As more families opt for pre-implantation genetic diagnosis to screen embryos for inherited diseases, determining the regulatory and ethical guidelines to govern such screenings is “proving difficult,” the Chicago Tribune reports. Although the field of embryonic testing initially focused on identifying genetic defects that are certain to cause suffering or death early in life, it has broadened to include tests for genes linked to breast and ovarian cancer, which are not always fatal, occur later in life and affect 50% to 85% of those who carry the gene, according to the Tribune. The leading U.S. genetic diagnosis clinic, which is the largest in the world, conducted more than 1,800 screenings in 2008 “aimed at weeding out embryos that carried worrisome family conditions, from sickle cell anemia to cystic fibrosis,” the Tribune reports. Different countries vary in their regulation of PGD. In the U.S., doctors are allowed to select embryos for a particular sex, a practice that is not allowed in Great Britain, where each instance of PGD must be registered with the British Human Fertilization and Embryology Authority. BFEA has approved the use of PGD for about 70 genetic defects “after intensive public consultation about what is a serious enough problem to justify trying to eliminate it,” the Tribune reports. It is “significantly easier” to conduct PGD in the U.S. because the government only licenses clinics, not individual procedures, the Tribune reports. Mark Hughes, director of the Detroit-based Genesis Genetics Institute, said his company has tested for 171 genetic defects. In the U.S., “there is no approval mechanism,” Hughes said, adding, “No one is saying you can do this to save a sibling but you can’t do this for BRCA1,” a gene linked to breast cancer. According to a John Hopkins University study, nearly 40% of individuals surveyed believed that embryo screening should be regulated more closely for ethical reasons. An additional 19% said the screening should be banned altogether, for reasons ranging from the belief that discarding an embryo is immoral to concerns that selecting against certain diseases will devalue the lives of people already living with those conditions. Clare Williams, a bioethics specialist at Kings College London, said that during public hearings in Britain, “quite a lot of people felt there could well be treatment (for some conditions) by the time these children grow up, and then (their condition) won’t be an issue.” Some experts say it would be beneficial to place limits on the type of genetic defects doctors are allowed to screen for in the U.S., the Tribune reports. The Hopkins study found that, as of 2006, 65% of about 200 U.S. clinics offering embryo screenings allowed clients to choose the gender of the implanted embryo, regardless of the gender of existing children or whether the child was their first. The Tribune reports that such data and a California-based genetics lab’s recent announcement that it would be able to select eye and hair color have raised public concerns about genetic selection of embryos. The lab’s claims have been “disproved,” and many experts believe that expanded embryo screening “probably is not a slippery slope toward designer babies” because PGD is “costly and difficult,” there are a limited number of embryos to choose from and “finding one that includes a number of desired traits would be very difficult,” the Tribune reports. Hughes said the “things you might want to select for in a child — intelligence, athletic prowess, body stature — involve not single genes but many, many genes.” According to the Tribune, PGD, used in conjunction with in vitro fertilization, costs about $3,500 in the U.S. and twice that in Britain (Goering, Chicago Tribune, 3/25).
Tag Archives: Breast Cancer
The first baby to be screened for alterations in the breast cancer-causing gene, BRCA1, was born last week. The child was at risk from inheriting the gene from her father, who has women in three generations of his family who have been diagnosed with breast caner in their twenties as a result of inheriting the defective gene.
Paul Serhal, the fertility expert who treated the couple at the Assisted Conception unit of University College Hospital, London, said: ‘This little girl will not face the spectre of developing this genetic form of breast cancer or ovarian cancer in her adult life. The parents will have been spared the risk of inflicting this disease on their daughter. The lasting legacy is the eradication of the transmission of this form of cancer that has blighted these families for generations.’
The BRCA1 gene, when properly functioning, can help prevent breast cancer, but abnormal variations can significantly increase the risk of developing breast cancer. Females born with the affected gene face a 50-80 per cent risk of contacting breast cancer and a 40-60 per cent chance of developing ovarian cancer.
In 2006 the UK’s Human Fertilisation and Embryology Authority (HFEA) permitted fertility clinics to perform pre-implantation genetic diagnosis (PGD) – a procedure whereby embryos are tested for various conditions, the healthy ones are re-implanted and those that are affected are discarded – to test for this type of gene that makes carriers susceptible to a disease but that does not necessarily lead to disease in all cases. BRCA1 and BRCA2 account for around five per cent of breast cancers and it is thought that roughly 37,000 women in the UK carry BRCA1.
