Tucatinib in Patients With Locally Advanced or Metastatic HER2-positive Breast Cancer Who Received at Least Two Prior Anti-HER2 Treatment Regimens.

Only for prospectively enrolled patients: Time to deterioration of EORTC global health scale is defined as the time interval between fill-in date of baseline questionnaire and the first decrease in global health scale score ≥ 10-point (compared to baseline). If there was no such decrease, death will serve as event for this analysis, if occurring within 4 months after last filled-in questionnaire.

Only for prospectively enrolled patients: Changes in global health is provided by descriptive statistics of the EQ-5D-5L index value, the EQ-5D-5L visual analogue scale, the EORTC QLQ-C30 global health scale and all functional and symptom scores of the EORTC questionnaires.

TTNT (time to next systemic treatment) is defined as time from first administration of any study treatment (i.e., tucatinib/trastuzumab/capecitabine treatment) to start of a subsequent systemic antineoplastic therapy or death, whichever comes first.

TLT (time to local intracranial treatment) is defined as time from first administration of any study treatment to start of a local intracranial therapy, end of a treatment interruption due to isolated intracranial progression, change of treatment strategy or death, whichever comes first. It will be analyzed for patients with isolated intracranial progression after start of study treatment.

ORR is defined as proportion of patients with any response (partial or complete remission) overall.

DOR is defined as time from first occurrence of any response (complete or partial remission) to progression or death, whichever comes first. Analysis will be conducted in the subset of patients with any response.

CBR is defined as proportion of patients with complete or partial remission for best response or with stable disease lasting for at least 24 weeks.

Adverse events (AEs) and serious adverse events (SAEs) as characterized by type, frequency, severity and seriousness

During tucatinib administration, safety laboratory will be performed according to routine clinical practice. Laboratory values of AST (Aspartate aminotransferase) measured will be documented continuously during tucatinib treatment. Baseline levels of AST will be presented using descriptive statistics.

During tucatinib administration, safety laboratory will be performed according to routine clinical practice. Laboratory values of ALT (Alanine aminotransferase) measured will be documented continuously during tucatinib treatment. Baseline levels of ALT will be presented using descriptive statistics.

During tucatinib administration, safety laboratory will be performed according to routine clinical practice. Laboratory values of bilirubin measured will be documented continuously during tucatinib treatment. Baseline levels of bilirubin will be presented using descriptive statistics.

Frequencies and percentages of parameters affecting therapy choice.

Frequency/type of previous systemic antineoplastic treatments (neoadjuvant/adjuvant/palliative)

Frequency and type of previous anti-HER2 based regimens

Frequency and type of subsequent systemic antineoplastic therapies

Frequency and type of local antineoplastic therapies (surgeries, radiotherapies) incl. local intracranial therapies

Cohort 1: frequencies and percentages for line of treatment (1st-line or 2nd-line tucatinib treatment) Cohort 2: frequencies and percentages for line of treatment (3rd-line or 4th-line tucatinib treatment)

Treatment duration of study treatment in total and per substance

Dose intensity (absolute and relative) for each substance as prescribed by the treating physician

Frequency, type and reasons of dose modifications (dose reductions, skipped administrations/delays/interruption) compared to SmPC of tucatinib for each substance.

Frequency of usage of antidiarrheal drugs for prophylaxis and treatment of tucatinib-induced diarrhea