Challenges of Differential Diagnosis Between Primary Hyperparathyroidism and Bone Metastases of Breast Cancer

Breast cancer might be complicated by distant metastases accompanied by hypercalcemia, but hyperparathyroidism is not commonly considered in the differential diagnosis. We present a case of 38 years old female patient who was diagnosed with ductal breast carcinoma. Eight months after the initial diagnosis the patient was diagnosed with distant bone metastases. However, this diagnosis was reconsidered at follow up, because we identified elevation of PTH 137.2 pg/ml, Ca²⁺ 1.19 mmol/l, albumin corrected calcium 2.42 mmol/l, 25(OH)D 39.4 nmol/l, indicating hyperparathyroidism. Scintigraphy with 99mTC-sestamibi confirmed parathyroid adenoma. Postoperative histopathology confirmed 1.2 g chief-cell PTA. Two months after the operation both PTH and Ca²⁺ levels were within the normal ranges. This study emphasizes the importance of considering possible hyperparathyroidism in patients with breast cancer and hypercalcemia. Routine evaluation of PTH is considered as a reasonable test in patients with breast cancer accompanied by bone lesions.

Abstract P2-13-17: A phase III, randomized, multicenter, double-blind study to compare efficacy and safety of EG12014 (EirGenix trastuzumab) with Herceptin® as neoadjuvant treatment in combination with anthracycline/paclitaxel-based systemic therapy in patients with HER2-positive early breast cancer - a multinational phase III study conducted during the COVID-19 pandemic

Amplification and/or overexpression of HER2 in breast cancer (BCa) patients is associated with aggressive disease and poor prognosis. Herceptin® (trastuzumab), a monoclonal antibody targeting HER2, has an established role in the treatment of HER2 positive BCa. Addition of trastuzumab to anthracycline- and taxane-based neoadjuvant treatment in women with HER2-positive BCa has resulted in improvements in pathological complete response (pCR, a strong predictor for long-term clinical outcome), event-free survival (EFS) and overall survival (OS). This study is designed to compare efficacy (pCR) and safety between the originator Herceptin and the proposed trastuzumab biosimilar EG12014. The study is conducted during the COVID-19 pandemic (last patient in: March 2020, last patient last visit: planned Jan 2022) in Belarus, Chile, Colombia, Georgia, India, Russia, South Africa, South Korea, Taiwan, and the Ukraine. Methods: Neoadjuvant phase: 807 patients were randomized (1:1) into 2 arms receiving epirubicin (90 mg/m2) and cyclophosphamide (600 mg/m2) every 3 weeks for 4 cycles, followed by EG12014 (arm 1) or Herceptin (arm 2) (both at loading dose: 8 mg/kg and maintenance dose: 6 mg/kg) and paclitaxel (175 mg/m2) every 3 weeks for 4 cycles. Subsequently, the patients underwent surgery, and primary endpoint (pCR [ypT0/is ypN0]) was assessed. Adjuvant phase: After surgery, the patients received EG12014 or Herceptin (both at loading dose: 8 mg/kg and maintenance dose: 6 mg/kg) to complete 12 months of overall trastuzumab treatment. COVID-19 infections in the study population were not expected to affect primary endpoint analysis; thus, no sensitivity analysis was performed regarding COVID-19 status (symptomatic/asymptomatic). Differences between the 2 arms regarding delays in study treatments and procedures due to COVID-19 were assessed. Results (at interim data base lock, blinded as study is ongoing): Study population: the mean age was 50 years, the majority were white Europeans with tumor stage II, estrogen receptor positive and progesterone receptor negative. The median time from date of first diagnosis was 0.5 months. Primary endpoint pCR (ypT0/is ypN0) was reached with relative risk ratio (RR) for the full analysis set: 0.992 (90% CI 0.880 to 1.118) between the 2 treatment arms. Secondary pCR endpoints (defined as ypT0 ypN0 and ypT0/is) were also reached, with RR between the treatment arms: 0.917 and 0.992, respectively. Objective clinical response prior to surgery was similar for the 2 treatment arms: 83.8% and 83.6%, respectively. EFS, OS, safety endpoints (e.g., adverse events [most frequently reported: alopecia], serious adverse events, and deaths), and toxicity assessments, supported similarity between EG12014 and Herceptin. Sixty-two patients (7.7%) were infected with COVID-19; the infections were equally distributed between the 2 treatment arms. COVID-19 did not cause any discontinuations or deaths in the study. Among all reported COVID-19 events, 13 (21%) were asymptomatic, 11 (18%) were graded as 3 (severe), and 1 (1.6%) was graded as grade 4 (life threatening). Conclusion: EG12014 has shown equivalent efficacy to Herceptin in regard to clinical response (pCR) and has also demonstrated a similar safety profile. The impact of the COVID-19 pandemic has been comparable between the two treatment arms. The influence of the pandemic on this clinical study has been relatively low considering timing and the participating countries. For further information, visit ClinicalTrials.gov (NCT03433313).

Citation Format: Barbara Grohmann-Izay, Chiun-Sheng Huang, Giorgi Dzagnidze, Nestor Llinas, Anand Misra, Denys Pominchuk, Alexander Prokhorov, Bernardo Rapoport, Vladimir Semiglazov, Ling-Ming Tseng, Eduardo Yanez Ruiz, Sibylle Loibl. A phase III, randomized, multicenter, double-blind study to compare efficacy and safety of EG12014 (EirGenix trastuzumab) with Herceptin® as neoadjuvant treatment in combination with anthracycline/paclitaxel-based systemic therapy in patients with HER2-positive early breast cancer - a multinational phase III study conducted during the COVID-19 pandemic [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-13-17.