Targeted Drug Therapy
Like chemotherapy, targeted therapies are drug therapies, but they are often given over a longer period of time.
These medicines are different from most chemotherapy drugs because they attack specific elements of the cancer cells and are less likely to harm normal cells.
There are two main targeted therapy drugs available in New Zealand at the moment (see below). However, new targeted therapies are being developed all the time and clinical trials are under way to investigate the effectiveness of these newer drugs.
Many targeted therapy drugs are given intravenously and you may have a special device called a port-a-cath inserted into your chest wall or arm to help medical staff give these drugs easily on a regular basis. This will save a nurse having to find a vein in your arm or hand each time you need treatment.
Targeted therapies available in New Zealand are:
Herceptin (generic name: trastuzumab). This drug is used in women with HER2-positive breast cancer and works by blocking the chemical signals that tell this type of cancer cells to grow.
It is given by injection over a 12-month period and is now fully subsidised in New Zealand, thanks to a prolonged campaign by BCAC and others. BCAC suggests that all women ask their oncologists to follow the evidence-based New Zealand and international guidelines for this medicine and opt for a 12-month treatment programme, rather than a 9-week treatment programme which is sometimes offered.
Side-Effects: Herceptin is usually extremely well tolerated with any side effects very rare. Very few women may experience result in flu-like symptoms, but these should become less severe as your treatment programme progresses.
In some cases, Herceptin can cause heart problems. This can range from very mild heart damage which results in no symptoms to more serious problems and in rare cases heart failure. Your doctor will discuss these issues with you and monitor your heart during your treatment programm. If you experience shortness of breath or heart palpitations let your doctor know immediately.
Tykerb (generic name: lapatinib). This drug is given in pill form and fights Her2-positive breast cancer by attacking the HER2 protein at a different site to Herceptin. Clinical trials have shown lapatinib to be beneficial in advanced HER2-positive breast cancer and trials are now under way to discover how effective it is in treating early breast cancer. This drug is not registered for the treatment of early stage HER2-positive breast cancer.
Side-Effects: The side effects associated with Tykerb tablets are usually mild. The most common side effects are diarrhea, skin rash, vomiting and fatigue. Dosages can be adjusted to ease these problems. In rare cases Tykerb can result in minor heart damage.
Click here for a fact sheet on Tykerb.
Perjeta (generic name: pertuzumab). This drug is used in patients with HER2-positive breast cancer and works to inhibit different proteins that cause HER2-positive breast cancers to grow. Results from the clinical trial (CLEOPATRA study) which were reported in October 2014 showed an extraordinary survival benefit of 15.7 months longer than patients who did not receive the drug. This drug is available in New Zealand and it is Medsafe registered. From 1st January 2017 Perjeta is now funded for many HER2-postive metastatic breast cancer patients. However, BCAC made a further joint submission with the Breast Cancer Foundation New Zealand to PHARMAC to re-consider the criteria for the funding of Perjeta and strongly urged PHARMAC to extend funding for this medicine to all patients currently being treated with trastuzumab for metastatic breast cancer.
Click here for a fact sheet on Perjeta.
Kadcyla (generic name: trastuzumab emtansine). This drug is used in patients with HER2-positive advanced (or metastatic) breast cancer who have received prior therapy with trastuzumab and a taxane within the adjuvant setting and who relapsed within 6 months of completing the therapy. It combines a chemotherapy drug, (DM1) that disrupts cell division, growth and functioning, with Herceptin. Latest results from the international clinical trial EMILIA show patients receiving Kadcyla had a median overall survival benefit of 10.8 months longer than those in the control arm of the study. This drug is available (but not publicly funded) in New Zealand and it is Medsafe registered. Roche supplies Kadcyla and it has a patient access programme for the drug. See more information here http://cancerinfo.co.nz/accessing-treatment/funding-medicines
Click here to read a fact sheet on Kadcyla.
Targeted therapies in the clinical trial phase:
PARP Inhibitors These are a new form of drug, which are currently being tested in clinical trials, so they are not yet approved for general use. However, these trials are showing promising results, especially for women with hereditary breast cancer caused by mutations to the BRCA1 and BRCA2 genes.
A PARP is an enzyme which repairs damage done to our DNA, but it also repairs cancer cells damaged by chemotherapy drugs. The “PARP inhibitor” drugs stop the PARP enzyme from repairing damaged cancer cells and thus allow chemotherapy drugs to work more effectively.
Several PARP inhibitors have been tested in clinical trials, but none is available for general use.