Roche Korea obtained additional indication approval for Kadcyla (ingredient: trastuzumab emtansine), a HER2 positive breast cancer drug for metastatic breast cancer, to be used for early breast cancer as well, in August last year.
The faster-than-expected grant was based on a study that showed the drug, as postoperative adjuvant therapy, reduced the risk of recurrence by 50 percent, compared to the existing standard treatment Herceptin (ingredient: trastuzumab).
Korea Biomedical Review recently met with Professor Jeong Joon of the Surgery Department at Gangnam Severance Hospital to learn how physicians treat HER2 positive early breast cancer patients before and after surgery, and how Kadcyla will affect the treatment of local breast cancer patients.
|Professor Jeong Joon of the Surgery Department at Gangnam Severance Hospital speaks during an interview with Korea Biomedical Review.|
Question: What are the overall characteristics of local breast cancer patients?
Answer: The number of patients with early detection of breast cancer has increased significantly. According to data at the Korean Breast Cancer Society, almost 60 percent of patients are in stage 0 or stage 1. In general, we regard breast cancer up to stage 2 as early breast cancer. Considering the ratio of patients with stage 0 to 2, 90 percent of all breast cancer patients are early breast cancer patients.
Q: How many patients with early breast cancer are diagnosed with HER2 positive?
A: HER2 positive breast cancer patients account for about 20 percent of all breast cancer patients. This proportion does not change depending on the stage. The proportion has been confirmed by various studies not only in Korea but in other countries.
Q: In Korea, what kind of treatments do HER2 positive early breast cancer patients receive before and after surgery?
A: In the past, preoperative adjuvant therapy was not active. So, doctors performed surgery first and chemotherapy, if necessary, or radiation therapy depending on the disease progression. Recently, however, preoperative adjuvant therapy treatment has become popular. Now, a doctor makes a comprehensive judgment of the patient's test results before surgery. If he or she determines that anticancer treatment should come first, the doctor then provides preoperative adjuvant therapy.
Usually, we look at a variety of factors, including stage and carcinoma properties. HER2 positive patients are subject to preoperative adjuvant therapy, including targeted therapy, if their tumor size exceeds 1cm. HER2 positive breast cancer patients have many targeted treatment options, and the current treatment regimen is that the targeted therapy and chemotherapy are used together.
Q: We heard that one of the reasons for deciding on an anticancer treatment before surgery is to increase the rate of pathological complete remission (PCR). Why is PCR important in early breast cancer treatment?
A: Assuming that other conditions are similar, patients who achieved pCR through preoperative adjuvant therapy have a better prognosis than those who did not. For example, if two patients are in the same cancer stage and have similar tumor size or lymph node metastasis, the prognosis of the patient who showed PCR is better than that of the other.
According to one study, patients with early breast cancer who showed PCR improved event-free survival by 52 percent and overall survival by 64 percent. The subgroup analysis showed that the event-free survival of patients with HER2 positive early breast cancer improved by up to 61 percent. It was a noticeable difference. Therefore, we can say that PCR has become more critical.
Q: If so, what kind of treatment will patients with PCR and those without it receive after that?
A: In the past, patients received therapies regardless of PCR. However, the KATHERINE study results on Kadcyla as postoperative adjuvant treatment changed the treatments. In the study, patients with HER2 positive early breast cancer, who underwent adjuvant therapy and surgery, were treated with Kadcyla, and their prognosis improved significantly, compared to the standard therapy (trastuzumab).
While invasive disease-free survival (iDFS) of the standard therapy-treated patients in the third year was 77 percent, the Kadcyla group’s iDFS improved up to 88.3 percent. In terms of absolute value, the difference is 11 percentage points, but at a risk ratio, 50 percent was improved. This means that the risk of recurrence was halved.
In early breast cancer treatment, it is not easy to improve the treatment performance this much, compared to the standard therapy. This is a meaningful clinical improvement. With Kadcyla treatment, it is possible to significantly reduce the risk of recurrence in high-risk patients who did not have PCR after adjuvant therapy and surgery.
Q: How will Kadcyla's study results affect the treatment of domestic patients with early breast cancer?
A: The drug can contribute to improving their treatment conditions. In Korea, many breast cancer patients are in their 40s and 50s. The average onset age is about 51 years old. For many women in their late 40s and early 50s, it is the time that they try to have their own life just after sending their children to college, and they are often working. Therefore, breast cancer that frequently occurs in this age group is a problem for both individuals and society. Its impact on the family is also powerful. Breast cancer in this age group has a different social impact from that of other cancer, which is common in people over 70.
Kadcyla is an antibody-drug conjugate (ADC). It can be used as monotherapy, without the need for concomitant chemotherapy. The drug does not cause many side effects, so patients can continue their social life while receiving Kadcyla therapy.
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