How to evaluate success with PGS

Don Leigh

ASPIRE April 2014

• ~2/3 of clinical miscarriages are caused by chromosome aneuploidy• Some aneuploidies are not observed in miscarriages and believed to be

implantation/development lethal • IVF implantation rates decrease with increasing age• IVF embryos show variable aneuploidy rates (5-70% age related)• Natural pregnancies show an age related increase in incidence of trisomy 21

PGS should provide an opportunity to improve the success of an embryo transfer

Transfers have emotional, time and monetary costs Implantation failures and miscarriages have high emotional cost, larger time costs, health costs and

significant monetary costs

IVF . . . What can be done to improve things?

It is a logical conclusion that identifying and avoiding the transfer of aneuploid embryos will change the implantation rates and also the miscarriage rates

Randomised Trials

• Sizes: 60-~400 patients

• Biopsy stage: 8x blastomere (1/2 cells), 1x blastocyst

• Prognosis group: AMA (5), Good (3), RIF (1)

• Outcomes Implantation rates: Control 7%-60% Test 14%-56%

Miscarriage rates: Control 4%-38% Test 20%-70%

Why the question about PGS efficacy?

Mastenbroek et al 2011

• Aneuploid embryos were identified and excluded but most results were poorer

The simplest conclusion was that PGS is in fact detrimental to transfer outcomes . . .!!

What did PGS offer?

X

X

X

X

• ESHRE data XI Implantation rate: 13%-35% ave. 22%

Miscarriage rate: 6%-39% ave. 16%

• Polar Body (RGI) Implantation rate: ~32%

Miscarriage rate: decreased

• Literature Implantation rate: 20%-35%

Miscarriage rate: <10%

PGS back then . . . . .

FISH- 5c, 7c, 9c

The arguments back then . . .

• Poor Biopsy technique Poor biopsy technique damages the embryo

– 1 blastomere- development stage sometimes not appropriate

– 2 blastomeres- reported already as detrimental

• Poor analysis Poor technique

– High analysis failure rate indicative of poor lab practices

Wrong screening set used– 5-9 chromosomes tested- but these are not the most prevalent

aneuploidies observed in embryos (35-60% coverage)

• Mosaicism Cleavage stage embryos often mosaic. Wrong identification and

exclusion. Loss of good cells leaving poorer embryo. Rejection of good embryos

• Polar Body Technically the most challenging (good technique essential)

Debate on whether it is inclusive enough to identify sufficient aneuploidies

• Day 3 Mosaicism may be relevant (but realistically how relevant?)

Some technical challenges (good technique important)

• Day 5 Need extended culture (not difficult in a good lab)

Technically straight forward

Time needed for analysis- freezing?

A laboratory process can have a major impact on success

• Wells et al 2008 Implantation failure patients

Day 5 trophectoderm biopsy

Vitrified embryos

CGH 24 chromosome screen

Finally . . Total chromosome screen

Implantation rates approached 70%

A breakthrough . . .?

• Now all gross chromosome abnormalities were identifiable- including those aneuploidies leading to implantation failure and miscarriage

typically 40% to 70% of embryos are aneuploid and should not be used

• Now more and more studies report similar positive implantation rate changes after PGS

• But Wells’ group also did D5 biopsy Frozen cycles

Were these the important differences?

PGS now . . . .

Stage of biopsy . . . .

0%

10%

20%

30%

40%

50%

60%

day 3 biopsy day 5 biopsy

control

biopsy

Treff et al 2011

Screening must improve outcomes >60% just to overcome impact of biopsy

• Patient

• Clinician

• Laboratory

• Clinic (Finance, marketing, . . . )

To measure Success- the interested parties . . .

