This multicenter retrospective observational study investigates the incidence of malignant neoplasms in Parkinson's disease (PD) patients carrying heterozygous pathogenic variants in the GBA1 gene. The study compares these patients to individuals with idiopathic PD and to the general population within a large national cohort.

The rationale for the study lies in the growing evidence indicating an increased risk of malignant neoplasms in patients affected by Gaucher disease.

The primary objective is to assess whether PD patients with GBA1 mutations have a higher incidence of malignant neoplasms compared to the general population. Secondary objectives include comparing the incidence of malignant neoplasms between GBA1-PD and idiopathic PD patients, as well as between idiopathic PD patients and the general population. Additionally, the study aims to characterize oncological conditions by sex, age, center, and tumor site, with specific attention to distinguishing hematologic tumors from solid tumors.

By identifying potential associations between GBA1 mutations and malignancies in PD, the findings could guide more comprehensive patient management, including screening for malignant neoplasms alongside Parkinson's disease care.

The study will involve a network composed by different Italian Movement Disorders Centres and the corresponding local cancer registries, responsible for the active collection of cancer cases. Data will be collected from approximately 3000 consecutive Parkinson's disease (PD) patients, including about 500 patients carrying GBA1 mutations and 2500 idiopathic PD. Data about the presence of malignancies will be extracted from the Local Cancer Registries for each patient.

Inclusion Criteria:

• >18 years
• Diagnosis of Parkinson's Disease through the United Kingdom Parkinson's Disease Society Brain Bank Diagnostic Criteria for Parkinson's Disease.

Exclusion Criteria:

• Uncertain diagnosis

Participants will be selected from a network of Italian neurology centers with extensive experience in studying GBA-associated PD, in collaboration with local cancer registries. The study will include approximately 3,000 consecutive PD patients, subdivided into 500 patients with GBA mutations and 2,500 patients with idiopathic PD.

These participants will be compared with data from cancer registries to investigate potential associations between GBA mutations and malignancies. The population is drawn from specialized movement disorder centers and represents a clinically well-characterized cohort with access to standardized diagnostic and follow-up procedures.