Trastuzumab Biosimilar (Samfenet®) Plus Treatment of Physician's Choice (TPC) in Patients With HER2-positive Solid Tumor

Inclusion Criteria: * Histologically or cytologically confirmed HER2 -overexpression (HER2 overexpression defined as 3+ positive by immunohistochemistry, positive by fluorescence in situ hybridization (FISH), or confirmation of HER2 amplification). However hepatic cancer and breast cancer are exclude as HER2 targeted treatment is already a standard treatment for these tumor types. * Patients who have progressed after at least one standard treatment or unable to continue standard treatment due to adverse events. * Patients confirmed as metastatic or unresectable cancer by imaging test * At least one measurable lesion that can be accurately assessed by imaging according to RECIST v1.1 * Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2 at trial entry * Adequate organ function (bone marrow, liver, kidney function) A. ANC ≥ 1000/mL B.Platelets ≥ 75,000/uL C.Hemoglobin \>8.0 g/dL D.Total bilirubin ≤ 2.0x ULN E.AST and ALT \< 5.0 x ULN F.Alkaline phosphatase \<2.5x ULN GCreatinine ≤ 2.0x ULN or CCr \>30 ml/min * Estimated life expectancy of more than 3 months * Left ventricular ejection fraction of at least ≥ 50% at trial entry * Age ≥19 years who have signed an informed consent approved by Institutional Review Board of Organization Exclusion Criteria: * Either woman of pregnancy or breast-feeding woman who is positive for hCG * Symptomatic or unstable metastases to central nervous system (exceptions : properly treated brain metastasis with no evidence of progression on CT or MRI scan compared with prior examination and without requirement for steroid therapy for relief of symptom. Treatment of an anticonvulsant of stable dose for more than 4 months is permitted taken. * Evidence of viral, bacterial, or fungal infection including active hepatitis C and D or HIV infection. * Underwent major surgery of have not fully recovered from certain procedures within 4 months prior to taking the investigational product * History of malignant disease within 3 years prior to taking the investigational product (exceptions: treated carcinoma in situ of cervix, differentiated thyroid cancer without lymph node metastasis, and skin cancer other than melanoma). * Interval of QTc \> 480 msec (in terms of average measurement of EKG 3 times), oneself or family known to be long or short QT, brugada syndrome or other known QTc prolongation history or Torsade de Pointes. * Following symptoms or disease within 6 months prior to taking the investigational product: myocardiac infarction, NCI CTCAE v 5.0 Grade ≤2 severe/unstable angina, continuous arrhythmia, atrial fibrillation, bypass surgery of coronary or peripheral arteries, symptomatic heart failure, cerebrovascular events including transient ischemic attack, or symptomatic pulmonary embolism. * History of symptomatic interstitial lung disease * Hypersensitivity reaction to Trastuzumab, Gemcitabine, Irinotecan or components of these agents * Patients with diarrhea, intestinal paralysis, intestinal obstruction, massive ascites, or pleural effusion * Other psychiatric problems, suicidal attempt, abnormal test results that can affect the administration of the investigational product or participation of clinical trial or that can impact the results of the clinical trial, and any other reason that investigator acknowledge as unsuitable factor for participating the clinical trial.