OncologyTier 1Topic

Side effects of systemic cancer therapy - alopecia

Patterns

Hair loss from systemic anti-cancer therapy - ranges from diffuse thinning to complete scalp/body hair loss
Anagen effluvium - the chemotherapy pattern - abrupt loss of actively-growing (anagen) follicles, hair loss within 2-4 weeks of starting treatment
Telogen effluvium - a milder pattern (endocrine therapy, some targeted agents) - follicles prematurely shift into resting phase, more gradual/diffuse thinning
Persistent (endocrine therapy-induced or post-chemotherapy) alopecia - failure of regrowth after treatment completion - increasingly recognised, particularly with taxanes and aromatase inhibitors

Near-universal (>80%) with anthracyclines, taxanes, and high-dose alkylating regimens
Lower incidence with many targeted therapies/immunotherapy, though EGFR inhibitors and some TKIs cause distinct hair changes (thinning, curling, brittle texture)
Persistent chemotherapy-induced alopecia - affects a minority (estimates vary, up to ~10-30% in some taxane series) but has disproportionate psychological impact given the expectation of regrowth

Cytotoxic chemotherapy targets rapidly dividing cells - anagen-phase hair matrix cells are highly mitotically active and vulnerable, explaining the rapid, near-total pattern with anthracycline/taxane regimens
Endocrine therapy (aromatase inhibitors, tamoxifen) - oestrogen contributes to anagen phase maintenance; withdrawal shifts follicles toward telogen -> diffuse thinning, generally milder and slower than cytotoxic-induced loss
Targeted therapy/TKI-associated changes - mechanism less clear, often affects hair texture/curl pattern as much as density
Persistent alopecia - thought to reflect follicular stem cell damage/depletion rather than simple delayed regrowth

Clinical - diagnosis by history and timing

Temporal relationship to treatment, pattern (diffuse vs patchy), and drug class are usually sufficient
Persistent alopecia - diagnosed when hair fails to regrow to baseline density by ~6-12 months after treatment completion

Patchy/scarring alopecia, or a pattern atypical for the drug given, warrants dermatology review and consideration of trichoscopy/scalp biopsy to exclude an alternative cause (alopecia areata, scarring alopecia)
Exclude other contributors to hair loss - iron deficiency, thyroid dysfunction - particularly if the pattern seems disproportionate to the treatment received

A. Prevention - during treatment

Scalp cooling (cold cap) - reduces scalp blood flow during infusion, lessening drug delivery to follicles - can meaningfully reduce chemotherapy-induced alopecia severity with certain regimens (more effective with taxanes than anthracyclines); requires consideration of theoretical scalp metastasis risk (low, but discussed in counselling), not universally available/subsidised

B. During and after treatment

Counselling and psychological support - alopecia is consistently reported by patients as one of the most distressing side effects, independent of prognosis
Wigs, head coverings - practical/cosmetic support, often subsidised via cancer support programs
Reassurance that hair typically regrows after chemotherapy completion (though texture/colour may change - "chemo curl")

C. Persistent alopecia

Topical minoxidil - first-line trial for persistent post-chemotherapy or endocrine therapy-associated alopecia, modest evidence of benefit
Dermatology referral for refractory cases - consider other adjuncts (low-level laser therapy, platelet-rich plasma - evidence limited)
Set realistic expectations early - persistent alopecia should be discussed proactively with taxane/aromatase inhibitor regimens rather than only after it occurs

Regimen-specific: anthracyclines, taxanes, cyclophosphamide (high rates); endocrine therapy, some TKIs (milder, more gradual)
Nail changes, skin toxicity - often co-occur with the same agents (e.g. taxane-associated nail dystrophy)
Body image disturbance, anxiety, depression - alopecia is an independent driver of treatment-related psychological distress

Chemotherapy-induced alopecia - typically begins 2-4 weeks after starting treatment, and regrowth begins within 1-3 months of completion in most patients
Regrown hair may differ in texture/colour/curl from baseline ("chemo curl") - usually temporary, normalising over 6-12 months
Persistent alopecia - by definition does not fully reverse; management shifts from "waiting for regrowth" to active treatment (minoxidil) and cosmetic/psychological support
Endocrine therapy-associated thinning - often continues for the duration of therapy (which may run 5-10 years), a distinct long-term counselling point from the acute chemotherapy pattern

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