Objective To evaluate the change in adjuvant therapeutic decision in a cohort of young women with breast cancer discussed by a multidisciplinary team, before and after EndoPredict testing. Patients and methods 99 premenopausal women with hormone receptor-positive, HER2-negative, T1-T2, and N0-N1 breast cancer were included. Clinicopathological characteristics were recorded and cases were presented in a multidisciplinary tumor board. Consensual therapeutic decisions before and after EndoPredict results were registered. Medical records were reviewed at six-month follow-up to determine physicians' adherence to therapeutic recommendations. Pearson chi-square and McNemar's tests were used to analyze differences between groups and changes in treatment recommendations, respectively. Results Median age at diagnosis was 43 years. The most frequent tumor size was pT2 (53.5%) and 27% of patients had 1-3 positive lymph nodes. 46% of patients had a low-risk EPclin result. Nodal status and tumor grade were significantly associated with EPclin result (p < .00001 and p = .0110, respectively), while Ki67 levels and age �40 years were not. A change in chemotherapy decision was registered in 19.2% of patients (p = .066), with the greatest impact in de-escalation (9% net reduction). A change in chemotherapy or endocrine therapy regimen was suggested in 19% and 20% of cases, respectively, after EPclin results were available. A significant difference was found in the median EPclin score between patients with a low-vs. high-intensity chemotherapy and endocrine therapy regimen

Molecular subtype discordance in bilateral synchronous breast cancer is a relatively uncommon entity that poses unique therapeutic challenges. Here we report the case of a 35-year-old woman who presented to our clinic with synchronous bilateral breast cancer (SBBC), with stage IIA triple-negative disease in the right breast and a stage IIB hormone-sensitive tumor in the left breast. She was treated with bilateral modified radical mastectomy and axillary node dissection followed by adjuvant chemotherapy, radiotherapy, and a five-year regimen with daily tamoxifen. To date, the patient remains asymptomatic and free of disease recurrence 78 months after initiating treatment. Little is known about SBBC with a discordant molecular subtype and reports about this entity are scarce. Future studies aimed at identifying the optimal management strategy for this disease are needed.

e18387 Background: The subcutaneous presentation of trastuzumab has been recently incorporated into the treatment regimen of HER2-positive breast cancer (BC). Its use has been associated with cost savings and reduced chair time, being especially suitable for public health systems. Aim: To estimate the cost savings of the use of SC-T compared to intravenous trastuzumab (IV-T) according to patient weight, and calculate the infusion time of SC-T in a tertiary healthcare facility at TecSalud from Feb 2018 - Jan 2019. Methods: From a total of 2068 oncological treatments, 756 corresponded to SC-T, either alone or concomitantly with chemotherapy (CT). For cost estimation, we considered $1,103 USD per SC-T vial, $1,162 USD per IV-T vial and $2.6 USD per mg of IV-T, as per governmental rates. We compared the actual treatment cost of 600 mg fixed SC-T dose with the hypothetical cost of administering IV-T at a dose of 6 mg/kg, considering its price per vial and per mg. The total time of SC-T infusion was reported. Results: Median patient weight for the 756 reported SC-T treatments was 72 kg (45 - 127 kg). Of these, 561 consisted of SC-T alone; and 56% had adjuvant, 34% neoadjuvant and 10% palliative intent. The estimated cost of the 756 doses of SC-T was $833,500 USD. Considering patients’ weight, 46% of the infusion treatments would have required 2 IV-T vials, with a total of 1105 vials and an absolute cost of $1,282,374 USD. Likewise, if cost per mg of IV-T is examined, we would have used 338,744 mg of IV-T, with an estimated cost of $894,284 USD. Approximate savings of SC-T use would reach $448,874 USD per vial payment and $60,784 USD per mg payment. The median time of SC-T only infusion was of 3 minutes (1 - 20 minutes); and no adverse effects were documented during its administration. Conclusions: The SC-T fixed dose (irrespectively of patients’ weight) results in significant practical and financial advantages as weight-adjusted dosing is not required. This is specially relevant in countries like Mexico, where > 70% of BC patients are overweight/obese, requiring higher doses of IV-T and resulting in greater expenses. Thus, the use of SC-T not only offers greater convenience to patients, but also reduces overall healthcare costs compared to standard IV infusion.