Discussion:
The current review appraises HIFU as a new conservative management of
PAS. For decades, HIFU has been recognized as an intervention for
various benign and malignant solid tumors including benign uterine
lesions. However, it has been recently studied in women with PAS who are
highly motivated to avoid hysterectomy. Preliminary results on 399
patients convey high success rate and reassuring safety profile. The
incidence of complications was less than 1%.
Although HIFU seems to be more effective and safer compared to other
uterus-conserving procedures, selection criteria of included studies,
which are substantially consistent, may limit indications of treatment.
Eligible patients should be clinically stable with no active bleeding,
and residual placenta should be larger than 3 cm, yet not occupying more
than half of the uterine cavity (19). Therefore, HIFU may be a favorable
option in patients who were not diagnosed antenatally, including women
who underwent vaginal delivery with incomplete separation of the
placenta. Despite advancement in prenatal diagnostic modalities,
antenatal diagnosis may be missed in 47% of women with PAS, and they
are at greater risk of hemorrhagic morbidity (22). In this set of
patients, HIFU may substitute other conservative procedures, that may be
associated with higher risk of intraoperative and postoperative
complications (Table S3). In women with antenatally planned conservative
management, HIFU is unlikely to serve as a sole intervention unless
further studies confirm its capacity to ablate a complete placenta with
no significant complications. In the meanwhile, it may be reasonable to
consider HIFU as a backup intervention in women managed by other
conservative options particularly in clinically stable patients.
Although several uterus-conserving interventions have been proposed in
management of PAS, their contribution to evidence-based practice is
limited (23), and cesarean hysterectomy is endorsed as the standard
intervention (24). Cesarean hysterectomy, without attempting to remove
the placenta, may reduce risk of significant bleeding and associated
morbidity (25). Leaving the placenta in situ is endorsed as an
alternative in patients who refuse hysterectomy being the least invasive
uterus-conserving intervention (11, 23).
Nevertheless, the need for evidence-based conservative approaches for
PAS cannot be underestimated particularly among women who are highly
motivated to preserve their fertility. Despite limited evidence, an
international survey indicates that 39% of obstetricians consider
conservative management as the primary management. Notably, conservative
management was inconsistent among respondents (1). Sixty-one articles
were retrieved from our CON-PAS registry on conservative management
using UAE (23 studies) (26-48), prophylactic balloon placement (15
studies) (49-63), compression sutures (10 studies) (64-73), leaving
placenta in situ (7 studies) (74-80), and uterine wall excision and
reconstruction (6 studies) (81-86). Despite the number of conducted
studies (61 studies, 1,979 patients), they have not yielded robust
evidence-based recommendations. Fifty-four and eighty-nine percent of
these studies recruited ≤ 20 patients and ≤ 50 patients, respectively.
Most of these studies are either retrospective or case series, and they
tend to describe a surgical technique rather than a patient-based
comprehensive protocol. Therefore, determining optimal candidates for
these techniques may not be clear.
Although these limitations may be attributed to relative paucity of
patients with PAS, geographic distribution of these studies is limited
to 17 countries; 54% of them were conducted in China (20 studies),
France (7 studies) and Egypt (6 studies) (Figure 3). This raises
concerns about amount of missed data from the rest of the world, which
would have contributed to clinical evidence of this uncommon disorder. A
stepwise research approach may optimize utilization of available data
and enhance generalizability of results. This may include conducting
international multicenter retrospective studies to secure large data for
analysis, thereby promoting assessment of clinical outcomes of different
interventions/steps according to patient and disease characteristics.
Results from these data would facilitate delineation of safe prospective
studies and clinical trials that incorporate conservative management as
a part of a comprehensive protocol for all clinical scenarios of PAS. As
a part of this approach, an international multicenter retrospective
study is currently taking place in 11 medical centers from Europe, Asia,
and Africa (clinicaltrials.gov ID: NCT04384510 ).
The current review presents outcomes of a new modality of conservative
management of PAS, which seems to yield promising results. In addition,
it highlights restrictions of converting uterus-preserving studies into
evidence-based recommendations despite the wide adoption of this
practice. This review is limited by the retrospective nature of included
studies. Furthermore, role of HIFU in women with prenatally diagnosed
PAS is not well defined, and further studies may be warranted to
incorporate this procedure in a PAS management protocol.
In conclusion, HIFU is a promising treatment modality particularly when
diagnosis of PAS is made intrapartum without significant uterine
bleeding. A global research strategy may be warranted to support such
modalities as a part of evidence-based protocol in management of PAS who
are highly motivated to preserve their fertility.
Acknowledgements: none
Disclosure of Interests: The authors have no conflicts of
interest. No financial disclosure to declare