Treatment outcomes of tucatinib in combination with trastuzumab and pertuzumab as a maintenance therapy for people with HER2+ metastatic breast cancer: a plain language summary of findings from HER2CLIMB-05

Plain Language SummaryWhat is this summary about?This summary describes an article published in the Journal of Clinical Oncology in December 2025. The article reports the results of a clinical trial called HER2CLIMB-05, which evaluated how well the addition of tucatinib to standard maintenance therapy (trastuzumab and pertuzumab) stops cancer from getting worse in people with human epidermal growth factor receptor 2-positive (HER2+) metastatic breast cancer.This study included people with HER2+ metastatic breast cancer whose cancer did not get worse after 4 to 8 treatments of first-line chemotherapy combined with trastuzumab and pertuzumab. These individuals were then randomly assigned to receive either tucatinib or placebo in combination with standard maintenance therapy. To evaluate how well the treatments worked, individuals were monitored for cancer worsening by measuring tumor sites on a regular basis. Overall, the researchers wanted to know how long individuals lived without their cancer getting worse and what side effects could happen when receiving the tucatinib combination.What were the results?The HER2CLIMB-05 study showed that people with HER2+ metastatic breast cancer treated with tucatinib plus standard maintenance therapy lived longer without their cancer worsening than people treated with placebo plus standard maintenance therapy. The length of time people lived without their cancer worsening was 24.9 months among those who received the tucatinib combination, and 16.3 months among those who received the placebo combination.The most frequently reported side effects that occurred among the people receiving the tucatinib combination included diarrhea (73%), nausea (33%), elevated levels of liver enzymes (26%–28%), joint pain (21%), and fatigue (21%). These side effects were mostly manageable with supportive care (e.g., taking an anti-diarrhea medication) and/or lowering or holding the dose of the treatment.What do the results mean?The results of the HER2CLIMB-05 study suggest that adding tucatinib to standard maintenance therapy significantly prolongs the length of time that people with HER2+ metastatic breast cancer live without their cancer worsening following first-line therapy with chemotherapy and trastuzumab and pertuzumab.Clinical trial number: NCT05132582