Re-evaluating PGT-A:

current thoughts and controversies

Sesh K Sunkara MBBS, MD, MRCOG

King’s College London

London, UKThe views expressed in this presentation are those of the presenter and do not necessarily reflect the views of Merck. This presentation is for medical education purposes only

Outline

• Rationale for PGT-A/ PGS

• Evolution from PGS 1:0 to 2:0

• Who could benefit from PGT-A?

• What are the outcomes for assessing

effectiveness of PGT-A?

• Current evidence and conclusions

Human fecundability

• Human conception is considerably inefficient

• Fecundity rate ~ 40% per menstrual cycle (Wang et al., Fertil Steril 2003)

• Chance of recognised clinical pregnancy ~30% per menstrual cycle

(Macklon et al., Hum Reprod Update 2002)

• Extensive loss of early conceptions - pre clinical, clinical

• Embryo aneuploidy major reason for failed conceptions and

pregnancy losses

Improving ART efficiency

• Aneuploidy also a barrier to ART efficiency (Rabinowitz et al., Fertil Steril 2012; Fragouli et al., Hum Genet 2013)

• PGS based on the hypothesis that selection of euploid oocytes,

embryos lead to improved ART outcomes (Munne et al., Human Reprod 1993)

• Introduced in the early 1990s

• Evolution from PGS 1:0 to PGS 2:0

• Newer concepts of non-invasive preimplantation genetic testing (NIPT)

PGS 1:0

Adapted from Geraedts and Sermon. Hum Reprod 2016

• Widely applied for ~15 years

Mastenbroek et al., 2007

• Multi-centre RCT, 3 cycles of IVF with or without PGS, women 35-41 yrs

• 206 women in PGS arm (day 3 biopsy and FISH) vs 202 in control arm

• OPR significantly lower in PGS arm 25% (52/206) vs 37% (74/202)

• LBR significantly lower in PGS arm 24%% vs 35%

PGS did not increase but instead significantly decreased ongoing pregnancy and live birth rates in women of advanced reproductive age

Mastenbroek et al., 2011

• All studies except Jansen et al.,

2008 had blastomere biopsy

• All studies had FISH analysis

Policy statements issued stated

no evidence to support routine

clinical use of PGS

ASRM

ESHRE

• Cleavage stage biopsy detrimental to

embryo

• Incomplete chromosomal assessment with

FISH

• Higher levels of mosaicism in day 3

embryos

• Self-correction of mosaicism

Why is PGS 1:0 ineffective,

detrimental?

PGS 2:0

Adapted from Geraedts and Sermon. Hum Reprod 2016

qPCR quantitative polymerase chain reactionWGA whole genome amplificationm-CGH metaphase comparative genomic hybridisationa-CGH array CGH

SNP single nucleotide polymorphismMPS multiple parallel sequencing

Resurgence of PGS

Schoolcraft et al., ASRM 2012

1st RCT with PGS 2:0

• Infertile women aged > 35 years

• Randomised at oocyte retrieval to fresh blastocyst transfer following

morphological selection (n=30) vs PGS arm – trophectoderm biopsy,

CCS with SNP microarray, vitrification, FET (n=30)

• Viable implantation rate was significantly higher in PGS arm (60.8% vs

40.9%)

• Miscarriage rate was significantly lower in PGS arm (0% vs 20%)

All women had D6 fresh transfers

Forman et al., Fertil Steril 2013

• Determine if PGS and SET can achieve

comparable OPR whilst reducing multiple

gestation compared to DET without PGS

• Women aged < 43 years, mean age ~ 35 years

• Randomisation on D5/6 if ≥ 2 expanded

blastocysts

• PCR based CCS, fresh D6 or frozen transfer

Scott et al., Fertil Steril 2013

• Determine if PGS improves IVF implantation and delivery rates

• Women aged < 43 years, mean age ~32 years

• Randomisation on D5 if ≥ 2 blastocysts available

• qPCR based CCS

• Fresh D5 transfer in control arm, D6 fresh transfer in study arm

66.4%

47.9%

84.7%

67.5%

• Excellent outcomes in both groups• PGS further improving outcomes Scott et al., Fertil Steril 2013

Do all centres have such excellent results?

