Decision aid

Breast cancer — risk-reducing medicine and radiotherapy decisions

By Dr HB Lo, FACRRM 4 min read

General information to help you prepare for your GP — not a diagnosis, not personal medical advice. It doesn't replace a consultation, and using it doesn't create a doctor–patient relationship.

Two breast-cancer decisions are genuinely preference-sensitive — the "right" answer depends on how you weigh the trade-offs. The first is whether to take a risk-reducing medicine if you're at high risk. The second is whether to have radiotherapy after breast-conserving surgery.

For high-risk women, medicines like tamoxifen can roughly halve the chance of developing breast cancer, but carry their own risks. After breast-conserving surgery, radiotherapy substantially lowers the chance of the cancer returning — and is standard — yet some lower-risk older women may reasonably leave it out.

This guide explains how each is weighed, so you can take clear questions to your GP and breast team.

Two decisions where your own weighing matters most

Breast cancer care involves a lot of decisions, and many of them have a clear medical default. But a couple are genuinely preference-sensitive — meaning the right answer depends on how you weigh the trade-offs, not only on what the evidence says works. Those are the ones worth slowing down for, because they’re where your values, and a good conversation, actually change the outcome.

This guide covers two of them: whether to take a risk-reducing medicine if you’re at high risk of breast cancer, and whether to have radiotherapy after breast-conserving surgery. Both are decisions made with your GP and breast cancer team — this is general information to help you prepare for those conversations, not a recommendation about your own treatment.

Risk-reducing medicines — for women at high risk

If you’ve been identified as being at increased or high risk of breast cancer — often through family history or other risk factors — there are medicines that can lower that risk before any cancer develops. As Cancer Australia sets out, options include tamoxifen, and — for women past menopause — raloxifene or an aromatase inhibitor such as anastrozole. Taken daily over several years, these can reduce the chance of developing breast cancer by roughly a third to a half, depending on the medicine and the situation.

The counterweight is real. Tamoxifen, for example, carries a small increased risk of blood clots and of cancer of the uterus lining, per Cancer Australia. So this is a true trade-off, and how it lands depends heavily on how high your starting risk is: the higher your risk, the more an effective preventive medicine shifts it. The honest move is to see the benefit and the downsides at their real sizes for you specifically. The risk-reducing medicine decision aid below is built to help you prepare that conversation — it doesn’t tell you to take or avoid anything.

Radiotherapy after breast-conserving surgery — the usual default

Breast-conserving surgery (a lumpectomy or wide local excision) removes the cancer while keeping the breast. For most women with early breast cancer, the standard next step is radiotherapy to the remaining breast, because it substantially reduces the chance of the cancer returning there, per Cancer Australia and Breast Cancer Network Australia.

This pairing is well established: breast-conserving surgery followed by radiotherapy gives the same survival as removing the whole breast for most women with early disease, as Cancer Australia explains. So for the great majority, radiotherapy after a lumpectomy is the recommended default, and the decision is straightforward.

When omitting radiotherapy can be a reasonable option

There is, however, a specific lower-risk situation where leaving radiotherapy out is a reasonable option to discuss. For some women over about sixty-five with small, hormone-receptor-positive, node-negative cancers who take hormone (endocrine) therapy, omitting radiotherapy has been found to be safe in the important sense that it doesn’t reduce overall survival — though it does increase the chance of the cancer returning in that breast, per the RACGP.

That’s a genuine trade-off: less treatment burden, against a higher local recurrence risk. It’s a careful, individual conversation with your radiation oncologist and breast team — not a general rule, and not something to assume applies to you. The radiotherapy-after-breast-conserving-surgery decision aid below helps you understand the trade-off and prepare the questions.

The hormone (endocrine) therapy that often sits alongside

Both decisions above often sit next to a third: hormone-blocking (endocrine) therapy. If your breast cancer is hormone-receptor-positive, this is usually recommended after surgery to lower recurrence, as Cancer Australia and Breast Cancer Network Australia describe. Which medicine suits depends on menopausal status — tamoxifen can be used at any age, aromatase inhibitors for women past menopause — and it’s typically a daily tablet for five to ten years, with benefit that continues after the course ends, per Therapeutic Guidelines.

It’s worth understanding how these pieces fit, because the radiotherapy decision in older lower-risk women specifically assumes endocrine therapy is being taken.

A multidisciplinary, shared decision

Across all of this, the same point holds: these are decisions made with a multidisciplinary breast cancer team — surgeon, oncologists, breast care nurse — weighing your tumour’s features, your age and health, and your own preferences, as Cancer Council Australia, HealthDirect and the Better Health Channel all emphasise. Second opinions and breast care nurse support are part of the process, not an imposition on it.

