Resolution of a septated pancreatic cyst by booster endoscopic ultrasonography‐guided ablation

Management of pancreatic cyst is challenging as most of them are asymptomatic but may have malignant potential, and surgical resection has a substantial risk.1,2 The management strategy should therefore be individualized by a risk-benefit analysis for each patient.3 Recently, endoscopic ultrasonography (EUS)-guided pancreatic cyst ablation has been tried with ethanol lavage alone or ethanol lavage with additional injection of a chemotherapeutic agent.4,5 An EUS-guided cyst ablation is a minimally invasive and promising therapeutic option, but cyst resolution after ablative therapy still needs to be improved. The presence of septa in a cyst may increase the surface area to be ablated and thus deter effective ablation.6 Procedural innovations such as booster ablation or retention of ethanol in the cyst cavity rather than aspiration may improve therapeutic efficacy, especially in large septated cysts. In this case report, a large, septated pancreatic cyst was treated with two sessions during the first ablation and a third session during the second ablation 23 months apart, and showed near complete resolution. This case study highlights the sequential morphological changes after a cyst ablation and its effectiveness for booster ablation. A 38-year-old woman was referred for a 7-cm sized pancreatic cyst detected on transabdominal ultrasonography during a health maintenance examination. She had complained of vague abdominal discomfort without symptoms of bowel obstruction. Computed tomography (CT) and EUS showed a 68 mm × 53 mm septated cyst in the pancreatic head with a wall thickness of 3 mm (Fig. 1a,b) and a computer calculated cyst volume of 68.74 mL. Surgical resection was considered due to its large size and the possibility of obstruction symptoms, but the patient declined and decided to undergo EUS-guided cyst ablation. A prophylactic antibiotic was administered i.v. prior to the procedure. Under guidance of a curvilinear-array echoendoscope (GF-UCT240-AL5; Olympus Optical Co, Tokyo, Japan), the cystic lesion was punctured with a 22 gauge needle (EchoTip Ultra; Wilson-Cook Medical, NC, USA). Only 10 mL of cyst fluid was aspirated. Then 15 mL of 99% ethanol was injected into the cyst and lavage (repeated injection and aspiration) was performed for 5 min. After aspiration of lavage fluid, 4 mL (12 mg) of paclitaxel solution (diluted 1:1 in 0.9% normal saline and prepared in a dose concentration of 3 mg/mL because of high viscosity; Taxol, Bristol-Myers Squibb Pharmaceutical Group, Montreal, Canada) was injected into the cyst cavity. Given that the first needle pass failed to puncture all locules and only a small amount of cyst fluid was aspirated from a large estimated cyst volume, a second needle pass through a different angle was performed. In this second session, 6 mL of cyst fluid was aspirated, ethanol lavage (12 mL) was done, and 4 mL of paclitaxel solution was injected. The cyst fluid carcinoembryonic antigen (CEA) and amylase levels were 1 ng/mL and 118 U/L, respectively. Cyst fluid cytology was negative. A diagnosis of oligocystic serous cystadenoma was presumed by cyst morphology and fluid analysis. Follow-up CT 4 months after the ablation showed that the cyst diameter and volume had decreased to 35 mm and 17.92 mL, respectively. Septa discernible on the initial CT scan were no longer visible (Fig. 1c). On serial CT scans at 7, 14 and 20 months after ablation, cyst volumes were 12.30 mL, 6.71 mL and 7.57 mL, respectively. On the last CT scan, cyst regrowth was suspected as the cyst volume had increased and an eccentrically located septum was discernible (Fig. 1d). The cyst was multilocular, measuring 28 mm × 25 mm with a wall thickness of approximately 5 mm (Fig. 1e). A third session at this second ablation was performed to achieve the complete resolution at 23 months after the first procedure. Under EUS guidance, 5 mL of cyst fluid was aspirated by the first needle pass into one dominant locule and ethanol lavage was done. After reposition of needle into another locule, cyst fluid aspiration and ethanol lavage were done. Then 5 mL (30 mg) of undiluted paclitaxel formula (Genexol-PM [polymeric micelle], Samyang, Seoul, Korea) was injected. A higher dosage of paclitaxel was used because the cyst wall was thick and the low viscosity of this formula allowed for easy injection. A follow-up CT 5 months later showed an estimated cyst volume of 7.42 mL, similar to the volume just before the second ablation. On an 11-month follow-up CT, the cyst volume had decreased to 1.06 mL from 68.74 mL of initial volume (Fig. 1f) and a 5-mm thick cyst wall was clearly discernible. Given the lack of complete resolution, regular follow-ups will be required. A repeat CT was scheduled for 6 months later. Computed tomography (CT) and endoscopic ultrasonography (EUS) show (a, b) a 68 mm × 53 mm septated cyst in the pancreatic head with a wall thickness of 3 mm. (c) A follow-up CT after 4 months shows that cyst volume had decreased to 17.92 mL and the septa discernible on initial CT had resolved. (d) Follow-up CT at 20 months shows suspected cyst regrowth. (e) EUS at the second ablation shows a 28 mm × 25 mm septated cyst with a wall thickness up to 5 mm. (f) On follow-up CT 11 months after the second ablation, the cyst volume had decreased to 1.06 mL from the initial 68.74 mL. Our proposed indications for an EUS-guided cyst ablation are now strictly confined to benign-looking indeterminate cysts that are not discriminated by conventional imaging and for which EUS-guided fine needle aspiration is considered for additional information. From the viewpoint of cyst morphology, cysts that have few locules (arbitrarily six or fewer) are preferably indicated, as the presence of septa may prevent the delivery of the ablation agent into all locules.5,6 To minimize the possibility of missed locules, the needle pass must be planned according to the cyst's internal structure. Multiple needle passes through different angles may probably increase not only the effectiveness of the cyst ablation but also the risk of complications. Therefore, a second needle pass may be considered in the same session of cyst ablation when it can be performed without increasing the risk of complications in technical aspects. In the published studies, complete resolution was achieved in 35%,4 3%7 and 62%8 of patients, respectively, and EUS-guided cyst ablation was performed safely without serious complications. Complete cyst resolution was achieved between 6 and 12 months after cyst ablation in half of these cases, and cyst regrowth after a good initial response by 6 months was observed.8 Imaging follow-ups are required at 3-month to 6-month intervals based on the initial treatment response. Booster ablation is another procedural invention that may improve cyst resolution, as repeated contact with the ablation agent is likely to increase its effect.7 Booster ablation may be considered when (i) a large cyst shows a plateau in treatment response after the first ablation and cyst size is still compatible for cyst ablation (>2–3 cm); or (ii) septa are persistently observed or newly discernible on follow-up imaging and cyst regrowth from a missed locule is suspected. In summary, EUS-guided pancreatic cyst ablation may be an effective treatment option. In addition, tailored intervention according to the internal structure of cyst is required to improve the treatment response and booster ablation should be considered when complete resolution is predicted by the initial response and an additional ablation can be safely performed.

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