Hot flashes and night sweats are common in cancer survivors, particularly women, but they can also occur in men. Pathophysiological mechanisms are complex. Treatment options are broad-based and include hormonal agents, nonhormonal pharmacotherapies, and diverse integrative medicine modalities.

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Hot flashes, also called hot flushes, occur in approximately two-thirds of postmenopausal women with a history of breast cancer and are associated with night sweats in 44% of these women. The severity of hot flashes in patients with breast cancer has been associated with sleep difficulty, higher pain severity, and poor psychological functioning. In premenopausal breast cancer survivors, vasomotor symptoms—including hot flashes and night sweats—have been associated with depression, an effect that may be mediated by sleep disturbance. For most patients with breast cancer or prostate cancer, hot flash intensity is moderate to severe. Sweating can be part of the hot flash complex that characterizes the vasomotor instability of menopause. Physiologically, sweating mediates core body temperature by producing transdermal evaporative heat loss. Hot flashes accompanied by sweating that occur during the sleeping hours are often called night sweats.

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Approximately 20% of women without breast cancer seek medical treatment for postmenopausal symptoms, including symptoms related to vasomotor instability. Vasomotor symptoms resolve spontaneously in most patients in this population, with only 20% of affected women reporting significant hot flashes 4 years after the last menses. There are no comparable data for women with metastatic breast cancer. Three-quarters of men with locally advanced or metastatic prostate cancer treated with medical or surgical orchiectomy experience hot flashes.

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Etiology

Causes of menopausal hot flashes include natural menopause, surgical menopause, or chemical menopause. In patients with cancer, chemical menopause may be caused by the following:

• Cytotoxic chemotherapy.

• Radiation therapy.

• Androgen treatment.

Causes of so-called male menopause include the following:

• Orchiectomy.

• Gonadotropin-releasing hormone use.

• Estrogen use.

Drug-associated causes of hot flashes and night sweats in men and women include use of the following:

• Tamoxifen.

• Aromatase inhibitors.

• Opioids.

• Tricyclic antidepressants.

• Steroids.

Women who are extensive metabolizers of tamoxifen related to CYP2D6 may have more severe hot flashes than women who are poor metabolizers; however, conflicting data surround this topic.

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Primary Interventions

Lifestyle and Supportive Measures

Lifestyle modification should be recommended for all patients, although evidence for symptom reduction is modest. These strategies primarily reduce symptom burden and improve patient comfort.

Patients should be advised to:

• Maintain a healthy body weight

• Undertake regular physical activity

• Stop smoking

• Limit alcohol intake

• Reduce caffeine consumption if identified as a trigger

• Avoid spicy foods where relevant

• Keep bedrooms cool

• Use fans or air conditioning

• Wear loose-fitting, layered cotton clothing

• Use breathable cotton bedding

• Maintain good sleep hygiene

• Identify and avoid individual triggers

Although these interventions rarely eliminate vasomotor symptoms, they are low risk and may improve overall wellbeing.

 

Cognitive and Behavioural Interventions

Psychological interventions are recommended as part of a multimodal management strategy, particularly in patients experiencing significant symptom-related distress.

Cognitive behavioural therapy (CBT) is the best studied behavioural intervention. Rather than reducing the physiological occurrence of hot flushes, CBT primarily decreases the perceived burden and interference associated with symptoms by improving coping strategies.

Typical CBT programmes include:

• Psychoeducation regarding menopause and cancer treatment

• Cognitive restructuring to address catastrophic thinking

• Stress management techniques

• Relaxation training

• Sleep optimisation strategies

• Behavioural modification

Large randomized trials have consistently demonstrated significant improvements in:

• Hot flush bother

• Symptom distress

• Sleep quality

• Quality of life

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However, CBT generally does not significantly reduce hot flush frequency, and should therefore be viewed as an adjunct rather than a replacement for pharmacological therapy.

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Relaxation techniques and paced breathing were initially reported to reduce symptom intensity by 40–50%; however, subsequent randomized controlled trials failed to demonstrate clinically meaningful reductions in hot flash frequency. Consequently, paced breathing is no longer routinely recommended as a stand-alone intervention.

Medical hypnosis has demonstrated promising results in randomized studies, with reductions in hot flash frequency of approximately 64% after six weeks and 75% after twelve weeks, substantially outperforming attention-control interventions. Although evidence in cancer survivors remains limited, hypnosis may be considered where appropriately trained practitioners are available.

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Pharmacological Management

Hormone replacement therapy (HRT) remains the most effective treatment for menopausal vasomotor symptoms in the general population. However, systemic hormone therapy is generally contraindicated in patients with hormone receptor-positive breast cancer because of concerns regarding recurrence risk. Consequently, non-hormonal therapies represent first-line pharmacological management for most oncology patients.

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Selective Serotonin Reuptake Inhibitors (SSRIs)

SSRIs reduce vasomotor symptoms by modulating hypothalamic thermoregulation through serotonergic pathways.

Agents with evidence of benefit include:

• Escitalopram

• Citalopram

• Paroxetine

• Fluoxetine

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Symptom reductions of approximately 40–65% have been reported.

However, important drug interactions must be considered.

Paroxetine and fluoxetine should be avoided in patients receiving tamoxifen, as both are potent CYP2D6 inhibitors that reduce formation of tamoxifen's active metabolite (endoxifen), potentially reducing treatment efficacy.

