How Does Chemotherapy Work?
Chemotherapy (often called "chemo") uses powerful medications (cytotoxic drugs) to kill cancer cells or stop them from growing. Because these drugs travel through your bloodstream (systemic therapy), they can affect your healthy cells too — especially fast-growing ones like hair, blood, and digestive cells. This is what causes most side effects. Your treatment plan may include one or more types of chemotherapy drugs. Common drug classes used for breast cancer include:- Anthracyclines — such as doxorubicin (Adriamycin) or epirubicin (Ellence)
- Taxanes — such as paclitaxel (Taxol) or docetaxel (Taxotere)
- Alkylating agents — such as cyclophosphamide (Cytoxan)
- Platinum agents — such as carboplatin (Paraplatin)
Side Effects During Treatment (Acute Side Effects)
These typically begin within days of each treatment cycle and often improve between cycles. They are grouped below by how commonly they occur.Common (Most People Experience These)
Fatigue (Cancer-Related Fatigue, or CRF) This is the most common side effect of chemotherapy, affecting up to 80–96% of patients. It is different from normal tiredness and may not fully improve with rest alone. Nausea and Vomiting (Chemotherapy-Induced Nausea and Vomiting, or CINV) One of the most well-known side effects. Your care team will prescribe anti-nausea medications (antiemetics) before and after each of your treatments to prevent this. Your nausea can be acute (within 24 hours of treatment) or delayed (more than 24 hours after treatment). Up to 60% of patients receiving antineoplastic treatment will experience some degree of nausea or vomiting, though modern antiemetic regimens have significantly reduced the severity. Hair Loss (Alopecia) Most chemotherapy regimens for breast cancer cause partial or complete hair loss, including scalp hair, eyebrows, eyelashes, and body hair. Severe alopecia (more than 50% hair loss) is reported in over 70% of patients receiving anthracycline- and taxane-based regimens, with rates approaching 90–100% in combination regimens. Your hair almost always grows back after treatment ends, though it may return with a different texture or colour. However, emerging data suggest that persistent partial hair loss may be more common than previously recognised, occurring in up to 40–67% of patients treated with certain regimens. Your care team may offer you scalp cooling (also called cold caps or scalp hypothermia) to reduce hair loss. In clinical trials, scalp cooling reduced the risk of severe hair loss (more than 50%) by approximately 43–50%, with success rates of 40–75% depending on the chemotherapy regimen. Results may be less effective with anthracycline-containing regimens. Scalp cooling has not been shown to increase the risk of cancer spreading to the scalp. A recent randomised trial also showed that scalp cooling reduced persistent hair loss at 6 months after chemotherapy (13.5% vs 52% in the control group), primarily by improving hair thickness during regrowth. Low Blood Counts (Myelosuppression or Bone Marrow Suppression) Chemotherapy can temporarily lower your blood cell counts:- Low white blood cells (neutropenia) — increases your risk of infection. A dangerously low count with fever is called febrile neutropenia, which is a medical emergency.
- Low red blood cells (anemia) — can cause fatigue, shortness of breath (dyspnea), and dizziness. Chemotherapy-induced anemia is extremely common, affecting virtually all patients to some degree, with approximately 15% developing severe anemia.
- Low platelets (thrombocytopenia) — increases your risk of bleeding or bruising.
