MR guided high intensity focused ultrasound (MRgHIFU) for treating recurrent gynaecological tumours: a pilot feasibility study

Abstract

Objective: To assess the feasibility of targeting recurrent gynaecological tumours with MR guided high intensity focused ultrasound (MRgHIFU). Methods: 20 patients with recurrent gynaecological tumours were prospectively scanned on a Philips/Profound 3 T Achieva MR/ Sonalleve HIFU system. Gross tumour volume (GTV) and planning target volume (PTV) were delineated on T 2W and diffusion-weighted imaging (DWI). Achievable treatment volumes that (i) assumed bowel and/or urogenital tract preparation could be used to reduce risk of damage to organs-at-risk (TVoptimal), or (ii) assumed no preparations were possible (TVno-prep) were compared with PTV on virtual treatment plans. Patients were considered treatable if TVoptimal ≥ 50 % PTV. Results: 11/20 patients (55%) were treatable if preparation strategies were used: nine had central pelvic recurrences, two had tumours in metastatic locations. Treatable volume ranged from 3.4 to 90.3 ml, representing 70 ± 17 % of PTVs. Without preparation, 6/20 (30%) patients were treatable (four central recurrences, two metastatic lesions). Limiting factors were disease beyond reach of the HIFU transducer, and bone obstructing tumour access. DWI assisted tumour outlining, but differences from T 2W imaging in GTV size (16.9 ± 23.0%) and PTV location (3.8 ± 2.8 mm in phase-encode direction) limited its use for treatment planning. Conclusions: Despite variation in size and location within the pelvis, ≥ 50 % of tumour volumes were considered targetable in 55 % patients while avoiding adjacent critical structures. A prospective treatment study will assess safety and symptom relief in a second patient cohort. Advances in knowledge: Target size, location and access make MRgHIFU a viable treatment modality for treating symptomatic recurrent gynaecological tumours within the pelvis.

Prediction of pelvic tumour coverage by magnetic resonance-guided high-intensity focused ultrasound (MRgHIFU) from referral imaging

“…Magnetic resonance guided high-intensity focused ultrasound (MRgHIFU) is a noninvasive, non-ionizing treatment modality which has a number of established clinical applications including the ablation of uterine fibroids and bone nerves (for pain palliation) [1], and the treatment of essential tremor [2]. In addition, MRgHIFU is being trialed in the UK for the thermal ablation of recurrent gynaecological tumors (NCT02714621) [3].…”

“…MRgHIFU therapy of pelvic tumors is particularly challenging because of the depth of the tumors within the body. MRgHIFU systems can only treat targets within the focal length constraints of their transducers, and identifying acoustic access which is free from obstruction by acoustically opaque tissues, such as gas and bone, and from organs at risk is challenging [3]. Failure to correctly identify suitable patients for MRgHIFU therapy could deprive them of their only treatment option, while failure to identify patients who cannot be treated wastes patient time and hospital resources on screening sessions.…”

“…Currently, the clinical evaluation process relies heavily on experience and opinion. The process is as follows: patients are referred to the MRgHIFU clinic on the basis of supine diagnostic imaging, often follow-up imaging after unsuccessful prior treatment [3,4] and referred to here as the 'referral image dataset'. If at this point treatment appears qualitatively feasible, patients progress to the screening stage.…”

“…In a previous metastatic bone pain palliation trial, 16 of 37 patients (43%) initially considered for treatment were found at screening not to satisfy eligibility criteria because of disease that could not be targeted, for reasons that include tumor accessibility and size [4]. In a pilot planning study which assessed MRgHIFU for the treatment of recurrent gynaecological tumors, 9 of 20 eligible patients (45%) who underwent screening imaging were subsequently assessed as untreatable because of an eligibility criterion, namely, that >50% tumor coverage could be achieved without risk of damage to surrounding structures [3]. These two studies suggest that, for abdominal pelvic tumors, the current evaluation process may overestimate the number of patients that are suitable for MRgHIFU by more than 40%.…”

Increased Tissue Penetration of Doxorubicin in Pressurized Intraperitoneal Aerosol Chemotherapy (PIPAC) after High-Intensity Ultrasound (HIUS)

“…In this regard, high intensity ultrasound (HIUS) has been a very promising method to potentially achieve this goal. HIUS has been investigated for over two decades in solid tumor therapy with promising results in particular cases [18][19][20]. It is already known that HIUS can improve the perfusion of chemotherapy agents in liver tumors and glioblastoma [21,22].…”