1851P - Tumor treating fields plus chemotherapy for first-line malignant pleural mesothelioma (MPM): Radiological responses in the STELLAR trial

Abstract

BackgroundTumor Treating Fields (TTFields) are an anti-mitotic, regional treatment modality, utilizing low intensity alternating electric fields delivered non-invasively to the tumor. TTFields have significantly extended survival of patients with glioblastoma. In vitro, human MPM cells are highly susceptible to TTFields. In the phase 2 STELLAR study [NCT02397928], patients with unresectable MPM treated with first line chemotherapy in combination with TTFields had a significantly higher median overall survival compared with historical controls (18.2 Vs. 12.1 months). We report on radiological data from STELLAR patients whose tumors responded while receiving the combined therapy. MethodsThe STELLAR trial accrued 80 patients with unresectable, previously untreated MPM. Patients received continuous 150kHz TTFields (>18h/day) combined with pemetrexed and cisplatin or carboplatin (standard dosing). Inclusion criteria: ECOG PS of 0-1, pathologically proven MPM and > measurable lesion per modified RECIST. Patients were followed q3w (CT scan q6w) until disease progression. Radiological assessments were done 6-weekly at study sites. ResultsPartial responses (PRs) were seen in 40.3% (29/72) of evaluable patients and clinical benefit (PR+SD) was seen in 97.2% (70/72) patients. The median time between treatment start and PR was 1.9 months (range: 1.4-4.4 months). All patients presenting with PR during the STELLAR study had continuous reduction in the total sum of lesion diameters, suggesting no initial/pseudo-progression. 83% of the patients who responded to the combined therapy finally had disease progression with a median response duration of 5.7 months (range: 1.4-13 months). One patient did not progress for more than 27 months. 28 responders (97%) reported at least 1 adverse event, and 7 patients (24%) had TTFields-related skin toxicities. ConclusionsThe STELLAR study significantly extended survival in previously untreated MPM patients. Response rates were similar to those reported for the current MPM standard of care treatment, but were of longer duration with the addition of TTFields. The only TTFields-related adverse event was skin irritation beneath the arrays. Clinical trial identificationNCT02397928. Legal entity responsible for the studyNovocure. FundingNovocure. DisclosureF. Grosso: Travel / Accommodation / Expenses: Novocure. G.L. Ceresoli: Travel / Accommodation / Expenses: Novocure.