Herceptin® Update
HERCEPTIN IN EARLY STAGE BREAST CANCER
- A STORY IN PROGRESS
As many as 800 New Zealand women per year are diagnosed with HER2 positive
breast cancer, a cancer that is generally more aggressive and has a poorer
outcome than other types of breast cancer. The relatively new drug Herceptin
offers these women a better chance of staying healthy for longer.
Although the issue has received a lot of media coverage over the last couple
of years, women with early stage breast cancer who may benefit from the
drug currently still have to pay up to about $70,000 themselves to get Herceptin
for a year as it is only funded for 9 weeks treatment. (Herceptin treatment
for advanced breast cancer is fully funded.) Learn more about Herceptin
and the efforts of New Zealand women with breast cancer to have it funded
in the submissions above and in Upfront Issues 65, 66, 69, 71, 73, 77.
Part I – Herceptin Offers Hope
HER2 is Human Epidermal growth factor Receptor 2 and is one of the growth factors that are important for controlling cell growth. It is present in small amounts in normal breast cells and breast cancer.HER2 positive (HER2+) breast tumours either have too many HER2 genes or produce large amounts of HER2 protein. The prognosis is poorer for the 25 to 30% of breast cancer patients who have such tumours – the cancer is more aggressive, growing more quickly and spreading more rapidly, there is a higher rate of recurrence and it is more invasive leading more often to metastases. Ten year survival rates are approximately 40%.
Recent research on trastuzamab (Herceptin) has offered hope for women with HER2+ breast cancer. Herceptin is not a drug, per se, but a monoclonal antibody – a molecularly engineered antibody that resulted from early research on mice. It is a targeted treatment that works on the cancer not healthy tissue and for that reason has benefits over conventional chemotherapy.
Herceptin works in three ways:
1. It binds to the HER2 proteins on the surface of the tumour cell and blocks signals for cell growth which may result in cancer cell death.
2. When it binds to the HER2 proteins on the surface of the tumour cell, immune system cells within the body recognise it as a foreign object and attack, helping to more effectively kill the cancer cells.
3. It can enhance the effectiveness of chemotherapy which attacks and damages the DNA in the nuclei of tumour cells and causes cancer cell death.
Generally the adverse effects of Herceptin are mild when compared with the toxic effects of chemotherapy. Side effects may include fever and chills, weakness, nausea, vomiting, cough, diarrhoea, and headaches, and are usually associated with the first dose and not subsequent doses. However, some women have experienced heart damage leading to congestive heart failure while on Herceptin. Recent research has found that most of the adverse cardiac effects of 12 months Herceptin treatment are treatable and reversible when Herceptin is not administered concurrently with anthracycline drugs. Results from recent clinical trials on Herceptin for early stage breast cancer have been received with enthusiasm by the medical profession and the breast cancer community. So far four large adjuvant Herceptin trials have been reported on: NSABP B31, NCCTG Trial, BCIRG006 Trial and the HERA Trial. Each is slightly different and the follow-up has been relatively short. Overall, some 13,000 women, including women from New Zealand, participated in the four trials.
The studies suggest that the three-year, disease-free survival rate will be 75.4% for those on conventional treatment, and 87.1% for those on Herceptin. Subtracting these numbers from 100, we obtain the advertised 50% improvement in disease-free survival rates (from 24.6% to 12.9%). But another way of looking at it is that about 12 out of every 100 users of Herceptin, or about three out of every 100 breast cancer patients, will be helped by the drug to remain disease-free after three years. This sounds less dramatic, though of course it is still very worthwhile.
Moving to life expectancy, Herceptin improves the chances of survival after three years from 91.7% to 94.3%. So the reduction in the death rate is indeed one-third (from 8.3% to 5.7%). But in less dramatic language, Herceptin keeps about three people out of every 100 alive after three years for those who take the drug. This amounts to less than one extra person per 100 among all breast cancer patients.” From Herceptin will work wonders, not miracles, Gavyn Davies, 1/06/06, Guardian.co.uk
An additional smaller trial (FinHer) undertaken in Finland has shown that just nine weeks of Herceptin improved disease-free survival at two-year follow-up. Some New Zealand women will have the opportunity to join the SOLD trial, which will compare 9 weeks treatment with 12 months. Together the trials have shown that the benefit of Herceptin is independent of chemotherapy and patient characteristics (eg: age, tumour grade and node involvement).
Other Herceptin® information:
Breast Cancer
Network submission to Pharmac June 2008
BCAC
submission to Pharmac June 2008
Herceptin® frequently asked
questions
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