• Patients come to the clinic for many reasons– Subfertility

Implantation failure, miscarriage

– Advanced maternal age– Monogene disorder/translocation– Recurrent miscarriage

• patients just want a pregnancy– A continuing pregnancy

This will not be achieved for some patients

– Actually, the patient actually wants a baby A healthy baby

– Possibly babies- healthy babies- this will not be achieved for a significant number of patients

Success- for the patient

• Good stimulation

–Good eggs (cannot get a good embryo from a bad egg)

Good embryos

–A transfer (uterine receptivity)

»A pregnancy

• A healthy baby

•A happy patient

Success- for the clinician

• Need good eggs–Good embryos (fert*, culture*)

Biopsy*/analysis*

–Transfer (or freeze*)

»Pregnancy

•Healthy baby

Success- for the Lab

PGS does not make any embryo better- it is only a tool to facilitate embryo choice to avoid a significant source of biological negatives

• At best, the laboratory maintains the vitality of an embryo . . . or in a poorly operating clinic makes it worse

• PGS does not improve the patient factors (eg uterine receptivity)

• PGS should not be thought of as the best way to improve a clinic’s outcomes

Implantation rate is a key lab performance indicator- general fresh and frozen implantation rates show how a clinic is performing

In some cases, lab improvements may be the best approach to give the improvements that a clinic is after (Beyer et al 2008)

The caveats . . . .

Performed correctly, PGS

• Improves implantation rates for some (most?) patients– Decreases the futile transfers for most patient types (young,

AMA, recurrent implantation failure*, miscarriage*, tl) by avoiding transfer of unfit embryos

• Decreases miscarriage rates– Minimises miscarriage especially for AMA and tl carriers (but

only aneuploid related miscarriages)

• Can offer single embryo transfer cycles as a real option– Without losing pregnancy rates– Double embryo transfers and the risks associated with multiple

gestations can be a thing of the past

PGS can be a positive

-ve factors

• Poor stimulation

• Poor embryology- biopsied embryos show greater sensitivity to lab conditions

• Biopsy- poor technique has greater negative impact

• Biopsy timing- different costs at different stages

• Poor freezing (fresh = frozen)

• Analysis- poor analysis loses good embryos

• Transfer- fresh vs frozen– Uterine receptivity and state, embryo/uterus synchronicity

What limits successful application of PGS?

• Successful pregnancy is a +/- outcome

– PGS only changes the approach to this outcome.

• Some patients will not achieve a pregnancy

– Not with their own eggs (sperm)

– Not with anyone’s embryos

• Everything we do to an embryo has a negative impact- some big, some small

Other considerations

PGS does work in the right situations- previous failures to show improvements were likely a combination of too many negatives with insufficient positives. Current failures may point to clinic failures

Biopsy may have a larger negative impact on outcome than the positive gain of excluding aneuploid embryos

Different patient groups will see different levels of improvement after PGS- but most will see something

• Some clinics should possibly not be attempting PGS until they improve general lab outcomes

Will PGS offer all clinics success?

When the result/outcome >>

original likely outcome

The final measure of success . . . .

This will occur with PGS when all of the steps from egg through embryo through analysis through transfer/storage are all appropriate and optimal

• PGS offers assistance in identifying the best starting point- it only changes implantation rate– Current form of PGS will improve

More detail ?more improvement in IR?

BUT

• Without better understanding of the patient variables as well, then the approach to a 100% outcome will stall

In the future Preimplantation screening will include both embryo status and patient variables

PGS and its limits

Thank you

• Typically limited exposure to IVF– Primary or secondary infertility

• Often reason for sub-fertility not known– Male factor, female factor, neither, both

• Maybe has tried IVF– Implantation failure– Sub-clinical miscarriages

• Age risk of Down syndrome– Only a few aneuploid syndromes identified- other aneuploidies

result in implantation failure or early loss

• Clinical use- chromosome rearrangements• New type of patient – fertile but a miscarriage history

The Patient

Cannot get a good embryo from a bad egg

• Compromised maturation Other factors (Stimulation type, trigger, etc)

Aneuploidy?

• Number of eggs Low quality? Age related decline in recruitment (AMH)

• Age related aneuploidy increase Base line may reach 60-70% (more if translocation involved)

The clinician

• Egg quality Delivered (Bad eggs, bad embryos)

• Fertilisation Male factors, lab skills

• Culture conditions Impact of compromised laboratory conditions on growth and

development

• Transfer timing Embryo stage

Patient receptivity

Success for the lab