HER2-positive breast cancers tend to be more aggressive than HER2-negative breast cancers. Two studies found that even small (1 cm or smaller), early-stage, HER2-positive breast cancers are more likely to come back (recur) and spread to parts of the body away from the breast (metastasize) than small, early-stage, HER2-negative breast cancers.
The results suggest that treating small, early-stage, HER2-positive breast cancers with the targeted therapy medicine Herceptin (chemical name: trastuzumab) may make sense.
HER2-positive cancers make too much of the HER2 protein. The HER2 protein sits on the surface of cancer cells and receives signals that encourage cancer to grow and spread. About one out of every four breast cancers is HER2-positive.
Herceptin works by attaching to the HER2 protein and blocking it from receiving growth signals. By blocking the signals, Herceptin can slow or stop the growth or spread of the cancer.
Treating HER2-positive, early-stage breast cancer with Herceptin after surgery has been shown to lower the risk of recurrence. Current treatment guidelines recommend using Herceptin only when the cancer is larger than 1 cm because the risk of recurrence is higher for cancers of that size. The guidelines do say that using Herceptin to treat smaller cancers may be considered.
In these studies, the researchers compared the outcomes of two groups of women. All the women were diagnosed with small (1 cm or smaller), early-stage breast cancer that hadn't spread to lymph nodes. One group of women was diagnosed with HER2-positive cancer and the other group with HER2-negative cancer. None of the women were treated with Herceptin.
The researchers found:
- 10% to 23% of women diagnosed with small, HER2-positive cancer had a recurrence within 5 years of diagnosis compared to about 5% of women diagnosed with HER2-negative cancer.
- Women diagnosed with small, HER2-positive cancer were 5 times more likely to have a metastatic recurrence -- the cancer coming back some place else in the body -- compared to women diagnosed with HER2-negative cancer.
Based on these and other results, the researchers said that doctors should consider using Herceptin to treat smaller, early-stage, HER2-positive breast cancers after surgery to lower the risk of recurrence. One researcher estimated that the number of women who had a recurrence would be reduced by 4% to 5% if Herceptin were used to treat these smaller, early-stage, HER2-positive cancers.
Herceptin can cause side effects, some of them serious. It's also expensive compared to some other cancer medicines. Because of these concerns, some doctors suggest only using Herceptin to treat small, HER2-positive cancers with specific "personality" factors. One suggestion is to use Herceptin only if the cancer is 0.5 cm or larger. Another is to give Herceptin for a shorter time than is done with larger cancers: 6 months instead of 12 months, for example.
While these results are promising, the official Herceptin treatment guidelines haven't been changed. Still, using Herceptin to lower the risk of recurrence for some smaller, early-stage, HER2-positive breast cancers is currently an option that can be considered.
If you've been diagnosed with early-stage, HER2-positive breast cancer and your doctor isn't recommending Herceptin treatment, you might want to ask why. The treatment recommendation may be based on the size of the cancer and because it hasn't spread to any lymph nodes. If those are your doctor's reasons, you may want to ask your doctor about these results and whether using Herceptin after surgery might make sense for you.
Learn more about Herceptin in the Breastcancer.org Targeted Therapies section.