Genetic Cancer Family History: IVF Screening in Thailand – PGT-M Technology to Block Hereditary Risk

AI Summary

Real Consultation Scenario

A 36-year-old woman sat down in the clinic and took out her mother's medical records from a file folder: diagnosed with breast cancer at 51, died of ovarian cancer at 58. She herself tested positive for the BRCA1 gene and had already undergone a preventive mastectomy. She asked directly: "I want to do IVF in Thailand. Can I screen out this gene so my child won't get it?"

This question is becoming increasingly common in genetic counseling and reproductive clinics. Embryo screening for hereditary cancer through IVF technology has a well-established pathway in reproductive medicine. The core is PGT-M technology, Preimplantation Genetic Testing for Monogenic Diseases. Below, we break down the technical principles, applicable conditions, process, timeline, costs, and common misconceptions.

Core Technology for IVF Screening of Hereditary Cancer – PGT-M

Direct Answer: IVF screening for hereditary cancer in Thailand corresponds medically to PGT-M (Preimplantation Genetic Testing for Monogenic Diseases). This technology is suitable for hereditary tumor syndromes with a clear pathogenic gene. After obtaining embryos through in vitro fertilization, genetic testing is performed on the embryos before transfer to select those that do not carry the pathogenic gene, thereby preventing the transmission of hereditary cancer to offspring.

Not everyone with a family history of cancer is suitable for PGT-M. A key condition must be met: the proband (the first diagnosed patient in the family) must have had the pathogenic gene mutation identified through genetic testing. If there is a family history of cancer but no clear pathogenic mutation has been found through genetic testing, PGT-M cannot be performed.

Which Hereditary Cancers Are Suitable for PGT-M

Clinically, the most well-established hereditary tumor syndromes for PGT-M include:

• Hereditary Breast-Ovarian Cancer Syndrome (BRCA1/BRCA2 gene mutations)
• Lynch Syndrome (MLH1, MSH2, MSH6, PMS2 gene mutations, leading to colorectal cancer, endometrial cancer, etc.)
• Li-Fraumeni Syndrome (TP53 gene mutation)
• Familial Adenomatous Polyposis (APC gene mutation)
• Hereditary Diffuse Gastric Cancer (CDH1 gene mutation)
• Multiple Endocrine Neoplasia (RET, MEN1 gene mutations, etc.)

The common characteristics of the above syndromes are: clear pathogenic genes, high penetrance, and clear inheritance patterns (mainly autosomal dominant), meeting the criteria for PGT-M indications.

Doctor's Perspective: Decision Logic and Evaluation Points for PGT-M

From a reproductive medicine perspective, PGT-M is an effective means to block hereditary cancer, but strict evaluation of indications is necessary. I often tell patients: PGT-M addresses the 'genetic risk' issue, not the 'fertility' issue. A complete evaluation includes three levels:

• Genetic Evaluation: Confirm the pathogenic gene mutation in the family and that it can be detected by PGT-M. Requires the proband's genetic report, or confirmation that you carry the pathogenic mutation.
• Reproductive Function Evaluation: No matter how advanced the screening technology, embryos must ultimately be obtained through IVF. The woman needs assessment of ovarian reserve (AMH, FSH, antral follicle count), and the man needs a semen analysis. Diminished ovarian reserve (AMH < 1.0 ng/mL, FSH > 10 IU/L) directly affects the number of eggs and embryos obtained, thereby affecting the probability of having usable embryos after screening.
• Embryo Testing Feasibility Evaluation: PGT-M requires designing detection probes for specific gene mutations, usually requiring DNA samples from the proband or parents. Some mutation types (e.g., large deletions, dynamic mutations) are difficult to detect and require prior evaluation by the genetic laboratory.

Complete Process for PGT-M Screening in Thailand

The entire process for IVF screening of hereditary cancer in Thailand is roughly divided into the following stages:

Stage 1: Genetic Preparation (Completed in Home Country)

• Genetic counseling to confirm the family inheritance pattern and draw a pedigree chart.
• Genetic testing of the proband or yourself to identify the pathogenic gene mutation site.
• Obtain the original genetic testing report (in Chinese/English or English). Some Thai centers require reports from CAP or CLIA certified laboratories.
• Provide DNA samples from the proband or parents for subsequent probe design for embryo testing.