Less Common (Some People Experience These)
Mouth Sores (Oral Mucositis or Stomatitis) You may develop painful sores or inflammation in your mouth and throat that can make eating and drinking difficult. The incidence varies by regimen — mucositis/stomatitis occurs in approximately 26–60% of patients depending on the drugs used. Skin and Nail Changes Chemotherapy can cause a range of skin and nail changes. Skin reactions may include dryness (xerosis), rashes, darkening (hyperpigmentation), and hand-foot syndrome (palmar-plantar erythrodysesthesia) — redness, swelling, and peeling on the palms and soles. Nail changes occur in approximately 34–45% of patients and may include discolouration, brittleness, ridging (Beau's lines), loosening of the nail from the nail bed (onycholysis), or painful inflammation around the nail (paronychia). Taxanes, particularly docetaxel, are most commonly associated with nail toxicity. These changes are usually temporary and improve after treatment ends. Eye Problems (Ocular Toxicity) Taxane-based chemotherapy, particularly docetaxel, can cause excessive tearing (epiphora) in up to 39–86% of patients, depending on the schedule. This is caused by inflammation and narrowing of the tear drainage channels (canalicular stenosis). Tearing usually resolves within a few months of completing treatment. Less commonly, taxanes may be associated with blurred vision or other eye changes. Report any new eye symptoms to your care team. Allergic or Infusion Reactions (Hypersensitivity Reactions) Some drugs, especially taxanes, can cause reactions during your infusion, including flushing, rash, shortness of breath, or changes in blood pressure. You will receive premedications (such as corticosteroids and antihistamines) to help prevent this. Blood Clots (Venous Thromboembolism, or VTE)Chemotherapy increases the risk of blood clots, including deep vein thrombosis (DVT) and pulmonary embolism (PE). The risk of symptomatic VTE in ambulatory patients receiving chemotherapy is approximately 3–10%, depending on cancer type, stage, and treatment. Your care team may assess your risk using a scoring system (such as the Khorana score) and may recommend preventive blood-thinning medication (thromboprophylaxis) if your risk is elevated.
Signs to watch for include new leg swelling, pain, or warmth (possible DVT), or sudden shortness of breath or chest pain (possible PE). These require immediate medical attention.Side Effects That May Develop Later (Long-Term and Late Effects)
Some side effects persist after your treatment ends or appear months to years later.More Common Late Effects
Peripheral Neuropathy (Nerve Damage) You may experience numbness, tingling, burning, or pain in your hands and feet — most commonly caused by taxanes. This is called chemotherapy-induced peripheral neuropathy (CIPN). It affects 30–50% of cancer survivors and may improve after treatment ends, but can sometimes be permanent in 20–30% of cases. Your care team may recommend cryotherapy (cooling gloves and socks worn during your infusions) to help reduce your risk. A systematic review and meta-analysis of 17 trials found that cryotherapy significantly reduced the incidence of CIPN, with a risk ratio of 0.54 at the end of chemotherapy. The ASCO guideline notes that while definitive proof of benefit has not been fully established, available data support that cryotherapy, compression therapy, and/or cryo-compression therapy may help prevent CIPN symptoms and appear to be reasonably safe. Exercise during taxane-based chemotherapy has also been shown to reduce CIPN symptoms. Cognitive Changes ("Chemo Brain" or Chemotherapy-Induced Cognitive Impairment) You may notice difficulty with memory, concentration, multitasking, or finding words. Up to 75% of patients report some cognitive difficulties during treatment, and approximately one-third of survivors report ongoing impairment after treatment ends. Both chemotherapy and endocrine therapy can contribute. Importantly, chemo brain is usually not progressive — it is different from conditions like dementia and often improves over time. Fertility and Menstrual Changes (Gonadotoxicity) Chemotherapy — especially alkylating agents like cyclophosphamide — can damage your ovaries, leading to irregular periods, early menopause (premature ovarian failure), or infertility. Your risk is higher if you are over 35. Although amenorrhea frequently occurs during or after chemotherapy, the majority of patients under 35 resume menses within 2 years of finishing adjuvant chemotherapy. However, menses and fertility are not necessarily linked — the absence of regular periods does not necessarily imply infertility, and the presence of menses does not guarantee fertility. Menopausal symptoms may include hot flashes, night sweats, vaginal dryness (atrophic vaginitis), mood changes, and sleep