The questions worth taking in

  • Given my actual level of risk, how much would a risk-reducing medicine change it — and what are its downsides for me?
  • Is radiotherapy the clear recommendation after my surgery, or am I in a situation where omitting it is reasonable to discuss?
  • If I’m offered hormone therapy, which one suits me, and for how long?
  • Who’s on my breast cancer team, and can I get a second opinion if I’d like one?

These are questions, not conclusions. The aim is to decide with your team.

What this is, and is not

This is general information to help you prepare for your GP and breast cancer team — not a diagnosis, and not personal medical advice. It doesn’t tell you to start, stop or change any treatment; those decisions are made with your own doctors, who can weigh your specific cancer and history. For trustworthy Australian background, see Cancer Australia and Breast Cancer Network Australia.

Related on this site: the breast lump and breast screening explainer covers finding and assessing a lump, the cancer screening decision aid sets out the screening choices, and the menopause and HRT decision aid is relevant if treatment has brought on menopausal symptoms.

If you want a thorough, unhurried discussion to help you prepare for these conversations, you can work with Dr Lo.

Author: Dr Hoe Bing Lo — AHPRA MED0001212640 · FACRRM. Fun Doctors Pty Ltd · ABN 83 404 436 330.

Tools to take to your GP

Each runs in your browser — nothing you enter is stored or sent anywhere. They help you prepare the questions and print a one-page summary to bring to your appointment. They don't diagnose or recommend a specific treatment.

Frequently asked questions

  • I'm at high risk of breast cancer — can a medicine lower my risk?

    For some women at increased risk, yes. Risk-reducing (preventive) medicines such as tamoxifen — and, for women past menopause, raloxifene or an aromatase inhibitor like anastrozole — can meaningfully lower the chance of developing breast cancer, by roughly a third to a half depending on the medicine and situation. But they aren't free of downsides: tamoxifen, for instance, carries a small increased risk of blood clots and of cancer of the uterus lining. So it's a genuine trade-off and a personal decision, weighed with your doctor against your individual level of risk.

  • Is taking a preventive medicine a clear yes if I'm high-risk?

    Not automatically — it's preference-sensitive. The benefit depends on how high your risk actually is: the higher your starting risk, the more an effective preventive medicine shifts it. Against that you weigh the side effects and small risks of the medicine itself, taken daily over several years. Two women at similar risk can reasonably reach different decisions. The honest approach is to see the benefit and the downsides at their true sizes for you specifically — which is exactly what to work through with your GP and specialist.

  • Do I definitely need radiotherapy after a lumpectomy?

    For most women with early breast cancer, radiotherapy after breast-conserving surgery is standard and strongly recommended — it substantially reduces the chance of the cancer coming back in that breast, and breast-conserving surgery plus radiotherapy gives the same survival as removing the whole breast. So the default for most people is yes. There are, however, selected lower-risk situations where leaving it out is a reasonable option to discuss — see below. It's a decision made with your breast cancer team based on your specific tumour.

  • I've heard some older women can skip radiotherapy — is that true?

    In a specific, lower-risk group, it can be a reasonable option. For some women over about 65 with small, hormone-receptor-positive, node-negative cancers who take hormone (endocrine) therapy, omitting radiotherapy has been found to be safe in the sense that it doesn't reduce overall survival — though it does increase the chance of the cancer returning in that breast. So it's a trade-off: less treatment burden, against a higher local recurrence risk. This is a careful, individual conversation with your radiation oncologist and breast team, not a general rule.

  • What's hormone (endocrine) therapy, and how long is it taken?

    If your breast cancer is hormone-receptor-positive, hormone-blocking (endocrine) therapy is usually recommended after surgery to lower the chance of recurrence. Which medicine suits depends on whether you've been through menopause: tamoxifen can be used at any age, while aromatase inhibitors work for women past menopause. It's typically taken as a daily tablet for five to ten years, and its protective benefit continues even after you finish the course. The specifics are decided with your oncologist.

Source quality

Sources grouped by evidence tier. Australian primary tier first; international where Australia is silent or lagging. How tiers work.

If you want a thorough, unhurried work-up of your own — not a generic answer — you can work with Dr Lo.

Author: Dr Hoe Bing Lo · AHPRA MED0001212640 (verify)

General health information drawn from current Australian guidelines and primary trial data. Not personal medical advice. Always consult your own GP for diagnosis, treatment, or referral specific to you. See full disclaimer.

Last reviewed: 15 June 2026