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