problems. Sexual Health Changes Up to 75% of women treated for breast cancer report some degree of sexual dysfunction. Common concerns include decreased sexual desire (23–64% of patients), arousal or lubrication difficulties (20–48%), orgasmic concerns (16–36%), and painful intercourse or dyspareunia (35–38%). Patients who receive chemotherapy tend to have more sexual concerns than those treated with surgery and/or radiation alone. These changes can result from a combination of physical effects (hormonal changes, vaginal dryness, fatigue, body image changes from hair loss and other visible side effects) and psychological factors (anxiety, depression, changes in self-image). Your care team can help — treatments include nonhormonal lubricants and moisturizers, pelvic floor therapy, and counselling. Do not hesitate to raise these concerns with your doctor or nurse. Weight Changes Weight gain is common during and after chemotherapy for breast cancer. Maintaining a healthy weight through balanced nutrition and regular physical activity is important for your long-term health and may reduce your risk of cancer recurrence. Bone Thinning (Osteoporosis and Osteopenia) Chemotherapy-induced early menopause and certain hormonal therapies (aromatase inhibitors) can weaken your bones, increasing your risk of fractures. Your care team may order a bone density scan (DXA scan) and recommend calcium, vitamin D supplements, and weight-bearing exercise.Less Common Late Effects
Heart Problems (Cardiotoxicity) Anthracyclines (like doxorubicin) can damage your heart muscle, potentially leading to cardiomyopathy (weakened heart muscle) or congestive heart failure (CHF). Clinically significant congestive heart failure develops in approximately 0.5–3% of women treated with standard anthracycline-based regimens, with risk increasing at higher cumulative doses. Importantly, the risk of congestive heart failure does not appear to plateau over time — long-term survivors may have continued risk even years after treatment. HER2-targeted therapies (like trastuzumab/Herceptin), often given alongside chemotherapy, can also affect your heart function. Your care team will monitor your heart's pumping ability (left ventricular ejection fraction, or LVEF) with echocardiograms or MUGA scans before and during your treatment. Blood Cancers (Very Rare Late Effect) There is a very small risk (approximately 0.2–1%) of developing a blood cancer such as myelodysplastic syndrome (MDS) or acute leukemia years after treatment with certain chemotherapy drugs (alkylating agents and anthracyclines). Two distinct types have been described: leukemias associated with alkylating agents (such as cyclophosphamide) may arise 5–7 years after treatment, while those associated with topoisomerase inhibitors (such as anthracyclines) may appear 6 months to 5 years after therapy. This is rare, and the absolute risk is far lower than the survival benefit provided by adjuvant chemotherapy. Your care team will continue to monitor your blood counts during follow-up.The Role of Exercise During Chemotherapy
Staying physically active during chemotherapy is one of the most effective strategies for managing side effects and improving your quality of life. ASCO guidelines recommend aerobic and resistance exercise during active treatment with curative intent to mitigate side effects of cancer treatment. Clinical trials and meta-analyses have shown that exercise during chemotherapy can:- Significantly reduce fatigue — the most common and distressing side effect
- Preserve cardiorespiratory fitness, physical functioning, and strength
- Improve quality of life, including physical, emotional, and social functioning
- Reduce symptoms of anxiety and depression
- Help reduce chemotherapy-induced peripheral neuropathy symptoms
- Improve body image
Complementary Therapies: Acupuncture
Acupuncture is a technique in which thin needles are placed at specific points on your body. It has been studied in high-quality clinical trials for several chemotherapy side effects and is now included in guidelines from the National Comprehensive Cancer Network (NCCN) and the American Society of Clinical Oncology (ASCO) as a complementary therapy option. Acupuncture is used alongside — not instead of — your standard medical treatment. Evidence supports acupuncture for the following side effects relevant to you as a chemotherapy patient:- Nausea and vomiting — NCCN guidelines include acupuncture as a complementary approach for chemotherapy-induced nausea and vomiting. A clinical trial of 239 breast cancer patients receiving highly emetogenic (strong nausea-causing) chemotherapy found that adding electroacupuncture (acupuncture with mild electrical stimulation) to standard anti-nausea medications significantly improved nausea control — the complete protection rate increased from about 35% to 53%.
