306. Chen W, Peace DJ, Rovira DK, You SG, Cheever MA. T-cell immunity to the joining region of p210BCR-ABL protein. Proc Natl Acad Sci USA 1992; 89: 1468–72. Clark RE, Dodi IA, Hill SC, et al. Direct evidence that leukemic cells present HLA-associated immunogenic peptides derived from the BCR-ABL b3a2 fusion protein. Blood 2001; 98: 2887–93. Pinilla-Ibarz J, Cathcart K, Korontsvit T, et al. Vaccination of patients with chronic myelogenous leukemia with bcr-abl oncogene breakpoint fusion peptides generates specific immune responses. Blood 2000; 95: 1781–87. Cathcart K, Pinilla-Ibarz J, Korontsvit T, et al. A multivalent bcr-abl fusion peptide vaccination trial in patients with chronic myeloid leukemia. Blood 2004; 103: 1037–42. Dong R, Cwynarski K, Entwistle A, et al. Dendritic cells from CML patients have altered actin organization, reduced antigen processing, and impaired migration. Blood 2003; 101: 3560–67. Dietz AB, Souan L, Knutson GJ, Bulur PA, Litzow MR, Vuk-Pavlovic S. Imatinib mesylate inhibits T-cell proliferation in vitro and delayed-type hypersensitivity in vivo. Blood 2004; 104: 1094–99. Appel S, Boehmler AM, Grunebach F, et al. Imatinib mesylate affects the development and function of dendritic cells generated from CD34+ peripheral blood progenitor cells. Blood 2004; 103: 538–44. Cortes J, Kantarjian H, O’Brien S, Kurzrock R, Keating M, Talpaz M. GM-CSF can improve the cytogenetic response obtained with interferon-alpha therapy in patients with chronic myelogenous leukemia. Leukemia 1998; 12: 860–64. Butt NM, Wang L, Abu-Eisha HM, Christmas SE, Clark RE. BCR-ABL-specific T cells can be detected in healthy donors and in chronic myeloid leukemia patients following allogeneic stem cell transplantation. Blood 2004; 103: 3245. Druker BJ. Chronic myeloid leukemia in the imatinib era. Semin Hematol 2003; 40 (suppl 2): 1–3. Graham SM, Jorgensen HG, Allan E, et al. Primitive, quiescent, Philadelphia-positive stem cells from patients with chronic myeloid leukemia are insensitive to STI571 in vitro. Blood 2002; 99: 319–25. Bhatia R, Holtz M, Niu N, et al. Persistence of malignant hematopoietic progenitors in chronic myelogenous leukemia patients in complete cytogenetic remission following imatinib mesylate treatment. Blood 2003; 101: 4701–77.
Head cooling in neonatal hypoxic-ischaemic encephalopathy Published online January 28, 2005 http://image.thelancet.com/ extras/04cmt333web.pdf See Articles page 663
632
Neonatal hypoxic-ischaemic encephalopathy in fullterm infants remains an important cause of perinatal mortality and later neurological disability worldwide.1 Although the risk of death or severe impairment is about 0·5–1 per 1000 livebirths in developed countries, rates 10–100 times greater are reported elsewhere.2,3
Causes include obstructed labour, umbilical cord compression or prolapse, and placental abruption. Many cases remain unexplained. The process of brain injury begins with the initial insult, but continues after resuscitation for days and even weeks. Our knowledge of the processes involved www.thelancet.com Vol 365 February 19, 2005
Comment
has come from two decades of studies, especially with magnetic resonance spectroscopy in both animal models and human infants.4–6 Despite this work, the management of hypoxic-ischaemic encephalopathy remains empirical and supportive in the absence of effective therapies. It is of great interest then that, in this issue of The Lancet, Peter Gluckman and colleagues report the results of the first large randomised trial of brain cooling as a therapy for hypoxic-ischaemic encephalopathy (the CoolCap study). During and after the initial insult, marked changes in cerebral metabolism are observed with a fall in highenergy phosphate levels, followed by recovery but often a further deterioration 6–24 h later. The severity of this secondary energy failure, which can last up to 72 h, is related to survival and subsequent neurodevelopmental outcome.4,5 Studies in animal models have shown that a reduction in body temperature of 3–4ºC is associated with improved histological and neurobehavioural outcomes.7,8 The exact mechanism responsible for any therapeutic benefit is unclear, but suppression of glutamate, free radicals, and other neurotransmitters or conservation of high-energy phosphates has been proposed. Limited studies in human infants to date appear to indicate that head cooling is safe, but have not shown efficacy in terms of reduction of mortality or major disability.9 At first sight the results of the CoolCap