Table 1.

Dermatologic scalp adverse event (AE) types, symptomatology, potential causes, and treatment recommendations (24, 37–40).

Case 1: Tumor Treating Fields (TTFields) AE - hyperhidrosis
	Symptomatology	Potential Cause(s)
	• Excessive sweating from scalp	• Genetic predisposition • Hot/humid climate • Intense activity • Medications
Suggested Intervention(s) • Treat with aluminum chloride antiperspirant or topical glycopyrrolate at every array exchange • Advise patients to avoid using ointments and medications that may cause sweating • Consider referral to a dermatologist for botulinum toxin injections
Case 2: TTFields AE – pruritus
	Symptomatology	Potential Cause(s)
	• Dry skin (xerosis) • Itchy skin (pruritus) • Flaky skin (dandruff)	• Genetic predisposition • Cold/dry climate • Loss of water/oil • Medications • May be related to contact dermatitis
Suggested Intervention(s) • Advise patients to use fragrance-free or anti-dandruff shampoo • Although part of the standard array change protocol, limit skin contact with alcohol-based products • Topical corticosteroids may be prescribed if inflammation is present (e.g., betamethasone, clobetasol, fluocinonide) • Identify cause and, if possible, reduce/eliminate
Case 3: TTFields AE – contact dermatitis
	Symptomatology	Potential Cause(s)
	Contact
	• Skin rash characterized by red, itching papules • May resemble a burn • Rash may present with red bumps that form moist, weeping blisters • Localized yet may be more diffuse than irritant type dermatitis	• Allergy to specific exogenous allergens, such as adhesive tape and/or hydrogel, that come into contact with the skin causing an inflammatory reaction
	Irritant
	• Skin redness • Mild edema • Scaling • Rash that may be itchy or painful • Dermatitis restricted locally to the area of the irritant	• Non-specific inflammation caused by direct cellular damage upon contact with an inherently harmful substance to cells (e.g., chemical irritation from hydrogel, moisture, and/or alcohol)
Suggested Intervention(s) • Immediate removal of the irritant/allergen • Transducer array removal from irritation/allergen site • Topical corticosteroid (e.g., betamethasone, clobetasol, fluocinonide) application • Apply a barrier film • Consider trimming adhesive/surgilast if reaction exists to tape/adhesive • If blistering develops, cold, moist compress application (20 min; 3 times/day) is recommended • Consider systemic corticosteroids/treatment breaks if condition persists
Case 4: TTFields AE – erosion; and TTFields + bevacizumab AE – ulceration with hardware exposure
	Symptomatology Erosion	Potential Cause(s)
	• Breakdown of the outer epidermal layer of skin • Skin discontinuity marked by incomplete loss of the epidermis • May present as a delineated moist or depressed lesion • Mild bleeding with pain or burning may be present • Typically, erosions do not result in scarring	• Mechanical trauma from shaving and/or array application/ removal • May develop from inflammation or maceration due to sweat, rupture of vesicles, bullae from infection, or epidermal necrosis
	Ulcer
	• Open scalp skin defects with potential for bleeding or oozing • Complete loss of epidermis and portions of the dermis, fat, or muscle, with increased risk of scarring • Pustules may develop when infected	• Ischemic injury and/or decreased perfusion produced by array pressure (especially in areas overlying scars, hardware, and prior radiation exposure
Suggested Intervention(s) • Transducer array removal from site of erosion/ulcer – consider re-placement to avoid hardware exposure • Wound dressing with gauzes, hydrogels, or hydrocolloids • Assess wound and treat with topical antibiotic (e.g., clindamycin, gentamicin) • Consider wound culture • Keep clear of excess discharge and dead skin (severe cases may require surgical debridement) • Return to clinic in 2 weeks; if condition persists, consider oral antibiotic/treatment break
Case 5: TTFields AE – dermatitis + infections
	Symptomatology	Potential Cause(s)
	• Inflammation of skin or hair follicle (red pimple with hair in the center) • May have pus, itching, or burning	• Secondary bacterial infection • Ultimately, infection with or without pustules may occur when the skin is affected by pathogenic bacteria
Suggested Intervention(s) • Assess wound and treat with topical antibiotic (e.g., clindamycin or gentamicin) • Warm compresses with saltwater or Burow's solution (5% aluminum subacetate) • Take wound culture and potentially refer to dermatologist • Return to clinic in 2 weeks; if condition persists, consider oral antibiotic/treatment break