- Peripheral neuropathy (CIPN) — Both ASCO and NCCN guidelines include acupuncture as a non-medication option for chemotherapy-induced nerve pain and numbness. Multiple clinical trials in breast cancer patients have shown that acupuncture courses (typically 8 weeks) can significantly improve neuropathic pain and sensory symptoms. A recent large clinical trial (ABC-CIPN) in early breast cancer patients with taxane-induced neuropathy showed clinically meaningful improvements in quality of life and pain.
- Cancer-related fatigue — NCCN guidelines recommend acupuncture as a non-medication option for fatigue both during active treatment and after treatment ends. A clinical trial of over 300 breast cancer patients with persistent fatigue found that acupuncture significantly reduced fatigue compared to usual care alone.
- Joint pain from hormonal therapy (aromatase inhibitors) — If you are also taking an aromatase inhibitor (such as letrozole, anastrozole, or exemestane), acupuncture has the strongest evidence of any complementary therapy for this type of joint pain. NCCN gives it their highest level of recommendation (category 1). A major clinical trial (SWOG S1200) of 226 women published in JAMA showed that acupuncture significantly reduced joint pain compared to both sham (placebo) acupuncture and no treatment, with benefits lasting up to one year.
- Hot flashes — NCCN guidelines include acupuncture as a non-medication option for hot flashes related to your cancer treatment or treatment-induced menopause. Clinical trials in breast cancer patients have shown meaningful improvements in hot flash frequency and severity, as well as overall quality of life.
- Acupuncture has a very good safety record in cancer patients. The most common side effects are mild bruising or soreness at the needle sites. No serious side effects have been reported in cancer clinical trials.
- Look for a licensed acupuncturist, ideally one with experience treating cancer patients. Your care team may be able to recommend someone, and some cancer centres have integrative medicine programs that include acupuncture.
- Insurance coverage for acupuncture varies. Check with your insurance plan about coverage, and ask your care team if a referral or prescription is needed.
- Always tell your acupuncturist about your cancer treatment, including any blood-thinning medications or low blood counts (especially around your nadir), so they can take appropriate precautions.
Emotional and Psychological Effects
Feelings of anxiety, depression, sadness, fear of recurrence, and distress are very common during and after chemotherapy. These are normal responses to a difficult experience.When to Call Your Care Team
Contact your doctor or nurse right away if you experience:- Fever of 100.4°F (38°C) or higher — this could be a sign of neutropenic fever, which is a medical emergency
- Severe or bloody diarrhea, or inability to keep fluids down
- Mouth sores that prevent you from eating or drinking
- New or worsening numbness or tingling in your hands or feet
- Shortness of breath, chest pain, or rapid heartbeat (tachycardia)
- Unusual bleeding or bruising (petechiae — small red or purple spots on your skin)
- Signs of infection: redness, swelling, warmth, or pus at any site
- Severe fatigue that does not improve with rest
- New leg swelling, pain, or warmth (possible blood clot)
- Sudden shortness of breath or chest pain (possible pulmonary embolism)
- New or worsening eye symptoms, including excessive tearing or blurred vision
Practical Tips for Managing Side Effects
Nausea and appetite- Take your antiemetics exactly as prescribed — prevention works better than treatment
- Eat small, frequent meals; choose bland, room-temperature foods
- Avoid strong smells
- A dietary consult may also be helpful
- Light to moderate physical activity (such as walking) is one of the most effective ways to manage fatigue
- A combination of aerobic exercise and resistance training is recommended by guidelines
- Pace your activities and prioritize rest
- Discuss exercise with your care team, especially around your nadir
- Consider getting a wig, scarves, or hats before your treatment begins
- Many insurance plans cover wigs (sometimes called cranial prostheses) with a prescription
- Ask your care team about scalp cooling if you are interested
- Wash your hands frequently