study are disappointing. The absolute rate reduction of 0·11 in death or major disability at 18 months in the treated group did not reach statistical significance. As anticipated, however, there was a significant relation between EEG findings at entry and outcome. There were more infants with the severest EEG changes and lowest Apgar scores at birth in the treatment group, and when this was adjusted for with logistic regression, the odds ratio for an unfavourable outcome was 0·57 and at borderline statistical significance. When the infants with the worst EEGs were removed from the analysis leaving an intermediately severe group, the absolute rate reduction of 0·18 was highly significant. Although not providing a definitive answer to the efficacy of early mild hypothermia in hypoxic-ischaemic encephalopathy, these findings do point to how future studies should be designed. The strong predictive value of the EEG means that simple clinical signs are probably not sufficiently precise to select a high-risk group for www.thelancet.com Vol 365 February 19, 2005
treatment. Equally, those infants with the severest EEG abnormalities should either not be included or EEG severity should be stratified before randomisation. Trials will inevitably have a greater or lesser power to show an effect of hypothermia depending on the proportion of the severest cases included. This proportion was 21% in the CoolCap study, but could be much higher with some clinical indicators for selection, such as seizures. Animal models show that the timing of the onset of cooling is critical, and that it must start before the onset of secondary energy failure at a few hours of age. Logistic considerations meant that in the CoolCap study only 12% of infants were cooled before 4 h, although encouragingly no effect of time of cooling between 4 and 6 h was seen. Many infants have failed to be recruited to hypothermia studies because of such delays; in future, consideration will need to be given to how such delays could be reduced. At least four similar-sized randomised trials are underway in the USA, UK, and Germany, and these are likely to report in the next year or two. Hopefully they will be similar enough to permit useful meta-analysis of their results. If the trends indicated by the CoolCap study are borne out, we shall soon have the first useful treatment for hypoxic-ischaemic encephalopathy. Such a treatment would be even more valuable because the technique is relatively low-tech and can be applied in parts of the world where hypoxic-ischaemic encephalopathy is a major neonatal problem. Richard Cooke Neonatal Unit, Liverpool Women's Hospital, Liverpool L8 7SS, UK [email protected] I chair the data-monitoring committee of the UK MRC TOBY trial of wholebody cooling for neonatal hypoxic encephalopathy. 1
2
3 4
5
6
Shankaran S, Woldt E, Koepke T, Bedard MP, Nandyal R. Acute neonatal morbidity and long-term central nervous system sequelae of perinatal asphyxia in preterm infants. Early Hum Dev 1991; 25: 135–48. Boo NY, Lye MS. Factors associated with clinically significant perinatal asphyxia in the Malaysian neonates: a case control study. J Trop Pediatr 1991; 38: 284–89. Kinotti SN. Asphyxia of the newborn in East, Central and Southern Africa. East Afr Med J 1993; 70: 422–33. Roth SC, Baudin J, Cady E, et al. Relation of deranged neonatal cerebral oxidative metabolism with neurodevelopmental outcome and head circumference at 4 years. Dev Med Child Neurol 1997; 39: 718–25. Hanrahan JD, Cox IJ, Azzopardi D, et al. Relation between proton magnetic resonance spectroscopy within 18 hours of birth asphyxia and neurodevelopment at 1 year of age. Dev Med Child Neurol 1999; 41: 76–82. Robertson NJ, Cox IJ, Cowan FM, Counsell SJ, Azzopardi D, Edwards AD. Cerebral intracellular lactic acidosis persisting months after neonatal
633
Comment
7
8
encephalopathy measured by magnetic resonance spectroscopy. Pediatr Res 1999; 46: 287–96. Colbourne F, Corbett D. Delayed postischaemic hypothermia: a six month survival study using behavioural and histological assessments of neuroprotection. J Neurosci 1995; 15: 7250–60. Bona E, Hagberg H, Loberg EM, Bagenholm R, Thoresen M. Protective
9
effects of moderate hypothermia after neonatal hypoxia-ischemia: short-and long-term outcome. Pediatr Res 1998; 43: 738–45. Jacobs S, Hunt R, Tarnow-Mordi W, Inder T, Davis P. Cooling for newborns with hypoxic ischaemic encephalopathy (Cochrane Review). In: The Cochrane Library, Issue 3. Chichester, UK: John Wiley and Sons, Ltd, 2004.