Stage 2: Contact and Registration with Thai Fertility Center

• Choose a Thai fertility center and submit the genetic report for pre-review.
• After the center confirms it can perform PGT-M for that gene site, schedule an initial consultation.
• The woman undergoes fertility assessment (AMH, FSH, vaginal ultrasound for antral follicle count), infectious disease screening, and chromosome karyotype analysis.
• The man undergoes semen analysis, infectious disease screening, and chromosome karyotype analysis.
• Sign informed consent forms, including the accuracy and limitations of PGT-M testing, and handling of surplus embryos.

Stage 3: Ovarian Stimulation and Egg Retrieval

• Based on the woman's ovarian function and follicle development, an individualized ovarian stimulation protocol is designed (mainly antagonist or short protocol).
• Ovarian stimulation lasts about 10-12 days, during which follicle development and hormone levels are monitored.
• Egg retrieval is performed 36 hours after hCG injection, along with sperm collection.

Stage 4: Embryo Culture and Biopsy

• After fertilization, embryos are cultured to the blastocyst stage (days 5-6).
• Trophectoderm biopsy is performed on the blastocysts, taking 3-5 cells for genetic testing.
• After biopsy, the blastocysts are cryopreserved (frozen embryos) while awaiting test results.

Stage 5: PGT-M Genetic Testing

• Biopsied cells are sent to a genetic laboratory for testing, typically using NGS (Next-Generation Sequencing) or PCR-based methods.
• Embryos are tested for the presence of the pathogenic gene mutation, and concurrent aneuploidy screening (PGT-A) is performed to select embryos with a normal chromosome number that do not carry the pathogenic gene.
• The testing period is approximately 2-4 weeks.

Stage 6: Embryo Transfer

• Based on the test results, 1-2 embryos that are free of the pathogenic gene and chromosomally normal are selected for transfer.
• Endometrial preparation is required before transfer, typically using a hormone replacement cycle or natural cycle.
• Blood hCG test is done 12-14 days after transfer to confirm pregnancy.
• After pregnancy, prenatal diagnosis (chorionic villus sampling or amniocentesis) is recommended to verify the embryo test results.

Timeline: How Long from Preparation to Transfer

The timeline for the entire cycle can be summarized in the table below:

Special note: The duration of PGT-M testing is a key variable affecting the total cycle. Different laboratories have different capabilities and schedules. It is advisable to confirm the testing schedule with the laboratory before starting ovarian stimulation.

Differences in PGT-M Policies and Technologies Across Countries

Choosing Thailand for IVF screening of hereditary cancer has several notable differences compared to China or the United States:

Thailand's main advantages are: broader policy coverage, relatively smooth process for applying PGT-M for hereditary cancer; costs between those of China and the US; some fertility centers have extensive experience with genetic cases. However, it is important to note that the quality of fertility centers in Thailand varies, and the qualifications and testing capabilities of genetic laboratories need careful verification.

Easily Overlooked Details

In clinical practice, several details are often overlooked but have a significant impact on outcomes:

• Validity of Genetic Report: Some Thai centers require genetic testing reports from CAP or CLIA certified laboratories. If genetic testing was done at a regular hospital in your home country, you may need to confirm in advance whether the report is accepted, or if retesting is needed.
• Obtaining DNA Samples from the Proband: Probe design for PGT-M usually requires a DNA sample from the proband (the first diagnosed patient in the family). If the proband has passed away or a sample is unavailable, haplotyping may need to be done using other methods, which increases testing difficulty and uncertainty.
• Accuracy of Embryo Testing is Not 100%: The accuracy of PGT-M is between 97-99%. There are risks of allele dropout, mosaicism, etc., leading to misdiagnosis. Therefore, prenatal diagnosis is recommended after transfer.
• Impact of Ovarian Reserve on Outcome: PGT-M is a "screening" process, not a "repair" process. The more embryos available, the higher the probability of finding a healthy one. If AMH is low (< 1.0 ng/mL) or age is advanced (> 40 years), multiple ovarian stimulation cycles may be needed to obtain a sufficient number of embryos.