- Avoid crowds and sick contacts when your counts are low (your nadir is usually 7–14 days after treatment)
- Call your care team immediately if you develop a fever of 100.4°F (38°C) or higher
- Use a soft toothbrush and gentle, alcohol-free mouthwash
- Avoid spicy, acidic, or very hot foods
- Stay well hydrated
- For diarrhea, stay hydrated and ask your care team about loperamide (Imodium)
- For constipation, increase your fluids and fiber, and ask about stool softeners
- Report severe or persistent symptoms
- Use gentle, fragrance-free moisturisers for dry skin
- Protect your nails from trauma; keep them trimmed short
- Frozen gloves or socks during infusions may help reduce nail toxicity from taxanes
- Avoid prolonged sun exposure to nails and skin
- Report any painful nail changes or hand-foot symptoms to your care team
- Use preservative-free artificial tears if you experience dryness or excessive tearing
- Report persistent tearing or vision changes to your care team
- Report any numbness or tingling early — your oncologist may adjust your dose to prevent worsening
- Ask your care team about cryotherapy (cooling gloves and socks) during taxane infusions
- Stay physically active — exercise has been shown to help reduce neuropathy symptoms
- Be careful with hot surfaces and sharp objects if you have reduced sensation
- Talk to your care team about any changes in sexual function — effective treatments are available
- Nonhormonal, water- or silicone-based lubricants can help with vaginal dryness
- Pelvic floor therapy and counselling may be helpful
- Body image concerns related to hair loss and other visible changes are common and valid — support is available
- Talk to your care team about how you are feeling
- Ask about counselling, support groups, or medications if needed
- Staying physically active, practising mindfulness, and maintaining social connections can also help
- Stay as active as possible; avoid prolonged immobility
- Stay well hydrated
- Report any new leg swelling, pain, or sudden shortness of breath immediately
- Maintain heart-healthy habits: stay active, eat well, manage your blood pressure and cholesterol, and avoid smoking
- Keep up with recommended bone density screening if you are at risk for osteoporosis
- Attend all follow-up appointments — your care team will continue to monitor your blood counts, heart function, and overall health
Quick Reference: Key Medical Terms
- Adjuvant chemotherapy — Chemotherapy given after surgery to reduce the risk of your cancer returning
- Neoadjuvant chemotherapy — Chemotherapy given before surgery to shrink your tumour
- Antiemetics — Medications to prevent or treat nausea and vomiting
- Myelosuppression — Reduced production of blood cells by your bone marrow
- Neutropenia — Low white blood cell count, increasing your infection risk
- Febrile neutropenia — Fever with a dangerously low white blood cell count — a medical emergency
- Anemia — Low red blood cell count, causing fatigue and weakness
- Thrombocytopenia — Low platelet count, increasing your bleeding risk
- Venous thromboembolism (VTE) — Blood clots in the veins, including deep vein thrombosis (DVT) and pulmonary embolism (PE)
- Alopecia — Hair loss
- Mucositis — Inflammation and sores in your mouth or digestive tract
- Peripheral neuropathy (CIPN) — Numbness, tingling, or pain in your hands and feet from nerve damage
- Onycholysis — Loosening or separation of the nail from the nail bed
- Epiphora — Excessive tearing of the eyes
- Cardiotoxicity — Damage to your heart from certain medications
- LVEF (Left Ventricular Ejection Fraction) — A measure of how well your heart pumps; monitored during your treatment
- Nadir — The lowest point of your blood counts, usually 7–14 days after a chemotherapy cycle
- Dysgeusia — Changes in how food tastes
- Gonadotoxicity — Damage to your ovaries or reproductive system from treatment
- DXA scan — A bone density test to check for osteoporosis
- Acupuncture — A complementary therapy using thin needles at specific body points; recommended in cancer guidelines for nausea, neuropathy, fatigue, joint pain, and hot flashes
- Electroacupuncture — A form of acupuncture that adds mild electrical stimulation to the needles
Key Takeaways
- Your side effects will vary depending on which chemotherapy drugs you receive, the dose, and your individual health.