Gene-expression profiling in breast cancer See Articles page 671
In today’s Lancet, Yixin Wang and colleagues report a promising study showing the use of DNA microarray data for improving risk assessment for patients with lymph-node-negative breast cancer. The investigators identified a diagnostic test based on expression values from a subset of 76 genes (probe sets), measured by Affymetrix microarrays (U133a oligonucleotide gene chips). Briefly, this test, when used to suggest patients to receive adjuvant chemotherapy (at risk for distant metastases) would improve the specificity by 38% and 37%, in absolute difference, compared with the conventional St Gallen and NIH criteria, respectively, while keeping the same level of sensitivity. The potential advantages of improving tumour classification by expression profiling1 has been central for several large-scale breast cancer studies that have reported identification of signature gene lists with potential for prediction of clinical outcome over the past few years.2–7 The most striking finding when comparing the signature lists is the virtually complete lack of agreement in the included genes.8 To some extent this
Science Photo Library
Rights were not granted to include this image in electronic media. Please refer to the printed journal.
634
lack may be explained by differences in microarray technology (eg, probe type, printing technology) and selection of genes represented on the arrays, as well as experimental issues.9 Despite these obvious reasons for differing gene signatures, the microarrays used in different studies generally have several thousand genes in common and the underlying principles of the measurement technologies are the same; so we strongly believe the present lack of coherence still warrants further examination. In addition to differences in technology, the signatures reported have been aggregated from different sets of patients and for different objectives—ie, prediction goals. Sørlie et al2 and Ramaswamy et al7 focused on tumour subclassification, while van´t Veer et al5 and Wang and colleagues focused on survival predictors (disease-free and overall). However, both van´t Veer et al5 and Wang created their prediction signatures for metastasis-free survival (5 years) from patients with lymph-node-negative breast cancer with largely similar characteristics. When considering only the cases used to develop the classifiers and not the patients used for validation, the most evident difference was in patients’ age, and we do not believe the differences in signatures can be fully explained by the differences in patients’ characteristics alone. In the validation follow-up of van´t Veer et al,5 van de Vijver et al10 included a larger set of patients, including lymph-node-positive patients and a few that had received adjuvant systemic therapy. One possible confounder that deserves further investigation is the likely interdependency between oestrogen-receptor status, expression profile, and outcome status.11 Importantly, and in contrast to van´t Veer et al,5 Wang and colleagues provide a classification algorithm that considers oestrogen-receptor-positive patients separately from oestrogen-receptor-negative patients, and effectively classify expression profiles separately for receptor-positive and receptor-negative lymph-node-negative tumours. www.thelancet.com Vol 365 February 19, 2005
patients making a large randomised trial logistically difficult. Administration of GM-CSF at 30–60 g/m2 daily for 3 months with interferon has been shown to increase the rate of cytogenetic remission in patients with CML.10 However, in that study10 the GM-CSF doses used were higher than those used by Bocchia, suggesting that cytokine administration alone was less likely to account for the success of Bocchia’s trial. Testing direct cytotoxicity against primary leukaemic cells and tetramer binding for those alleles in which BCR-ABL fusion-region tetramers are available may have provided additional supporting data, although it is technically challenging when few leukaemic cells are available.4,11 It is clear that the introduction of imatinib, which is