Common Pitfalls

• Skipping Genetic Counseling and Going Directly to Thailand: Without completing genetic evaluation and testing in your home country, you may arrive in Thailand only to find that genetic information is incomplete, making it impossible to start PGT-M, wasting both time and money.
• Choosing a Facility Without Genetic Lab Qualifications: Some agencies or small clinics claim to offer genetic screening but actually send embryo biopsy samples to labs without relevant qualifications, compromising testing quality.
• Ignoring Embryo Chromosome Screening: Focusing only on the single gene mutation without concurrent aneuploidy screening (PGT-A). The transferred embryo may not carry the pathogenic gene but could be chromosomally abnormal, leading to implantation failure or miscarriage.
• Underestimating the Probability of a "Healthy Embryo": In autosomal dominant disorders, theoretically 50% of embryos may carry the pathogenic gene and 50% may be normal. However, combined with the rate of chromosomal abnormalities (which increases with age), the actual proportion of transferable embryos is lower. Women over 35 should be mentally prepared for the possibility of needing multiple ovarian stimulation cycles.

Case Scenario: IVF Screening Path for a BRCA1 Mutation Carrier in Thailand

Returning to the opening case. Ms. Zhang, 36 years old, has a heterozygous mutation in the BRCA1 gene c.68_69delAG (a common pathogenic mutation). Her mother has passed away. She has already undergone a preventive mastectomy. Her AMH is 1.8 ng/mL, FSH 8.5 IU/L, and antral follicle count is 10.

Her screening path was:

• Genetic counseling in her home country: Confirmed the mutation is clearly pathogenic and meets PGT-M indications. Since her mother had passed away, haplotyping was done using her blood sample and her father's sample to complete probe design.
• Chose a Thai center with a genetics team; submitted the report for pre-review, which was approved.
• Ovarian stimulation yielded 12 eggs; after fertilization, 8 blastocysts formed, all biopsied.
• PGT-M results showed: 3 embryos carried the BRCA1 mutation, 5 did not; combined with PGT-A: 2 of the non-carrier embryos were chromosomally normal.
• Transferred 1 embryo, resulting in a successful pregnancy. Amniocentesis at 18 weeks confirmed the results matched the embryo testing.

Two key points in this case: First, although the mother had passed away, the probe design issue was resolved using the father's sample and haplotype analysis. Second, the AMH was at a borderline level, and the number of eggs retrieved was acceptable, but if AMH were lower, two ovarian stimulation cycles might have been needed.

Handling Special Situations

• Proband Deceased, No DNA Sample Available: Haplotyping can be done using samples from parents or children, but success depends on the mutation type and family structure. In some cases, probe design may not be possible, requiring consultation with a genetic laboratory.
• Detection of a Variant of Uncertain Significance (VUS): If the genetic test report shows a VUS rather than a clear pathogenic mutation, PGT-M usually cannot be performed. It may be necessary to wait for future research reclassification or use other testing methods.
• Severely Diminished Ovarian Function (AMH < 0.5 ng/mL): It is recommended to first consider fertility preservation (egg or embryo freezing), or consider an egg donation + PGT-M model (where the donor does not carry the mutation).
• Male Carrying the Pathogenic Gene: The process is similar. A male carrier does not affect the number of eggs, but a semen analysis is needed. If sperm quality is normal, the PGT-M process is the same as for a female carrier, except that ovarian stimulation and egg retrieval are performed on the female partner.

Frequently Asked Questions

• Q: What materials are needed for PGT-M in Thailand?
  A: ID cards and passports for you and your spouse; a complete genetic counseling report and genetic testing report (English version); the proband's medical records and genetic report (if available); fertility test reports from the last 3 months (AMH, FSH, vaginal ultrasound, semen analysis).
• Q: How many trips to Thailand are needed for the entire process?
  A: At least 2 trips. The first for initial consultation + ovarian stimulation + egg retrieval (about 2 weeks), the second for frozen embryo transfer (about 2 weeks). If remote pre-review is chosen, one trip may be saved.
• Q: How long does it take to get PGT-M results?
  A: Generally 2-4 weeks, depending on the laboratory's schedule and the complexity of the testing protocol.
• Q: Are the test results accurate?
  A: The accuracy for single gene testing is between 97-99%, but there are risks of allele dropout (ADO) and mosaicism. Prenatal diagnosis (chorionic villus sampling or amniocentesis) is recommended after transfer for confirmation.
• Q: Which Thai fertility centers can perform PGT-M for hereditary cancer?
  A: Some large Thai fertility centers have dedicated genetics departments, such as BNH Hospital, Phyathai 2 Hospital, and Jetanin Hospital. It is advisable to contact the center directly to confirm their experience with specific gene sites.