The study will provide information on outcomes in people with multiple myeloma, or systemic AL amyloidosis, or both, under standard care. AL is short for amyloid light-chain. Standard care means the participant will be treated according to their clinic's standard practice. The study sponsor will not be involved in how participants are treated but will provide instructions on how the clinics will record what happens during the study.

The aim of the study is to learn if treatment duration makes a difference in how participants with multiple myeloma or systemic AL amyloidosis respond to their treatment.

During the study, participants will be treated according to their clinic's standard practice. Participants must have started their treatment up to 12 months before taking part in this study. During the study, the participants will visit their clinic every 3 months. These are extra visits to their clinic's standard visits.

This is a prospective non-interventional study to assess the DoT and response in participants with MM or systemic AL amyloidosis in standard clinical practice.

This study will enroll approximately 250 participants (220 with MM and 30 with systemic AL amyloidosis). Participants will be enrolled in 2 groups:

Participants with MM Participants with AL amyloidosis The study will have a prospective data collection of the participants from clinical records and scheduled visits following the routine clinical practice. All participants will receive treatment at study start and this treatment must have been started within 12 months before the participant's enrollment.

This multi-center study will be conducted in Spain. Participants will be followed until 12 months after enrollment. The overall time to participate in this study is approximately 1 year.

Inclusion Criteria:

1. Diagnosis of MM and/or AL amyloidosis according to the IMWG for MM and BSH guidelines for AL amyloidosis.

   MM diagnostic criteria:

   • Smouldering MM- Both criteria must be met:

     1. Serum M protein (Immunoglobulin G [IgG] or IgA greater than or equal to (>=) 30 gram per liter (g/L) or urinary monoclonal protein (M protein) >= 500 milligram per 24 hours (mg/24 h) and/or clonal bone marrow (BM) plasma cells (PCs) 1 percent (%) - 60%.
     2. Absence of myeloma-defining events or amyloidosis.

   • Multiple myeloma- Clonal BM plasma cells >= 10% or biopsy-proven bony or extramedullary plasmacytoma and any one or more of the following myeloma-defining events:

     1. Evidence of end organ damage that can be attributed to the underlying plasma cell proliferative disorder, specifically:

        • Hypercalcemia: serum calcium greater than (>) 0.25 millimole per liter (mmol/L) (> 1 milligram per deciliter [mg/dL]) higher than the upper limit of normal or >2.75 mmol/L (>11 mg/dL).
        • Renal insufficiency: creatinine clearance (CrCl) less than (<) 40 milliliter per minute (mL/min) or serum creatinine >177 micromole/liter (mcmol/L) (>2 mg/dL).
        • Anemia: haemoglobin (Hb) value of >20 g/L below the lower limit of normal or a Hb value of <100 g/L.
        • Bone lesions: one or more osteolytic lesions on skeletal radiography, computed tomography (CT) or positron emission tomography-computed tomography (PET-CT).

     2. Any one or more of the following biomarkers of malignancy:

        • >=60% clonal BM plasma cells.
        • Involved/uninvolved serum-free light chain ratio >=100.
        • >1 focal lesions on magnetic resonance imaging (MRI) studies (each focal lesion must be >=5 millimeter (mm) in size).

   AL amyloidosis diagnosis:

   • In suspected AL amyloidosis, a histological diagnosis is essential and, where possible, a biopsy should be taken from an apparently affected organ. Alternatively, a subcutaneous abdominal fat aspirate and bone marrow biopsy may be examined for amyloid.
   • Congo red staining with classical apple green birefringence under polarized light should be used to test for the presence of amyloid on any histological specimen.
   • The diagnosis of amyloid requires an experienced laboratory as false negative and false positive diagnoses on the basis of histology are not infrequent. Other (non-AL) amyloid fibril types should be excluded by using immunohistochemistry, deoxyribonucleic acid (DNA) analysis, protein sequencing or mass spectrometry.

2. Under treatment for MM or systemic AL amyloidosis at the time of study entry.

3. Have started treatment up to 12 months before inclusion for MM or systemic AL amyloidosis, irrespective of the treatment regimen.

4. Having first, second, third or fourth line of treatment for MM or systemic AL amyloidosis, irrespective of the treatment regimen.

5. In case of participants with Newly Diagnosed Multiple Myeloma (NDMM) who are candidates to autologous stem cell transplant (ASCT), the ASCT has to be performed before study entry.

Exclusion Criteria:

1. Participants with planned cessation of treatment for MM or systemic AL amyloidosis from participation to the study (example, due to pregnancy).
2. Participating in blinded clinical trials, or in clinical trials with no possibility of obtaining information required in this study, or in clinical trials in which participation in other studies is not allowed.

Participants diagnosed with MM or systemic AL amyloidosis.

Takeda provides access to the de-identified individual participant data (IPD) for eligible studies to aid qualified researchers in addressing legitimate scientific objectives (Takeda's data sharing commitment is available on https://clinicaltrials.takeda.com/takedas-commitment?commitment=5). These IPDs will be provided in a secure research environment following approval of a data sharing request, and under the terms of a data sharing agreement.

IPD from eligible studies will be shared with qualified researchers according to the criteria and process described on https://vivli.org/ourmember/takeda/. For approved requests, the researchers will be provided access to anonymized data (to respect patient privacy in line with applicable laws and regulations) and with information necessary to address the research objectives under the terms of a data sharing agreement.