EMILIA: What the Breast Cancer Trial Found

The idea EMILIA was testing

An antibody-drug conjugate is a targeted antibody with a chemotherapy drug bolted onto it. The antibody finds the cancer cell. The chemotherapy is meant to be released mostly there, rather than everywhere. T-DM1, or trastuzumab emtansine, pairs the HER2 antibody trastuzumab with a cell-killing drug called DM1.

By 2012 that idea was promising but unproven in a large trial. EMILIA tested it.

The comparison, and who was in it

991 people with HER2-positive advanced breast cancer took part. All had already been treated with trastuzumab and a taxane chemotherapy. They were assigned to T-DM1 or to lapatinib plus capecitabine, which was then a normal second-line choice.

Both clocks moved

Independent reviewers, not the treating doctors, judged when the cancer grew. By that measure the median was 9.6 months with T-DM1 and 6.4 months with lapatinib plus capecitabine. The hazard ratio was 0.65 (95% CI 0.55 to 0.77; P<0.001), or about a 35% lower risk of the cancer growing or the person dying at any moment.

Survival moved as well: a median of 30.9 months against 25.1 months, hazard ratio 0.68 (95% CI 0.55 to 0.85; P<0.001). The gap was clear enough that it crossed the trial's stopping rule at the second interim look. Tumors shrank in 43.6% of the T-DM1 group and 30.8% of the comparison group (P<0.001).

Fewer severe side effects, but a different set

Grade 3 or 4 side effects were less common with T-DM1: 41% against 57%. That combination — better results and less harm — is rare in cancer trials, and it is the main reason EMILIA is remembered.

The trade was in the type of harm rather than the amount. Low platelet counts and raised liver enzymes were more frequent with T-DM1. Diarrhea, nausea, vomiting and painful hands and feet were more frequent with lapatinib plus capecitabine.

Where EMILIA sits now

T-DM1 became the standard second treatment for HER2-positive advanced breast cancer for close to a decade. It also proved the antibody-drug conjugate design worked, which opened the door to the drugs that followed. One of those, trastuzumab deruxtecan, later beat T-DM1 directly in DESTINY-Breast03. T-DM1 is no longer the usual second choice.

What this trial cannot tell you today

• Its comparison arm, lapatinib plus capecitabine, is rarely used now. That makes the size of the advantage hard to translate to a current decision.
• Everyone had already had trastuzumab and a taxane, so it says nothing about first treatment.
• It predates the newer HER2 drugs entirely and cannot rank T-DM1 against them.
• Median figures describe the middle of a group. Individual results ranged widely on both arms.

If you are weighing a HER2 treatment

• Where does this drug sit in the order of treatments for me now?
• Which HER2 drugs have I already had, and does that rule any out?
• What blood tests would be checked before each dose, and why?
• Is a newer antibody-drug conjugate an option in my situation?

Sources

This article was written from the sources below, which were checked on the source-check date shown above.

• NEJM: Trastuzumab Emtansine for HER2-Positive Advanced Breast Cancer (EMILIA) (primary)

How this article was prepared

Prepared by Cancer Explained's AI-assisted editorial system and checked against the sources listed below. This article has not been reviewed by a healthcare professional unless a named reviewer is specifically shown.

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