Breast cancer treatment is vastly different for a tumor that is positive for estrogen and progesterone and expresses HER2. Currently, for breast cancer tumors that express HER2, there are quite a few treatment options in IV and oral forms. However, IV forms increase the financial burden for the institution as well as for the patient. On February 28, 2019, the FDA approved the first-ever subcutaneous form in a combination of trastuzumab and hyaluronidase-oysk, for treating HER2 positive (HER2+) breast cancer. The approval was based on two large, randomized trials: HannaH and SafeHER.

HannaH was an open-label, multicenter, prospective, phase lll noninferiority trial that included 596 patients with HER2+ locally advanced breast cancer from October 19, 2009 to December 1, 2010. Patients received eight cycles of chemotherapy: four cycles of docetaxel followed by four cycles of fluorouracil, epirubicin, and cyclophosphamide with subcutaneous trastuzumab 600 mg or IV trastuzumab 8 mg/loading dose followed by 6 mg/kg every 3 weeks (neoadjuvant). After surgery, patients received 10 more cycles of subcutaneous (294 women) or IV trastuzumab (297 women).

Overall survival (84%), event-free survival (65%), and side effects were comparable in both groups. The results showed that safety and efficacy were comparable for the subcutaneous and IV forms. The subcutaneous route is an effective means of administration for patients with HER+ early breast cancer. This confirmed results of earlier trials, which showed similar complete-response rates.

SafeHER was a prospective, two-cohort, nonrandomized, multinational, open-label trial that looked at overall safety and tolerability of Herceptin Hylecta with chemotherapy in 1,864 patients with HER2-positive breast cancer. The drug was given with chemotherapy, after chemotherapy, or in combination with neoadjuvant chemotherapy. In this trial, side effects were more common when patients received Herceptin Hylecta concurrently with chemotherapy versus nonconcurrent chemotherapy. SafeHER confirmed the safety and tolerability of the fixed dose for 1 year.

With Herceptin Hylecta, cardiac monitoring should be performed with an ECHO or MUGA scan at baseline prior to initiation, every 3 months during administration, upon completion, and every 6 months for at least 2 years following completion of the drug. Herceptin Hylecta should be withheld if there is a ≥16% absolute decrease in left ventricular ejection fraction (LVEF) from pretreatment values or an LVEF value that is below institutional limits of normal and a ≥10% absolute decrease in LVEF from pretreatment values.

Herceptin Hylecta comes in individually packaged single-dose vials of 600 mg/10,000 units per 5 mL. It should be stored in the refrigerator at 2 degrees Celsius to 8 degrees Celsius in the original carton to protect it from light, and it should not be frozen or shaken. If it is taken out of the refrigerator, it must be administered within 4 hours.

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