Preferred SSRIs in women taking tamoxifen include:

• Escitalopram

• Citalopram

Common adverse effects include:

• Nausea

• Headache

• Dry mouth

• Sexual dysfunction

• Insomnia

• Withdrawal symptoms if discontinued abruptly

 

Serotonin-Noradrenaline Reuptake Inhibitors (SNRIs)

Venlafaxine is among the best-studied non-hormonal treatments for hot flushes in oncology.

Randomized trials demonstrate reductions in hot flush frequency of approximately 50–60%, with benefit often occurring within one to two weeks.

Typical dosing:

• 37.5 mg daily for one week

• Increase to 75 mg daily if required

Desvenlafaxine has demonstrated similar efficacy.

Potential adverse effects include:

• Nausea

• Dry mouth

• Constipation

• Hypertension (dose related)

• Insomnia

 

Venlafaxine is particularly useful in patients with coexisting anxiety or depression and does not significantly inhibit CYP2D6.

Gabapentinoids

 

Gabapentin is an effective non-hormonal therapy that is particularly useful in patients whose symptoms predominantly occur at night.

Typical dosing:

• Start 100–300 mg nocte

• Gradually titrate to 900 mg/day in divided doses if required

Randomized trials demonstrate reductions in symptom frequency of approximately 45–60%.

Benefits include:

• Improved sleep

• Reduced nocturnal hot flushes

Common adverse effects include:

• Somnolence

• Dizziness

• Peripheral oedema

• Fatigue

Pregabalin has also demonstrated efficacy but is generally associated with a higher incidence of adverse effects.

 

Oxybutynin

Oxybutynin, an anticholinergic medication traditionally used for overactive bladder, has emerged as an effective treatment for refractory hot flushes.

Randomized trials demonstrate significant reductions in:

• Hot flash frequency

• Symptom severity

• Quality-of-life impairment

Common adverse effects include:

• Dry mouth

• Constipation

• Blurred vision

• Urinary retention

• Cognitive impairment, particularly in older adults

Oxybutynin should therefore be used cautiously in elderly patients.

 

Clonidine

Clonidine has historically been used for vasomotor symptoms but is now recommended less frequently due to relatively modest efficacy and frequent adverse effects.

Common side effects include:

• Dry mouth

• Dizziness

• Constipation

• Sedation

• Postural hypotension

Current guidelines generally favour SSRIs, SNRIs or gabapentin over clonidine.

 

Hormonal Therapy

Hormone replacement therapy is highly effective for vasomotor symptoms but requires careful consideration in oncology populations.

Generally contraindicated

• Hormone receptor-positive breast cancer

• Patients receiving tamoxifen or aromatase inhibitors

May occasionally be considered after specialist consultation in carefully selected patients with:

• Severe refractory symptoms

• Non-hormone-sensitive malignancies

• Individualised risk-benefit assessment

Routine use is not recommended.

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Complementary and Integrative Therapies

 

Many patients seek complementary therapies; however, evidence supporting their use remains limited.

Soy isoflavones

Although widely used, multiple randomized controlled trials demonstrate no clinically meaningful benefit over placebo. Given their phytoestrogenic properties, soy supplements are not routinely recommended in patients with hormone-sensitive cancers.

Black cohosh

Several randomized controlled trials and meta-analyses demonstrate no significant benefit compared with placebo. Current evidence does not support routine use.

Vitamin E

Vitamin E (400 IU twice daily) provides only modest benefit, producing approximately 35–40% reduction in hot flashes, only slightly greater than placebo. Routine use is generally not recommended.

Flaxseed

Early pilot studies suggested benefit; however, larger randomized phase III trials failed to demonstrate efficacy.

Magnesium

Despite encouraging preliminary data, randomized placebo-controlled trials showed no benefit.

Acupuncture

Evidence remains inconsistent.

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Meta-analyses generally conclude acupuncture has limited or no significant effect on hot flash frequency in breast cancer survivors, although some individual randomized trials have demonstrated improvements in symptom severity and quality of life. Electroacupuncture has shown efficacy comparable to gabapentin in some studies and may improve sleep quality. Acupuncture may therefore be considered for selected patients who prefer non-pharmacological treatment, provided expectations are realistic.

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Management Algorithm

A practical approach for oncology patients includes:

1. Assess symptom severity, impact on quality of life and exclude alternative causes.

2. Initiate lifestyle advice and education for all patients.

3. Offer CBT where symptoms significantly affect quality of life or coping.

4. Commence non-hormonal pharmacotherapy if symptoms remain moderate to severe:

   • Venlafaxine or escitalopram/citalopram are common first-line options.

   • Gabapentin is particularly useful for nocturnal symptoms.

   • Oxybutynin may be considered for refractory cases.

5. Avoid paroxetine and fluoxetine in patients receiving tamoxifen.

6. Reserve hormone replacement therapy for carefully selected patients following specialist multidisciplinary discussion.

 

Key Clinical Points

Hot flushes and night sweats are among the most common adverse effects of endocrine therapy and androgen deprivation therapy and are a major contributor to impaired quality of life and treatment non-adherence. Management should be individualised and combine education, lifestyle modification, behavioural interventions and evidence-based non-hormonal pharmacological therapies. SSRIs, SNRIs, gabapentin and oxybutynin currently have the strongest evidence supporting efficacy in oncology populations, whereas complementary therapies such as soy, black cohosh, flaxseed and magnesium have not consistently demonstrated benefit and should not be routinely recommended. Hormone replacement therapy remains contraindicated in most patients with hormone-sensitive cancers and should only be considered after specialist multidisciplinary assessment.