In many cases additional treatment is required after surgery. This is called adjuvant therapy. The adjuvant treatment for breast cancer may include chemotherapy, hormonal therapy, radiotherapy or immunological therapy. Usually a combination of the above is administered. The objective of adjuvant treatment is to destroy residual cancer cells circulating in the body, preventing them from lodging in organs and giving rise to distant metastases. Currently there are no means to identify these circulating cancer cells, but based on a number of the characteristics of breast cancer the probability of recurrence or metastases can be estimated. From large international clinical studies, we know that chemotherapy and hormonal therapy can reduce the risk of relapse and death from breast cancer by 30-40%.
- hormonal therapy
Adjuvant hormonal therapy
Some tumor cells contain receptors for the female hormones estradiol and progesterone. Administration of these hormones to cancer cells may stimulate the growth of these cells. In menopausal women with breast cancer more than 80 % of tumors are hormone-sensitive. Removing hormonal stimuli to such breast cancer cells reduces the growth of these tumors. Therefore, women with hormone-sensitive tumors should take ‘anti-hormonal’ treatment. These disrupt the function of hormones and thus increase the chance of successful treatment. This means that the chances of survival are improved. This form of treatment consists of tablets that should be taken for at least 5 years. New evidence from large clinical trials shows that a longer intake corresponds to an even better survival. There are a variety of hormonal treatments:
Elimination of ovarian function: This is obviously only in pre-menopausal women, as following the menopause, ovarian function falls naturally. Ovarian function can be eliminated by surgical removal, by irradiation or by administering drugs.
Blocking the influence of hormones on breast cancer: By blocking cell receptors with anti-hormones, such as tamoxifen, the growth stimulating effect of female hormones are suppressed. Tamoxifen was a breakthrough in the treatment of breast cancer. It decreases the likelihood of relapse by 45% and is generally well tolerated.
Preventing the conversion of androgens into estrogens: Another source of estrogens is the conversion of androgens (male hormones) to estrogens in peripheral tissues of the body (e.g. muscle and fat), influenced by a specific aromatase enzyme. Through the so-called aromatase inhibitors this conversion can be prevented, so that estrogen is no longer formed in peripheral tissues. This can only be used in postmenopausal women, where ovarian function has already stopped.
In general, hormonal treatment is well tolerated. Adverse reactions are primarily caused by the loss of circulating female hormones. These include; hot flushes, muscle and joint aches, joint stiffness, depression, lethargy, sexual problems (such as vaginal dryness, painful intercourse and decreased libido), a slightly increased clotting tendency, with a corresponding increased rate of thromboembolism and a slightly increased risk of cervical cancer and osteoporosis.
Chemotherapy is widely used in the treatment of breast cancer. Typically, it is administered intravenously, although in recent years some oral medication is also available. The treatment is repeated at regular intervals, for example every 3-4 weeks, in a certain number of cycles, e.g. 6.
It is important that the correct dose is given at the right time. This dose is determined by the patient’s surface area, which is calculated from their height and weight. With very large weight changes the dose may need to be adjusted.
Usually a combination of chemotherapeutic agents is employed. This combination is chosen to improve efficiency, without significantly increasing side effects.
Cytotoxic chemotherapy interacts with the genetic material of cancer cells and prevents their division and tumour growth. Since it works mainly on rapidly dividing cells, chemotherapy also affects other rapidly dividing tissues, causing a number of side effects. However, healthy cells have a greater resistance to the effects of chemotherapy and the net result is a reduction in tumour volume.
The main side effects of chemotherapy are:
- Nausea and vomiting
- Bone marrow suppression
- Hair loss and nail abnormalities
- Local skin reactions at the injection site
- Changes to the menstrual cycle with resultant effects on fertility
- Cystitis and urine discoloration
- Specific organ toxicity (heart, lungs, liver, kidneys and nervous system). This toxicity is highly specific to a select number of agents. Your doctor will advise you on any risks in relation to your body surface area, general medical condition and associated disease processes. Sometimes it is necessary to reduce the dose of certain agents or avoid them.
For many patients, chemotherapy is still a difficult process. The side effects are not always well tolerated. However, in recent years, many new cytotoxic agents have been introduced to the market with fewer side effects or effects that can be adequately treated or prevented. It is important that you discuss each side effect you encounter with your oncologist.
Neoadjuvant or ‘preoperative’ chemotherapy is used for large breast tumours, where breast-conserving surgery is initially not possible. The circulating neoadjuvant chemotherapy kills the cancer cells, and thus reduces the risk of relapse. One additional advantage is that the likelihood of breast conservation increases. Following surgery, further chemotherapy is usually not required.
Radiotherapy is administered after breast-conserving surgery, or after a mastectomy for large tumors, to reduce the risk of local recurrence. The axilla can also be irradiated if there is significant lymph node involvement.
Radiotherapy treatment is usually given daily and lasts for 5-7 weeks.
The most frequent side effects of radiotherapy are; fatigue with redness or burns of the skin. Permanent skin discoloration is also common. With irradiation of the axilla, there is an increased risk of lymphedema in the arm.
After a few months and up to several years following radiotherapy, local fibrosis may occur, making the breast feel hard.
In 20-25% of all breast cancer patients the HER-2/neu or c-erbB-2 receptors are present on tumor cells. Blocking these receptors using an antibody, trastuzumab, inhibits cell growth and results in cell death.
Trastuzumab decreases breast cancer relapse by an estimated 50%. This treatment also has fewer side effects because it specifically targets cancer cells.
A number of studies are currently being performed on additional types of immunotherapy.