Herceptin (Trastuzumab) for women with early breast cancer
Preliminary results from 3 trials were released at the ASCO conference in Orlando Florida, USA on May 16, 2005. These trials tested whether the antibody treatment Herceptin (trastuzumab) given after initial breast cancer treatment (surgery, radiotherapy and adjuvant chemotherapy) could further reduce the risk of cancer recurrence in women with a particular type of breast cancer. All 3 trials so far suggest that Herceptin (given weekly or every 3 weeks for 1 year) reduces the risk of cancer recurrence by about 50%.Background
About 20% of breast cancers are ‘HER 2 positive’, meaning a particular protein (HER 2) is present on the cells in large amounts. This can be tested for in major treatment centres in Australia. These breast cancers can be treated with Herceptin, and in women with advanced or metastatic breast cancer, Herceptin is a standard treatment in Australia.What the new studies tell us is that Herceptin can be used in early breast cancer after adjuvant chemotherapy has finished, to reduce the chance of cancer recurrence happening in the first place. One would expect that in the long run, this would reduce the chances of dying of breast cancer, and 2 of the 3 studies suggest that this is true. The results of the third study are not mature enough to show this yet.Serious side-effects appear to be very uncommon (less than 1% risk), but this requires further study. It is known that some women on Herceptin can develop heart problems (such as heart failure), and routine heart tests are recommended. The treatment needs to be given by intravenous infusion over about 2 hours.
What’s next?
Although very exciting, these results are still preliminary, and there is no information about long term side-effects. The treatment is also extremely expensive and it may be some time before government funding is available. Herceptin will remain available in Australia for any woman where breast cancer has spread (metastases). If funding solutions can be found, adjuvant Herceptin could be considered for those women with ‘HER 2’ positive cancer and high risk features, such as a number of involved lymph nodes.
| Disease free survival (DFS) | Distant disease free survival (DDFS) | Overall survival | |
| %2 year result | 86% vs 77% | 87% vs 79% | 96% vs 95% |
| % difference (absolute) | 9% | 8% | 1% |
| Statistically significant | yes (P< 0.0001) | yes (P< 0.0001) | no (p=0.26 |
| Definition | Major events which are scored in this calculation are recurrence in the breast (after breast conservation), the chest wall (after a mastectomy), disease which occurs in the glands (such as those in the arm pit and glands above the collar bone), disease that spreads in other places (such as in the bone or lung), disease which occurs in the opposite breast, cancer of another type (for example colon cancer or ovarian cancer) which have nothing to do with the breast cancer and death from any cause (breast cancer and non breast cancer) | Includes disease which occurs in other parts of the body. For example in the bone or liver, disease in the other breast and second malignancies but excludes disease which recurrs in the breast or chest wall or nearby glands and a death from another cause. | An event here is defined as a death (from either breast cancer, complications of treatment or another cause) |
| Comment | Disease free survival measures 'everything' and is not very 'sensitive'. Many oncologists find this figure a 'softer' statistic as it includes every major 'event' related or un-related to breast cancer. | This statistic is more relevant and statistically improvements in distant disease free survival are translated many years later to improvements in over all survival. | This is ultimately the best end point in determining whether a treatment simply delays recurrence or whether it improves overall cure rates. At this stage there is no difference between the treatment arm which includes Herceptin and the control arm which does not include Herceptin. However, the data is only 2 years old and the large differences is distant disease free survival of 8% are likely to be translated to an improvement in overall survival of approximately 3-4% in the longer term, however, this still remains speculative. |
| Relative | 46% | 49% | 26% |