Study Finds Patients with HER2+ Breast Cancer Live Longer if Anti-Cancer Drugs Induce pCR

Final analysis results from the randomized NeoALTTO BIG-06 clinical trial, which evaluated lapatinib (Tykerb) and trastuzumab (Herceptin) given before surgery in patients with early HER2-positive breast cancer, has revealed that women who had a pathological complete response (pCR) survived longer without the cancer returning than those who did not.

In addition, the study found this was more likely to happen in patients who received the 2 anti-cancer drugs together, rather than as single agents. The 9-year survival data was presented at the 12th European Breast Cancer Conference.

"Patients who achieved a pCR had significantly better long-term survival compared to those who did not achieve pCR,” principal investigator Paolo Nuciforo, MD, of the Vall d’Hebron Institute of Oncology in Barcelona, Spain, said in a presentation of the data. Although overall survival rates did not differ significantly between the three treatment groups, nearly twice as many patients achieved pCR if they received both drugs, 51% compared to 27.1% of patients receiving only one drug in the other two arms of the study combined."

Overall, the study enrolled 455 women with early HER2-positive cancer to receive either neoadjuvant trastuzumab or lapatinib alone or in combination. Following surgery, the study participants were given 3 cycles of chemotherapy followed by 34 weeks of whichever therapy they had originally been randomized to receive.

With a median follow-up of 9.7 years, event-free survival (EFS) was observed in 69% of the patients receiving both drugs, 65% of the trastuzumab-only group, and 63% of the lapatinib-only group. However, these differences were not deemed to be statistically significant.

Moreover, overall survival (OS) rates were 80% in the combination group, 77% in the lapatinib group and 76% in the trastuzumab group, with no statistically significant differences between the groups.

When women who had achieved pCR were compared with those that had not across all 3 treatment groups, researchers found that EFS and OS were significantly better in women who had pCR, with 77% of patients who achieved pCR surviving 9 years event-free compared to 61% of patients who did not achieve a pCR. Further, 88% of patients who achieved pCR were still alive at 9 years compared to 72% of patients who did not.

Subgroup analysis demonstrated that these associations were statistically significant in women who received the drug combination or those who were hormone receptor (HR)-negative.

"Although we might have expected a significantly higher overall survival in the group of women receiving the combination of lapatinib and trastuzumab where pCR rates were higher, this was not the case. This was possibly due to the fact that the study was not powered to detect small differences in survival between the three groups,” Nuciforo explained.

"The results from this analysis show that patients who achieve pCR are significantly more likely to survive for longer than those who do not achieve pCR. This validates pCR as an early indicator of long-term outcome for HER2-positive disease and could help doctors decide on the best treatment,” Nuciforo added. “On one hand, patients not achieving a pCR may be at higher risk of recurrence and giving extended therapy to them could potentially lower this risk. On the other hand, those patients who do achieve pCR could be spared additional toxic treatments.”

Currently, all women with HER2-positive breast cancer receive toxic adjuvant chemotherapy after anti-HER2 neoadjuvant treatment to reduce the risk of recurrence after surgery; However, not all women have the same risk.

With the current study in mind, Nuciforo explained that moving forward, if we could predict which patients are at high risk of their cancer recurring, providers could give more aggressive adjuvant therapies only to those who need it and not to those who have achieved pCR and are at low risk of recurrence.

Reference:

HER2+ breast cancer patients live longer if drugs given before surgery eradicate tumour [news release]. European Organisation for Research and Treatment of Cancer. Published October 1, 2020. Accessed October 20, 2020. https://www.eurekalert.org/pub_releases/2020-10/eofr-hbc092920.php