comparatively non-toxic yet has been associated with impressive clinical and cytogenetic responses,12 has revolutionised the therapy of CML, raising the obvious question: do we really need a vaccine for CML? Graham et al13 have suggested that quiescent CML Ph stem cells are relatively refractory to imatinib, and might serve as reservoirs for residual disease. These findings are supported by Bhatia et al14 who analysed 15 individuals with CML who achieved a complete cytogenetic response to imatinib therapy as determined by standard clinical criteria. However, when progenitors were purified and examined more stringently by fluorescent in-situ hybridisation and/or PCR, all had evidence of residual Ph cells. These data, combined with reports of imatinib resistance, support development of other strategies for treatment of this disease. Given the ease of administration, lack of toxicity, and early promise of efficacy, vaccine development against BCR-ABL or other CML-specific antigens appears to be a reasonable avenue for further investigation. In the meantime, we will eagerly await the results of disease-free survival in the group vaccinated with BCR-ABL peptide,
confirmatory studies by other investigators, and stay alert for rolling boulders. K K Wong Jr, *Saswati Chatterjee CML Disease Study Group, Division of Hematology & Hematopoietic Cell Transplantation (KKW Jr), and Division of Virology (SC), Beckman Research Institute, City of Hope National Medical Center, Duarte, CA 91024, USA [email protected] We declare that we have no conflict of interest. 1
2 3
4
5
6
7
8
9
10
11
12 13
14
Garcia-Manero G, Faderl S, O’Brien S, Cortes J, Talpaz M, Kantarjian HM. Chronic myelogenous leukemia: a review and update of therapeutic strategies. Cancer 2003; 98: 437–57. Wong S, Witte ON. The BCR-ABL story: bench to bedside and back. Annu Rev Immunol 2004; 22: 247–306. Chen W, Peace DJ, Rovira DK, You SG, Cheever MA. T-cell immunity to the joining region of p210BCR-ABL protein. Proc Natl Acad Sci USA 1992; 89: 1468–72. Clark RE, Dodi IA, Hill SC, et al. Direct evidence that leukemic cells present HLA-associated immunogenic peptides derived from the BCR-ABL b3a2 fusion protein. Blood 2001; 98: 2887–93. Pinilla-Ibarz J, Cathcart K, Korontsvit T, et al. Vaccination of patients with chronic myelogenous leukemia with bcr-abl oncogene breakpoint fusion peptides generates specific immune responses. Blood 2000; 95: 1781–87. Cathcart K, Pinilla-Ibarz J, Korontsvit T, et al. A multivalent bcr-abl fusion peptide vaccination trial in patients with chronic myeloid leukemia. Blood 2004; 103: 1037–42. Dong R, Cwynarski K, Entwistle A, et al. Dendritic cells from CML patients have altered actin organization, reduced antigen processing, and impaired migration. Blood 2003; 101: 3560–67. Dietz AB, Souan L, Knutson GJ, Bulur PA, Litzow MR, Vuk-Pavlovic S. Imatinib mesylate inhibits T-cell proliferation in vitro and delayed-type hypersensitivity in vivo. Blood 2004; 104: 1094–99. Appel S, Boehmler AM, Grunebach F, et al. Imatinib mesylate affects the development and function of dendritic cells generated from CD34+ peripheral blood progenitor cells. Blood 2004; 103: 538–44. Cortes J, Kantarjian H, O’Brien S, Kurzrock R, Keating M, Talpaz M. GM-CSF can improve the cytogenetic response obtained with interferon-alpha therapy in patients with chronic myelogenous leukemia. Leukemia 1998; 12: 860–64. Butt NM, Wang L, Abu-Eisha HM, Christmas SE, Clark RE. BCR-ABL-specific T cells can be detected in healthy donors and in chronic myeloid leukemia patients following allogeneic stem cell transplantation. Blood 2004; 103: 3245. Druker BJ. Chronic myeloid leukemia in the imatinib era. Semin Hematol 2003; 40 (suppl 2): 1–3. Graham SM, Jorgensen HG, Allan E, et al. Primitive, quiescent, Philadelphia-positive stem cells from patients with chronic myeloid leukemia are insensitive to STI571 in vitro. Blood 2002; 99: 319–25. Bhatia R, Holtz M, Niu N, et al. Persistence of malignant hematopoietic progenitors in chronic myelogenous leukemia patients in complete cytogenetic remission following imatinib mesylate treatment. Blood 2003; 101: 4701–77.
