Stumbling around/ staggering across at his lawn; Felt dizzy; Tiredness; This spontaneous case was received on 03-Jan-2023 from other healthcare professional via Med Communications (reference number: SEQW23-00030) and concerned a 66-year-old, male patient. The patient was enrolled in an Astellas sponsored patient support program (enzalutamide_Astellas PSP).  The patient's concurrent conditions included secondary malignant neoplasm of bone and prostate cancer. The patient's historical conditions included other specified diseases of the liver. The patient's concomitant medications included Lupron (leuprorelin acetate), Metamucil sugar free (Plantago ovata), and Zometa (zoledronic acid), all used for unreported indications, and Xtandi (enzalutamide) used for prostate cancer. The patient had no known allergies.  On 22-Oct-2022, Saturday, the patient was vaccinated with Flucelvax Quadrivalent (influenza vaccine inact sag 4v; dose: 0.5 ml, route of administration and anatomical location: not reported) for active immunization for the prevention of influenza disease caused by influenza virus subtypes A and B contained in the vaccine. The batch number was not reported.  On the same date, the patient was vaccinated with non-company, co-suspect Pfizer BioNTech COVID-19 vaccine (tozinameran; dose: reported as 'fourth, booster', route of administration, anatomical location, and indication: not reported). The batch number was not reported.  On 27-Oct-2022, five days after receiving Flucelvax Quadrivalent and co-suspect Pfizer BioNTech COVID-19 vaccine, and about 30 minutes after morning dose of Xtandi (enzalutamide), the patient was stumbling around/staggering across at his lawn, felt dizzy and the patient experienced tiredness.  It was reported that the patient did not take blood pressure medications just leuprorelin acetate and zoledronic acid. The patient might switch routine in taking it (enzalutamide) and would try eating before rather than after (as reported). The patient was encouraged to reach out to the doctor since dizziness was preventing him from working.  On 28-Oct-2022, the dose of Xtandi (enzalutamide) was changed from 160 mg daily to 120 mg daily.  On an unspecified day, the patient recovered from the events of 'gait disturbance' and dizzy.  At the time of initial reporting, the patient had not recovered from the event of tiredness.  The reporter did not provide causality assessment.   The case was assessed as non-serious.  Company comment: A 66-year-old male patient experienced dizziness, gait disturbance and fatigue five days after vaccination with Flucelvax Quadrivalent and co-suspect Pfizer BioNTech COVID-19 vaccine, and about 30 minutes after morning dose of Xtandi (enzalutamide). The patient's concurrent conditions included secondary malignant neoplasm of bone and prostate cancer. The patient was on treatment with Xtandi (enzalutamide) used for prostate cancer. Reportedly, the patient might switch routine in taking enzalutamide. The dose of enzalutamide was reduced. Common side effects of Xtandi (enzalutamide) included fatigue and dizziness, which is probable cause for all events due to suggestive temporal relationship. Therefore, causality for all events is assessed as not related to the suspect vaccine due to alternative aetiology provided. Sender's Comments: A 66-year-old male patient experienced dizziness, gait disturbance and fatigue five days after vaccination with Flucelvax Quadrivalent and co-suspect Pfizer BioNTech COVID-19 vaccine, and about 30 minutes after morning dose of Xtandi (enzalutamide). The patient's concurrent conditions included secondary malignant neoplasm of bone and prostate cancer. The patient was on treatment with Xtandi (enzalutamide) used for prostate cancer. Reportedly, the patient might switch routine in taking enzalutamide. The dose of enzalutamide was reduced. Common side effects of Xtandi (enzalutamide) included fatigue and dizziness, which is probable cause for all events due to suggestive temporal relationship. Therefore, causality for all events is assessed as not related to the suspect vaccine due to alternative aetiology provided.