The first PGD for inherited predisposition to cancer was performed for couples carrying p53 tumor-suppressor gene mutations [9], a cellular marker associated with a strong predisposition to many malignancies. Two couples presented for PGD, one with the maternally and one with the paternally derived p53 tumor-suppressor mutation. The father had a mis-sense mutation due to a G to A transposition in exon 5 of the p53 tumor-suppressor gene; this resulted in a change from Arginine to Histidine at amino acid residue 175 of the protein [10]. When he presented to our center, the patient was aged 38 and had been diagnosed with Li–Fraumeni syndrome (LFS). Moreover, he was diagnosed with rhabdomyosarcoma of the right shoulder at the age of two followed by right upper extremity amputation. At age 31, he was also diagnosed with a high-grade leiomyosarcoma of the bladder and underwent a radical cystoprostatectomy. His mother was diagnosed with leiomyosarcoma at the age 37.

In the other couple, the 39-year-old mother with LFS was a carrier of 902insC mutation of the p53 tumor-suppressor gene, representing an insertion of C in exon 8. She was diagnosed with breast cancer at age 30, followed by bilateral mastectomy. She also had thyroid cystic carcinoma, which was also excised. Her mother died from a stomach cancer at age 51. One of her sisters diagnosed with breast cancer at 48 followed by mastectomy also died at age 51. Two of her four brothers were diagnosed with bone or brain tumor in their teens.

PGD for the maternal 902insC mutation was done by DNA analysis of PB1 and PB2, removed sequentially following maturation and fertilization of oocytes. The paternal G524A mutation was tested by DNA analysis of single blastomeres, removed from eight-cell embryos. Based on both mutation and STR analysis, unaffected embryos were preselected for transfer back to the patients. PGD resulted in a singleton pregnancy and birth of a mutation-free child in a couple with the paternally derived G525A mutation, demonstrating a potential for the preselection of the mutation-free embryos and the establishment of an unaffected pregnancy, rather than testing and termination of an ongoing pregnancy in utero. Because many at-risk couples have had such an unfortunate experience of repeated prenatal diagnoses and termination of affected pregnancies, naturally they regard PGD as their only hope for having healthy children of their own, despite having to undergo IVF.

Another cancer for which embryo testing with PGD has been successfully applied for many years is neurofibromatosis (NF). This is a relatively common autosomal-dominant neurological disorder with at least two distinct major forms, including NF type I (NF1), which is more common (1:4,000) and characterized by fibromatous skin tumors with cafe-au-lait spots (“Von Recklinghausen disease”), and NF type II (NF2), which is less common (1:100,000) and characterized by bilateral acoustic neuromas, meningiomas, schwannomas, and neurofibromas [11].

In our experience, of 36 couples who presented for PGD specifically for NF, 32 were at risk for producing a child with NF1 and 4 couples were at risk to have offspring with the NF2 mutation. As a result of IVF and PGD at this center, 31 healthy babies were born demonstrating the acceptable diagnostic accuracy of PGD of NF1 and NF2. So genetic counseling services may consider informing patients at risk of having children with a strong genetic predisposition to NF about the availability of PGD, without which these couples may remain childless because of their hesitancy to avail of standard prenatal diagnosis and possible pregnancy termination.

At present the most common cancer for which PGD has been performed is inherited breast cancer [3, 4, 12, 13]. Almost half of inherited breast cancers are caused by BRCA1 and BRCA2, and these mutations represent the primary indication for 76 PGD cycles here (Table 15.1). A total of 93 embryos free from these mutations were preselected for transfer in 54 cycles, resulting in birth of 40 children without predisposition to breast cancer.

As seen in Table 15.1, the other frequent indication was FAP. Patients with FAP usually present with colorectal cancer in early adult life, secondary to extensive adenomatous polyps of the colon, determined by mutation of adenomatous polyposis coli (APC) gene located on chromosome 5 (5q21-q22). Over 826 germline mutations have been found in families with FAP, causing a premature truncation of the APC protein (through single amino acid substitutions or frameshifts), with most common mutation being a 5-bp deletion resulting in a frameshift mutation at codon 1309. These APC mutations lead to a premalignant disease with one or more polyps progressing through dysplasia to malignancy with a median age at diagnosis of 40 years. Because the mutations in APC gene are almost totally penetrant (although with striking variation in expression), even presymptomatic diagnosis and treatment of carriers cannot exclude the progression of polyps to malignancy, thus making PGD an attractive approach for couples carrying APC mutations.