- Most acute side effects are temporary and manageable with supportive medications and lifestyle adjustments.
- Prevention is key — take all your prescribed medications (especially antiemetics and growth factors) as directed.
- Exercise during chemotherapy is safe and strongly recommended — it reduces fatigue, preserves fitness, and may help with neuropathy and quality of life.
- Complementary therapies like acupuncture have guideline-level support for managing nausea, neuropathy, fatigue, joint pain, and hot flashes — ask your care team if acupuncture might be right for you.
- Report your symptoms early. Your care team can adjust doses, change medications, or provide treatments to help.
- Sexual health changes are common and treatable — do not hesitate to discuss them with your care team.
- Staying physically active, eating well, and maintaining your emotional well-being are important parts of your care during and after treatment.
- Your care team is here to support you through every step of your treatment and recovery.
Trusted Resources for More Information
- American Cancer Society — www.cancer.org — Comprehensive information on chemotherapy side effects, survivorship, and physical health, including sexual health. Helpline: 1-800-227-2345
- Cancer.Net (ASCO) — www.cancer.net — Patient information from the American Society of Clinical Oncology, including blogs, podcasts, and videos. Some content available in Spanish.
- National Cancer Institute — www.cancer.gov — Includes the "Facing Forward" series for life after treatment and "Eating Hints" for nutrition during and after treatment. Cancer Information Service: 1-800-4-CANCER
- NCCN Guidelines for Patients — www.nccn.org/patientresources/patient-resources/guidelines-for-patients — Free, plain-language versions of clinical guidelines, including a Survivorship guide
- Society for Integrative Oncology — integrativeonc.org — Information on evidence-based complementary therapies in cancer care, including acupuncture
- Cancer Support Community — www.cancersupportcommunity.org — Helpline: 1-888-793-9355, with online support groups and educational materials
- CancerCare — www.cancercare.org — Free professional support services including counselling, support groups, and educational workshops
- MedlinePlus — www.nlm.nih.gov/medlineplus/cancers.html — Accurate, current information organised by cancer site from the National Institutes of Health
- Bajpai, J., Kapu, V., Modi, J. et al. (2024) 'Acupuncture as a modality of treatment for chemotherapy-induced peripheral neuropathy in breast cancer: A phase 3 randomized controlled trial (ABC-CIPN)', Journal of Clinical Oncology.
- Hershman, D.L., Unger, J.M., Greenlee, H. et al. (2018) 'Effect of acupuncture vs sham acupuncture or waitlist control on joint pain related to aromatase inhibitors among women with early-stage breast cancer: A randomized clinical trial', JAMA, 320(2), pp. 167–176.
- Lu, W., Giobbie-Hurder, A., Tanasijevic, A. et al. (2024) 'Acupuncture for hot flashes in hormone receptor-positive breast cancer: A pooled analysis of individual patient data from parallel randomized trials', Cancer.
- National Comprehensive Cancer Network (2026) NCCN Clinical Practice Guidelines in Oncology: Survivorship. Plymouth Meeting, PA: NCCN.
- National Comprehensive Cancer Network (2026) NCCN Clinical Practice Guidelines in Oncology: Cancer-Related Fatigue. Plymouth Meeting, PA: NCCN.
- Shen, G., Ren, D., Zhao, F. et al. (2024) 'Effect of adding electroacupuncture to standard triple antiemetic therapy on chemotherapy-induced nausea and vomiting: A randomized controlled clinical trial', Journal of Clinical Oncology.
- Society for Integrative Oncology and American Society of Clinical Oncology (2022) Integrative medicine for pain management in oncology: Society for Integrative Oncology–ASCO guideline.
- Zhang, X.W., Hou, W.B., Pu, F.L. et al. (2022) 'Acupuncture for cancer-related conditions: An overview of systematic reviews', Phytomedicine, 100, 154118.

