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NEW ORLEANS -- Almost 40% of diabetes patients who used a hybrid closed-loop insulin delivery system to improve glucose control quit the system within a few months, researchers reported here.

In a real-world, observational study of 93 pediatric and young adults patients with type 1 diabetes from a single clinic, 38% (n=35) discontinued use of the system within 9 months, according to Gregory Goodwin, MD, of Boston Children's Hospital, and colleagues.

The reason for this high discontinuation rate was often due to trouble staying in automode -- referred to as the true "artificial pancreas" -- Goodwin explained at ENDO 2019, The Endocrine Society annual meeting.

Other reasons for discontinuation included technical difficulties with use of the system, such as frequent alarms, premature sensor failure, requirement of calibration, skin adhesion problems, and sensor supply issues.

"Theoretically it's brilliant," Goodwin commented about the closed-loop system, but referenced the lack of real-world data to mirror the success the system has seen with tightening time spent in range in a trial setting.

The patients (age range 6-25 years) freely chose to use the Medtronic MiniMed 670G hybrid closed loop insulin pump, which was approved as the first artificial pancreas system for patients, ages ≥14 years, in 2016. In 2018, the FDA expanded the indication for the system to include patients, ages ≥7 years. The pump was paired with the Guardian 3 sensor, and most of the patients wore it on their abdomen, although it was cleared by the FDA for placement on the upper arm last year.

"We actually used [this system] in a 5-year-old. It's up to the discretion of the treating physician," Goodwin told 番茄社区app, adding "I would not use it in [a patient younger] than a 5-year-old."

Among 62% (n=58) of the study patients who continued to use the system throughout the average 8-month follow-up period, the percentage of time spent in automode varied greatly, ranging from only 10% of the time up to 90% of the time.

For the 58 participants that stuck with the system in automode for some portion of time, and had available HbA1c numbers, a significant decrease in HbA1c was seen after 6 months compared with baseline A1c concentrations. However, beyond this 6-month mark, HbA1c concentration started to rise, and was no longer significantly lower than baseline readings:

• Mean baseline HbA1c: 7.97
• 0-6 months: mean decrease of 0.27 (P=0.02)
• 6-12 months: decrease of 0.18 (P=0.16)
• 12-24 months: decrease of 0.03 (P=0.88)

Not surprisingly, the percentage of time spent in automode was correlated with average HbA1c levels, with the lowest levels seen among patients who spent 57%-74% of time and >74% of the time in automode (A1c from 7.5-8 for both groups). Those who only spent <35% of the time in automode averaged an A1c of around 8.4.

In order to make the system more user-friendly and increase compliance, Goodwin suggested during an ENDO press conference that there must be a decrease in the frequency of alarms and in the frequency of exits from automode. "It's just too demanding on the patients," he said, adding that "in order to be successful at this, it's really a full-time job to keep yourself in target."

These improvements may not be too far off in the future either, Goodwin told 番茄社区app. Updates to the MiniMed 670G system have been made since the study, including a new transmitter that sends sensor information to the insulin pump and a software enhancement that removes the safety check for a continuous blood glucose entry request in some instances. For patients that struggle with the system, he said he would first recommend patients try the updated system before giving up on the closed-loop system.

"I do think the hybrid closed-loop insulin delivery system is the future. This is the first generation; it will improve with time. I would encourage them to stay with the system, but I really go with what [patients] want ... we need better systems," he said.

Anders Carlson, MD, of the International Diabetes Center in Minneapolis, agreed that automated insulin delivery is the future. "Of course, sensors need to get better, integration of devices with each other, and perhaps how they can be interoperable will be a major step forward," he said at the press conference.

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