The EMILIA study found that trastuzumab emtansine (T-DM1) can improve progression-free survival in "some" women with metastatic breast cancer. The final arbiter of clinical approval is overall survival. Median overall survival for patients treated with T-DM1 was not reached. Drug response is not a reliable predictor of overall survival. Median progression-free survival was longer in patients treated with T-DM1 than in those treated with the standard therapy (9.6 vs 6.4 months). The difference reached is statistically significant?

The so-called immunoconjugates or antibody-drug conjugates (ADCs) are unique therapeutics that have become the focus of a plethora of recent and ongoing clinical trials, and for the first time since 2000 when Mylotarg (gemtuzumab ozogamicin) was approved in AML, the FDA gave the green light for another ADC, namely Adcetris (brentuximab vedotin) for the management of Hodgkins Lymphoma (HL) and systemic anaplastic large cell lymphoma (sALCL), like its sister agent in HER2-positive breast cancer, T-DM1, and other ADCs.

The ADCs do not work for all patients, T-DM1 is meant to treat only roughly 20 percent of breast cancer cases characterized by an abundance of that protein, and they are not totally free of side effects. And of course, T-DM1 is also likely to be very expensive, costing more than $100,000 for a typical course of treatment. One note: Mylotarg was removed from the market in 2010 after newer studies showed it did not prolong lives and had safety problems. At initial approval, Mylotarg was associated with a serious liver condition called veno-occlusive disease, which can be fatal.

T-DM1 is a "large molecule" and does not cross the blood-brain barrier (BBB). Some think that those on the T-DM1, they should also give the ladies some straight Herceptin, and give a certain amount of protection. The only way for that to happen is a patient may also have to be subjected to an "intrathecal" injection of T-DM1. Herceptin does not cross the BBB because it is a "large molecule" drug. Some on the trial developed brain metastases. Patients on T-DM1 will have to be on it "indefinitely" or until progression. Some on the trial developed brain metastases.

One thing you can definitely say is that T-DM1 is an investigational agent, or just plain experimental.