Head cooling in neonatal hypoxic-ischaemic encephalopathy Published online January 28, 2005 http://image.thelancet.com/ extras/04cmt333web.pdf See Articles page 663
632
Neonatal hypoxic-ischaemic encephalopathy in fullterm infants remains an important cause of perinatal mortality and later neurological disability worldwide.1 Although the risk of death or severe impairment is about 0·5–1 per 1000 livebirths in developed countries, rates 10–100 times greater are reported elsewhere.2,3
Causes include obstructed labour, umbilical cord compression or prolapse, and placental abruption. Many cases remain unexplained. The process of brain injury begins with the initial insult, but continues after resuscitation for days and even weeks. Our knowledge of the processes involved www.thelancet.com Vol 365 February 19, 2005
Comment
has come from two decades of studies, especially with magnetic resonance spectroscopy in both animal models and human infants.4–6 Despite this work, the management of hypoxic-ischaemic encephalopathy remains empirical and supportive in the absence of effective therapies. It is of great interest then that, in this issue of The Lancet, Peter Gluckman and colleagues report the results of the first large randomised trial of brain cooling as a therapy for hypoxic-ischaemic encephalopathy (the CoolCap study). During and after the initial insult, marked changes in cerebral metabolism are observed with a fall in highenergy phosphate levels, followed by recovery but often a further deterioration 6–24 h later. The severity of this secondary energy failure, which can last up to 72 h, is related to survival and subsequent neurodevelopmental outcome.4,5 Studies in animal models have shown that a reduction in body temperature of 3–4ºC is associated with improved histological and neurobehavioural outcomes.7,8 The exact mechanism responsible for any therapeutic benefit is unclear, but suppression of glutamate, free radicals, and other neurotransmitters or conservation of high-energy phosphates has been proposed. Limited studies in human infants to date appear to indicate that head cooling is safe, but have not shown efficacy in terms of reduction of mortality or major disability.9 At first sight the results of the CoolCap study are disappointing. The absolute rate reduction of 0·11 in death or major disability at 18 months in the treated group did not reach statistical significance. As anticipated, however, there was a significant relation between EEG findings at entry and outcome. There were more infants with the severest EEG changes and lowest Apgar scores at birth in the treatment group, and when this was adjusted for with logistic regression, the odds ratio for an unfavourable outcome was 0·57 and at borderline statistical significance. When the infants with the worst EEGs were removed from the analysis leaving an intermediately severe group, the absolute rate reduction of 0·18 was highly significant. Although not providing a definitive answer to the efficacy of early mild hypothermia in hypoxic-ischaemic encephalopathy, these findings do point to how future studies should be designed. The strong predictive value of the EEG means that simple clinical signs are probably not sufficiently precise to select a high-risk group for www.thelancet.com Vol 365 February 19, 2005
treatment. Equally, those infants with the severest EEG abnormalities should either not be included or EEG severity should be stratified before randomisation. Trials will inevitably have a greater or lesser power to show an effect of hypothermia depending on the proportion of the severest cases included. This proportion was 21% in the CoolCap study, but could be much higher with some clinical indicators for selection, such as seizures. Animal models show that the timing of the onset of cooling is critical, and that it must start before the onset of secondary energy failure at a few hours of age. Logistic considerations meant that in the CoolCap study only 12% of infants were cooled before 4 h, although encouragingly no effect of time of cooling between 4 and 6 h was seen. Many infants have failed to be recruited to hypothermia studies because of such delays; in future, consideration will need to be given to how such delays could be reduced. At least four similar-sized randomised trials are underway in the USA, UK, and Germany, and these are likely to report in the next year or two. Hopefully they will be similar enough to permit useful meta-analysis of their results. If the trends indicated by the CoolCap study are borne out, we shall soon have the first useful treatment for hypoxic-ischaemic encephalopathy. Such a treatment would be even more valuable because the technique is relatively low-tech and can be applied in parts of the world where hypoxic-ischaemic encephalopathy is a major neonatal problem. Richard Cooke Neonatal Unit, Liverpool Women's Hospital, Liverpool L8 7SS, UK [email protected] I chair the data-monitoring committee of the UK MRC TOBY trial of wholebody cooling for neonatal hypoxic encephalopathy. 1
2
3 4
5
6
