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CHICAGO -- Treatment with tumor treating field (TTFields) therapy combined with standard of care improved overall survival versus standard of care alone in patients with metastatic non-small cell lung cancer (NSCLC) who have progressed on platinum-based therapy, the randomized phase III showed.

At a minimum follow-up of 12 months, the technology -- a device that emits electrical fields with the intent of disrupting cell division -- combined with standard of care increased median overall survival (OS) by 3.3 months compared with standard of care alone (13.2 vs 9.9 months; HR 0.74, 95% CI 0.56-0.98, P=0.035), reported Ticiana Leal, MD, of Emory University's Winship Cancer Institute in Atlanta.

OS rates at 1 and 3 years were 53% and 18%, respectively, with TTFields therapy and 42% and 7% with standard of care -- either immune checkpoint inhibitors (ICIs) or docetaxel.

This improvement in OS was achieved with no significant increase in systemic toxicities, Leal added.

"TTFields therapy should be considered part of standard of care for metastatic non-small cell lung cancer following progression on or after platinum-based therapy," Leal said during a presentation at the American Society of Clinical Oncology (ASCO) annual meeting. "TTFields therapy is a potentially paradigm-shifting new treatment modality."

However, ASCO-invited discussant Rebecca Heist, MD, MPH, of Massachusetts General Hospital in Boston, observed that the changing standard-of-care landscape in NSCLC posed a challenge in this study.

She pointed out that at the time the trial started in 2016, ICIs had already been proven superior to docetaxel in the second-line setting, and that by 2018, ICIs had moved to the first-line. Thus, she said, "we currently do not use ICIs as used in this study."

"I, personally, as a clinician, would always welcome new modalities to treat lung cancer," she noted. "The major caveat, for me, is that the study design does not reflect the current standard of care."

Leal pointed out that "overall survival was particularly prominent in the ICI-treated patients." Specifically, median OS was 18.5 months in the TTFields group and 10.8 months in the standard care arm (HR 0.63, 95% CI 0.41-0.96, P=0.03).

The OS benefit with TTFields was less substantial among patients also treated with docetaxel, with a median OS of 11.1 months versus 8.7 months in those treated with docetaxel alone (HR 0.81, 95% CI 0.55-1.19, P=0.28).

There was no statistically significant difference in progression-free survival (PFS) between the two study arms, with a median PFS of 4.8 months in the TTFields arm and 4.1 months in the standard care arm (HR 0.85, 95% CI 0.67-1.11, P=0.23). Overall response rates were also similar between the groups (20% in the TTFields arm and 17% in the standard care arm).

All-grade adverse event (AE) rates were comparable between the two groups (97% and 91%, respectively) as were grade ≥3 AEs (59% and 56%). One notable difference between the groups was the incidence of dermatitis, which occurred in 43% of patients in the TTFields arm and 2% in the standard-of-care arm.

The involved 276 patients from 124 sites in 17 countries. Patients were randomized 1:1 to receive TTFields therapy and standard of care or standard of care alone (evenly split between ICIs and docetaxel). Patients were followed up every 6 weeks and continued on therapy until progression or intolerable toxicity.

Median age was 64 years, and 65% were men. The vast majority of patients (96%) had an Eastern Cooperative Oncology Group (ECOG) performance status score of 0-1, and 84% were current or former smokers.

The majority (56%) of patients had nonsquamous histology, 89% had one prior line of systemic therapy, and 31% had been previously treated with an ICI.

With TTFields technology, the electric fields are generated via a portable, wearable medical device and delivered to lung tumors by two pairs of arrays applied to the chest. Patients were advised to use the device continuously for around 18 hours per day.

While TTFields is noninvasive, "it is bulky," Heist commented. "I'd be interested to see what the quality-of-life outcomes are."

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