ACTR-10. PATTERNS OF TTFIELDS-RELATED SEVERE SKIN TOXICITY IN GBM PATIENTS

Tumor Treating Fields (TTFields) are a medical device-based anti-mitotic therapy, which has demonstrated significant survival superiority when combined with maintenance temozolomide in a phase III trial in newly-diagnosed glioblastoma. Local dermatitis underneath the arrays is the only frequent TTFields-related adverse event (AE), and is reported in around 50% of all patients treated with TTFields across different cancers. Only 1–3% of these patients have a high grade severity of this AE. TTFields-related dermatitis is assumed to be primarily caused by the continuous exposure of the skin to array components (Lacouture ME, et al., 2014). We analyzed patterns related to the appearance of severe skin toxicity in the seven newly-diagnosed GBM patients reported to have this adverse event on the EF-14 trial. A total of 466 patients received TTFields on the EF-14 study, out of which 242 (52%) were reported to have dermatitis. Biopsy only patients had lower incidence of the AE as did patients who used the device for less hours a day, but other patient characteristics were balanced between TTFields-treated patients with or without dermatitis. In patients who had severe skin toxicity, the median time from the initiation of TTFields to the first diagnosis of any TTFields-related skin toxicity was 18.5 days (range: 11–89 days). The following TTFields-related skin toxicities were reported: Rash, irritation, erythema, pruritus, contact dermatitis, ulceration, infection and skin breakdown. All patients had low-grade skin toxicity (CTCAE grade 1–2) prior to presenting with grade 3 toxicity. No grade 4 (life-threatening) event was reported. The median duration of severe skin toxicity was 17 days (range: 2–61 days), and all of them resolved without sequelae. These results indicate that severe skin toxicity is always preceded by lower grade skin toxicity, suggesting that proper identification and treatment of low grade dermatitis may prevent severe skin toxicity related to TTFields.