Rubio et al., Fertil Steril 2017

• Determine value of PGS in advanced maternal age women (38-41

years)

• PGS arm had D3 biopsy and CCS with a-CGH

• All women in both arms had fresh blastocyst transfer followed by FET

PGS NO PGS OR (95% CI)

Number of cycles 100 105

Number of cycles with transfer 68 (68%) 95 (90.5%) 0.22 (0.10 – 0.48)

Miscarriages (%) 1 (2.7%) 16 (39%) 0.06 (0.008 – 0.48)

Delivery rate after the first ET 36 (52.9%) 23 (24.2%) 3.52 (1.80 – 6.87)

Delivery rate per patient 36% 21.9% 2.00 (1.08 – 3.71)

Clinical outcome at the first attempt (per transfer and per patient)

• No significant difference in cumulative delivery rate 37% with PGS vs 33.3% in

the control group

• Significantly shorter TTP with PGS and euploid transfer 7.7 vs 14.9 weeks

Rubio et al., Fertil Steril 2017

2016

Likewise, no common denominator in RCTs evaluating PGS 2:0

Dahdouh et al., Fertil Steril 2015

Main outcome:IR

2016

• IR is of interest to an embryologist BUT

• Is not a measure of IVF effectiveness

• Unit of randomisation, denominator has to be women NOT embryos

• Largest RCT, 650 women randomised• 4 countries, 34 sites, 9 genetic laboratories

Murugappan et al., 2016

Retrospective cohort analysis

CM = clinical miscarriage

Greco et al., NEJM 2015

• 3802 blastocysts analysed by a-CGH between May 2013-July 2014

• Chromosomal mosaicism detected in 181 (4.8%) blastocysts

• 18 women with no euploid embryos counselled to have transfer of

mosaic blastocyst

• 8 clinical pregnancies and 6 term singleton live births

• All had normal karyotype

Mosaicism

• Not all embryonic cells share identical

chromosomal complements despite originating

from same zygote

• Mitotic errors result in chromosomally distinct cell

populations, diploid and aneuploid cell lines

• Lower levels of aneuploidy with increasing

gestational age

• Likely mechanism “aneuploidy correction” or

mechanism by which aneuploid cells

“outcompeted” by euploid cells

Types of blastocyst mosaicism

Vera-Rodriguez and Rubio. Fertil Steril 2017

Clinical outcomes of live births from mosaic embryos have wide phenotypes

Healthy to severely impaired

Sermon et al., 2016

• Clear on definition of PGS 2:0

• Blastocyst stage biopsy, CCS, possible vitrification

• Agreed mosaicism less of an issue at blastocyst over cleavage stage

• Whether mosaicism is an issue at blastocyst stage is currently called into

question

CURRENT THOUGHTS

The why?

Which patient groups is PGS indicated?

• Recurrent implantation failure (RIF)

• Repeated miscarriages

• Advanced maternal age (AMA)

• Young and good prognosis patients

• All patients undergoing IVF

• Egg donor cycles

• No indications for PGS

Sermon et al., Hum Reprod 2016

What is success?

• Live birth

• Reduce time to pregnancy (TTP)

• Reduce miscarriages

• Reduce multiple births

• Reduce live births with aneuploidy

• Cumulative live birth rate?

Sermon et al., Hum Reprod 2016

The how?

• Which amplification method?

• WGA

• qPCR

• Which method for CCS?

• a-CGH

• SNP

• Next generation sequencing (NGS)

• Targeted NGS

Sermon et al., Hum Reprod 2016

Other comments

• Use PGS to rank embryos based on

implantation potential

• Detection levels vary between technologies and

laboratories

• True clinical significance of aneuploidy unclear

• Caution as PGS still shows false +ves and false

-ves

Sermon et al., Hum Reprod 2016

Conclusion

• Informed and shared decision making between clinicians and patients

• Understand patient expectations

• Explain current evidence, uncertainties, equipoise and costs

• Need for robust RCT

• Several suggested indications, outcomes of interest

• Justify PICO

• Denominator, point of randomisation should be credible

Thank you