Shankaran S, Woldt E, Koepke T, Bedard MP, Nandyal R. Acute neonatal morbidity and long-term central nervous system sequelae of perinatal asphyxia in preterm infants. Early Hum Dev 1991; 25: 135–48. Boo NY, Lye MS. Factors associated with clinically significant perinatal asphyxia in the Malaysian neonates: a case control study. J Trop Pediatr 1991; 38: 284–89. Kinotti SN. Asphyxia of the newborn in East, Central and Southern Africa. East Afr Med J 1993; 70: 422–33. Roth SC, Baudin J, Cady E, et al. Relation of deranged neonatal cerebral oxidative metabolism with neurodevelopmental outcome and head circumference at 4 years. Dev Med Child Neurol 1997; 39: 718–25. Hanrahan JD, Cox IJ, Azzopardi D, et al. Relation between proton magnetic resonance spectroscopy within 18 hours of birth asphyxia and neurodevelopment at 1 year of age. Dev Med Child Neurol 1999; 41: 76–82. Robertson NJ, Cox IJ, Cowan FM, Counsell SJ, Azzopardi D, Edwards AD. Cerebral intracellular lactic acidosis persisting months after neonatal
633
Comment
7
8
encephalopathy measured by magnetic resonance spectroscopy. Pediatr Res 1999; 46: 287–96. Colbourne F, Corbett D. Delayed postischaemic hypothermia: a six month survival study using behavioural and histological assessments of neuroprotection. J Neurosci 1995; 15: 7250–60. Bona E, Hagberg H, Loberg EM, Bagenholm R, Thoresen M. Protective
9
effects of moderate hypothermia after neonatal hypoxia-ischemia: short-and long-term outcome. Pediatr Res 1998; 43: 738–45. Jacobs S, Hunt R, Tarnow-Mordi W, Inder T, Davis P. Cooling for newborns with hypoxic ischaemic encephalopathy (Cochrane Review). In: The Cochrane Library, Issue 3. Chichester, UK: John Wiley and Sons, Ltd, 2004.
Gene-expression profiling in breast cancer See Articles page 671
In today’s Lancet, Yixin Wang and colleagues report a promising study showing the use of DNA microarray data for improving risk assessment for patients with lymph-node-negative breast cancer. The investigators identified a diagnostic test based on expression values from a subset of 76 genes (probe sets), measured by Affymetrix microarrays (U133a oligonucleotide gene chips). Briefly, this test, when used to suggest patients to receive adjuvant chemotherapy (at risk for distant metastases) would improve the specificity by 38% and 37%, in absolute difference, compared with the conventional St Gallen and NIH criteria, respectively, while keeping the same level of sensitivity. The potential advantages of improving tumour classification by expression profiling1 has been central for several large-scale breast cancer studies that have reported identification of signature gene lists with potential for prediction of clinical outcome over the past few years.2–7 The most striking finding when comparing the signature lists is the virtually complete lack of agreement in the included genes.8 To some extent this
Science Photo Library
Rights were not granted to include this image in electronic media. Please refer to the printed journal.
634
lack may be explained by differences in microarray technology (eg, probe type, printing technology) and selection of genes represented on the arrays, as well as experimental issues.9 Despite these obvious reasons for differing gene signatures, the microarrays used in different studies generally have several thousand genes in common and the underlying principles of the measurement technologies are the same; so we strongly believe the present lack of coherence still warrants further examination. In addition to differences in technology, the signatures reported have been aggregated from different sets of patients and for different objectives—ie, prediction goals. Sørlie et al2 and Ramaswamy et al7 focused on tumour subclassification, while van´t Veer et al5 and Wang and colleagues focused on survival predictors (disease-free and overall). However, both van´t Veer et al5 and Wang created their prediction signatures for metastasis-free survival (5 years) from patients with lymph-node-negative breast cancer with largely similar characteristics. When considering only the cases used to develop the classifiers and not the patients used for validation, the most evident difference was in patients’ age, and we do not believe the differences in signatures can be fully explained by the differences in patients’ characteristics alone. In the validation follow-up of van´t Veer et al,5 van de Vijver et al10 included a larger set of patients, including lymph-node-positive patients and a few that had received adjuvant systemic therapy. One possible confounder that deserves further investigation is the likely interdependency between oestrogen-receptor status, expression profile, and outcome status.11 Importantly, and in contrast to van´t Veer et al,5 Wang and colleagues provide a classification algorithm that considers oestrogen-receptor-positive patients separately from oestrogen-receptor-negative patients, and effectively classify expression profiles separately for receptor-positive and receptor-negative lymph-node-negative tumours. www.thelancet.com Vol 365 February 19, 2005