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Transrectal high‐intensity focused ultrasound as focal therapy for posterior deep infiltrating endometriosis

2017; Wiley; Volume: 51; Issue: 1 Linguagem: Inglês

10.1002/uog.17497

1469-0705

Gil Dubernard, A. Gelet, Cyril Lafon, Nicolas Guillen, F. Chavrier, J. Y. Chapelon, C. Huissoud, Charles-André Philip,

Endometrial and Cervical Cancer Treatments

Posterior deep infiltrating endometriosis (DIE) is one of the most common forms of the condition1. The rectosigmoid colon is often involved and can be associated with symptoms such as diarrhea, dyschezia and bowel cramping. As medical treatments are often not curative, surgical procedures are frequently required. When an endometriotic lesion infiltrates the rectosigmoid colon, a colorectal resection is performed in 71% of cases1. This surgery, usually performed by laparoscopy, is often lengthy and complex, and a digestive derivation is often required to prevent postoperative complications including rectovaginal fistulae2. Several long-term side effects, such as dysuria and digestive dysfunction, are frequently observed following surgery3, 4. High-intensity focused ultrasound (HIFU) is currently being used to treat various malignant tumors, myomas and adenomyosis5. It is a non-invasive ablative procedure using an external ultrasound source to induce remotely acoustic cavitation and thermal ablation of tissue. Using our exposure conditions, a reproducible, small volume of ablated tissue, corresponding to a focal zone of –6 db (estimated to be 3.7 mm3, i.e. 0.58 mm in longitudinal diameter, 1 mm in transverse diameter and 6.4 mm in acoustic axis), is created for each pulse of energy. The risk of fistulae in prostate cancer treated with HIFU is estimated to be 0.13%6 and is lower than the risk of 1.6–2.8% reported in the surgical management of rectal DIE7. Focal One® (EDAP-TMS, Vaulx-en-Velin, France) is a transrectal HIFU device validated for the treatment of localized prostate cancer. The endorectal dynamic focusing probe is composed of two ultrasonic transducers, a HIFU transducer and imaging transducer, to allow visualization of the target region. The imaging transducer is embedded in the center of the therapeutic transducer enabling alignment of the transverse imaging plane with the HIFU focal area. The HIFU source is a spherical annular array composed of 16 isocentric rings. Procedures using Focal One® are performed under local anesthesia. The probe is introduced into the rectum while real-time guided ultrasonography is used to determine the location of the endometriotic nodule. The volume of the target area is then drawn on the Focal One® screen, including a safety margin of 3 mm for the digestive mucosae, to prevent the risk of fistula formation. The focal points are positioned automatically by the software (Figure 1) and the target area divided into several sections from the higher to the lower limits of the lesion with one section every 1.7 mm. The focal distance is electronically steered along the acoustic axis without any mechanical movement. Each HIFU exposure performed at a given focal distance, in this case 32 and 37 mm (Figure 1), lasts 1 second with no pause in between. Their distribution within one slice depends directly on the size and shape of the endometriotic nodule. From the five patients included in this study, an average of 6 (range, 5–7) sections were defined. The range of the acoustic output power was regulated from 4.7 to 42.3 W according to the focal distances used during the procedure and led to an acoustic intensity ranging from 673 to 7650 W/cm2 in water. Whilst the attenuation of the endometriotic nodule is not precisely known, assuming that it is similar to the attenuation of prostatic tissue (9 Np/m/MHz), it led to an acoustic intensity ranging from 413 to 3592 W/cm2. This intensity corresponds to 50% of that used for the prostate, which was in order to favor safety over efficacy in this feasibility study. The median volume of the endometriotic lesion was 0.8 cm3 and so the median duration of the procedure was only 90 (range, 88–172) seconds. The median hospital stay was two nights and the median period of follow-up was 6.7 (range, 3–10) months, with no complications occurring during or after the procedures. Conventional B-mode and contrast enhanced ultrasound imaging with Sonovue® were used before and after each procedure to assess the effect of the HIFU on the endometriotic tissue. Objective evidence of tissue effect was observed in only one case in which increased acoustic attenuation of the nodule and decreased perfusion were observed. Although the one instance of an overall decrease in nodule size observed from postoperative magnetic resonance imaging and transvaginal ultrasound scans was not significant, after 3 months there was a trend towards an improvement in pelvic pain measured on the visual analog scale with a 2.55-mm reduction (SD = 1.59, P = 0.05) as well as a Medical Outcomes Study 36-item short-form quality of life score increase of 23.95% (SD = 23.9%, P = 0.14). In this preliminary study we assessed the feasibility of ultrasound-guided HIFU ablation of posterior DIE with digestive involvement. As four out of five of the procedures were completed and no adverse event occurred, HIFU therapy could be considered as a feasible alternative to surgery. Further studies are required to confirm these preliminary results and assess the effectiveness of the procedure. To this end, we are currently conducting a single-center prospective clinical study to assess the feasibility, safety and efficacy of Focal One® on patients presenting with posterior DIE and rectosigmoid involvement. The study was approved by the French Agency for the Safety of Health Products (ANSM) and local ethics committee, Le Comité de Protection des Personnes (CPP SUD-EST II). Dr A. Gelet is an investigator for EDAP TMS company researching HIFU for prostate cancer. Dr N Guillen was an employee of EDAP TMS, during the conduct of the study. Dr C. Lafon received grants from EDAP TMS, during the conduct of the study.