The couple concerned, who wish to remain anonymous, underwent IVF despite being fertile. A single cell was removed from the 11 embryos created when they were at the eight-cell stage and tested for the defective BRCA1 gene, revealing that only five of the embryos were free from the gene. Two of these were implanted into the mother’s womb, of which one, a girl, successfully implanted to develop until birth. The remaining three healthy embryos were frozen in case the parents want more children in the future. The six embryos carrying the defective BRCA1 gene were discarded.
Given that the breast cancer is increasingly curable and that carriers of the gene do not necessarily develop the disease (and vice versa), questions have been raised over the ethics of the procedure. Josephine Quintavalle, of the campaign group Comment on Reproductive Ethics (Core), told the BBC that she believes the procedure is a step too far, as it gives the message that ‘you are better off dead, than being born with this gene’. She added: ‘I hope 20 years down the line we will have eradicated breast cancer – not eradicated the carriers’.
Ovarian stimulation using gonadotropins and letrozole to preserve fertility in patients with breast cancer undergoing chemotherapy is unlikely to increase their risk for recurrence, say US researchers.
Kutluk Oktay, from the Center for Human Reproduction in New York, and colleagues evaluated 215 women with breast cancer for fertility preservation before adjuvant chemotherapy. Overall, 79 of the women underwent controlled ovarian stimulation (COS) for embryo or oocyte preservation, while the remainder served as controls.
An average of 10.3 oocytes were retrieved from COS patients, with 5.97 embryos or oocytes cryopreserved per patient.
The time between surgery and chemotherapy was significantly longer for patients who underwent IVF than control patients, at 45.08 versus 33.46 days. In patients who had COS, peak estradiol levels ranged from 58.4 to 1,166 pg/ml.
In the COS group, median follow-up after chemotherapy was 23.4 months, compared with 33.05 months in the control group. Recurrence occurred in 3.8 and 8.1 percent of COS and control patients, respectively, at a nonsignificant hazard ratio of 0.56.
The team concludes: “COS before embryo or oocyte cryopreservation is unlikely to result in a significant increase in recurrence of breast cancer compared with those who did not undergo ovarian stimulation, at least in the short term.”
A new, simple genetic test could improve the way breast cancer screening is approached in the UK, according to leading Cancer Research UK scientists. In a report published in the New England Journal of Medicine, the Cambridge University-based research team identified seven new gene variants that are associated with an increased risk of developing breast cancer. They found that by examining which of these variants a woman carries, they could classify the likelihood that she will develop breast cancer as being low, moderate or high. They suggest that this could affect the age at which a woman is encouraged to start having mammograms, and how frequently she subsequently has them.
Breast cancer is the second most common cancer in the UK affecting both men and women, and the risk of developing it is known to be partly influenced by an individual’s genetic makeup. Two well-known but rare gene variants in the genes BRCA-1 and BRCA-2 carry with them between a 36 and 85 per cent chance of developing breast cancer. Screening for these gene variants is currently offered to women with a strong family history of breast cancer. In the new study, the researchers pinpointed seven additional gene variants that are also associated with an increased susceptibility to breast cancer. Importantly, they found that although each of these gene variants individually carries only a mildly increased risk of developing breast cancer, having two or more of these gene variants in combination carries a much greater increased risk.
Currently, NHS mammograms are offered to all women over 50. The researchers propose that testing women for these genetic variants would enable a more targeted approach to breast cancer screening. Dr Paul Pharoah, a member of the Cambridge team explained: ‘We believe genetic testing has the potential to enable doctors to identify a woman at an increased risk of breast cancer who would benefit from mammography at an early age… and would also identify a 55-year-old woman with a low chance of breast cancer who possibly wouldn’t need such regular checks’.
The genetic test would involve just a simple mouth swab and the technology required is already available. However, the proposal was met with some caution. The researchers estimate that these seven gene variants account for only a third of the genes that influence the risk of developing breast cancer, so the test could not be considered to be comprehensive. Dr Sarah Cant of Breakthrough Breast Cancer commented that the study ‘raises interesting questions about how information on risk could be used to help decide who is eligible for screening’, adding: ‘However, breast cancer risk is affected by lifestyle and environment as well as genetics. These also need to be taken into account when determining risk’.