Breast Cancer — NZ Condition Guide | KiwiMeds

What is Breast Cancer?

Breast cancer is the most common cancer in New Zealand women, with around 3,500 new cases per year. It can also occur in men (around 25 cases per year). Most breast cancers are treatable, especially when detected early through screening.

Overview

Breast cancer symptoms include a new lump or thickening in the breast or armpit, change in breast size or shape, dimpling or puckering of the skin, nipple changes (inversion, discharge, rash), and persistent pain in one area. However, many breast cancers are found through screening mammograms before symptoms develop. BreastScreen Aotearoa offers free mammograms every two years for women aged 45–69. Women over 70 can also access screening but must self-refer.

Treatment in New Zealand

Breast cancer treatment depends on the type and stage. It may include surgery (lumpectomy or mastectomy), radiation therapy, chemotherapy, hormone therapy (tamoxifen — funded by Pharmac — or aromatase inhibitors for hormone receptor-positive cancers), and targeted therapies (trastuzumab/Herceptin for HER2-positive cancers — Pharmac-funded). Most women with early breast cancer do very well with treatment.

NZ-Specific Information

BreastScreen Aotearoa provides free mammography screening for eligible women. Breast Cancer Foundation NZ (breastcancerfoundation.org.nz) provides information, support, and funds research. Māori and Pacific women have lower screening participation and worse outcomes — culturally safe screening is a priority. Pharmac funds the major breast cancer treatment agents.

Frequently Asked Questions

Should I do regular self-examination? While formal monthly self-examination is no longer specifically recommended, being breast aware — knowing how your breasts normally look and feel, and reporting changes — is important. Does breast cancer run in families? Around 5–10% of breast cancers are hereditary (BRCA1/BRCA2 genes). Genetic testing is available if you have a strong family history.

Supplements That May Support Management

⚠️ Important: The supplements listed below have varying levels of clinical evidence. They are not a substitute for prescribed medications and should only be considered as adjunctive support under the guidance of a qualified healthcare professional. Always inform your GP or pharmacist before commencing any supplement, as interactions with prescribed medicines are possible.

• Vitamin D — Vitamin D deficiency is associated with increased breast cancer risk and worse prognosis. Supplementation is recommended where deficiency is confirmed. Vitamin D receptors in breast tissue modulate cell proliferation and differentiation.
• Omega-3 Fatty Acids — Higher dietary and supplemental omega-3 intake is associated with reduced breast cancer risk and improved prognosis. Omega-3s reduce tumour-promoting inflammatory eicosanoids and inhibit cancer cell proliferation in preclinical models.
• CAUTION: Soy isoflavones during active treatment — The safety of soy isoflavone supplements during oestrogen-receptor-positive breast cancer treatment (particularly with tamoxifen or aromatase inhibitors) remains debated. Moderate dietary soy (1–2 servings/day) appears safe, but high-dose isoflavone supplements should only be taken with oncologist approval.
• Vitamin C (IV high-dose — medical administration only) — High-dose intravenous vitamin C as an adjunct to chemotherapy is being studied. At pharmacological (IV) doses, it acts as a pro-oxidant selectively toxic to cancer cells. This is a medical procedure, not a supplement recommendation.
• Melatonin — Melatonin has demonstrated anti-proliferative and anti-oestrogenic effects in ER-positive breast cancer cell lines. Some evidence supports its use as an adjunct to endocrine therapy, with oncologist approval.

Relevant Vaccinations

Individuals living with breast cancer may benefit from the following vaccinations. Please discuss your vaccination status with your GP or practice nurse, as eligibility and funding through the New Zealand National Immunisation Schedule may apply.

• Influenza (annual) — Strongly recommended for all women with breast cancer, particularly those on immunosuppressive chemotherapy or targeted therapies.
• Pneumococcal — Recommended during and after chemotherapy due to immune compromise.
• COVID-19 — Women on active breast cancer treatment have compromised immunity. Maintaining up-to-date COVID-19 vaccination — with oncologist guidance on timing relative to treatment cycles — is strongly recommended.
• Shingles (Shingrix) — Recommended for women ≥50 years on immunosuppressive breast cancer treatments.
• HPV (if age-eligible) — HPV vaccination is recommended as part of comprehensive preventive health in women within eligible age ranges.

Dietary Guidance

Evidence-based dietary modifications play a meaningful role in the management of breast cancer. The following foods are generally recommended as part of a balanced, condition-appropriate diet. A referral to a registered dietitian may be beneficial for personalised nutritional planning.

• Cruciferous vegetables (broccoli, kale, cauliflower) — Sulforaphane and indole-3-carbinol support detoxification of oestrogen metabolites and demonstrate anti-proliferative breast cancer activity.
• Berries and colourful fruits — Rich in antioxidants (ellagic acid, anthocyanins) with anti-cancer and anti-inflammatory properties.
• Moderate dietary soy (tofu, tempeh, edamame) — Observational evidence from Japanese and Chinese women and survivor cohorts supports that 1–2 servings/day of whole soy foods does not increase recurrence risk and may be protective. This refers to whole foods, not high-dose isoflavone supplements.
• Flaxseed (ground) — Provides lignans (phytoestrogens) and alpha-linolenic acid. Evidence supports modest lignan intake as protective in ER-positive breast cancer when consumed in whole food form.
• Limit: alcohol (especially for ER-positive) — Alcohol is one of the most established dietary breast cancer risk and recurrence factors. Even moderate alcohol consumption increases ER-positive breast cancer risk. Minimising or eliminating alcohol is strongly recommended.

Related Conditions & Medications

Related conditions: Cervical Cancer, Ovarian Cancer.