Eight cycles have been performed for VHL. These treatments resulted in the birth of six babies free of genes predisposing to VHL—a severe cancer syndrome with age-related penetrance characterized by hemangiomablastomas of the brain, spinal cord and retina, bilateral renal cysts, renal carcinoma, pheochromocytoma, and pancreatic cysts. Depending on the combination of these clinical features, four different types of the disease have been described. The gene responsible for VHL syndrome consists of three exons and is located on chromosome 3 (3p26-p25). Specific VHL gene mutations have been correlated to clinical phenotype. Its normal gene product is a tumor-suppressor protein, which is expressed in most cells and has a variety of functions, including transcriptional and posttranscriptional regulation. More than 300 germline mutations have been identified in families with VHL syndrome, consisting of partial or complete gene deletions, and frameshift, nonsense, mis-sense, and splice-site mutations, most commonly affecting codon 167. Mutations in the VHL gene either prevent its expression completely or lead to the expression of an abnormal protein. Because 80 % of VHL cases are familial, PGD is clearly an attractive option for couples carrying these mutations to avoid transmission of these serious tumor-suppressor gene errors to their offspring.

Nineteen cycles have been completed for inherited predisposition to RB, caused by the germline mutations in the RB1 gene located on chromosome 13 (q14.1-q14.2). RB is a malignant tumor of retina, which occurs in cells with cancer-predisposing mutations usually before the age of 5 years. More than half of patients have the unilateral RB, which may be diagnosed at 24 months, while the bilateral RB is recognizable as early as at 15 months, using direct ophthalmoscopy. The majority of cases are due to a point mutation in coding regions of the RB1 gene, while partial deletions of the gene have also been described. Over 200 distinct mutations have been reported, with the majority resulting in premature termination codon, usually through single base substitutions or frameshift or splice mutations, scattered throughout exon 1 to exon 25 of the RB1 gene and its promoter region. Such mutations result in loss of the cell cycle regulation function of the RB1 protein and are nearly completely penetrant in nonsense and frameshift mutations, making PGD an important option for couples at risk of this disorder.

At our institution, IVF with PGD has been undertaken for 11 patients at risk for producing offspring predisposed to RB. Unaffected embryos were preselected and transferred, resulting in clinical pregnancies in seven cases, with birth of seven healthy babies free from the mutant gene predisposing to RB.

A single PGD cycle was performed for a patient carrying the hSNF5 mutation, which predisposes to a very rare type of brain tumor found in sporadic rhabdoid tumors of the central nervous system [8]. Rhabdoid tumors are known to be highly malignant neoplasms usually occurring in children under 2 years of age. Although rhabdoid tumors determined by truncating mutations of the hSNF5 gene are mainly de novo and therefore were not previously thought to be present in parents of affected children, a first familial case of posterior fossa brain tumor has been described in two generations [14]. The proband presented at the age of 18 months with a cerebellar malignant rhabdoid tumor. Although the parents were healthy, the child’s maternal uncle died at age 2 from a posterior fossa choroids plexus carcinoma, and her grandfather’s sibling also died as an infant from a brain tumor, suggesting the presence of a germline mutation. The couple presented for PGD in order to have a pregnancy free from hSNF5 mutation, also avoiding the birth of a second child with a brain tumor. The mutation was due to G to A substitution in a donor splice site of exon 7, which alters the conserved GT sequence at the beginning of the intron violating the GT rule for splice-site recognition. In this unique case, the mother was unaffected but her daughter who inherited the mutation had a brain tumor. Because the mutation was also detected in DNA from her uncle’s tumor, this suggested the risk of transmitting the mutation to the next child. Accordingly, PB1 and PB2 were removed in this case to identify mutation-free oocytes during IVF.

As summarized in Table 15.1, the range of PGD specifically for malignant disease is expanding and most IVF cycles incorporating this technique result in birth of children free of genes which predispose to these hereditary disorders. With current advancements in molecular diagnosis of such cancers (including sequencing of the genes involved in malignancy), it is likely that this application for PGD will become even more prominent. Despite extensive discussions concerning the ethical and legal issues involved in PGD for late-onset disorders with genetic predisposition, an increasing number of patients have come to regard the procedure not just as their best option—but as their only option—to experience a pregnancy of their own, without reliance on donor gametes. Thus, IVF with PGD in these cases permits patients to sidestep a potentially difficult decision to terminate a pregnancy at high risk of being affected with a heritable cancer.

Of note, because such diseases present beyond early childhood and even later may not be expressed in 100 % of the cases, the application of PGD for this group of disorders remains highly controversial. However, initial experience with PGD specifically in these settings shows that the availability of this technology can allow couples to undergo single embryo transfer and have a healthy baby. Otherwise, these patients would have never attempted pregnancy without PGD. This may be further demonstrated by PGD performed for genetic predisposition to Alzheimer disease (AD) [15].