The primary objective is:

• To determine the efficacy of modafinil in the reduction of fatigue in patients with metastatic breast or prostate cancer undergoing docetaxel-based chemotherapy

The secondary objectives are:

• To determine the effect of modafinil on quality of life (QoL) during docetaxel-based chemotherapy
• To determine the effect of modafinil on patients physical activity level, functional status, number of chemotherapy cycles tolerated, sleep disturbance and depression, during docetaxel-based chemotherapy
• To investigate the impact of tumour type, patient physical activity level, functional status, sleep disturbance and depression on the efficacy of modafinil at improving fatigue and quality of life during docetaxel-based chemotherapy.
• To determine the safety and tolerability of modafinil during docetaxel-based chemotherapy

Inclusion criteria:

• Treatment with q3w (every three weeks) docetaxel-based chemotherapy for metastatic breast or prostate cancer at a minimum dose of 50 mg/m2
• Completed at least two cycles of chemotherapy and intention to treat the patient with at least two further cycles of docetaxel-based chemotherapy
• Fatigue > or = to 4 on the MD Anderson Symptom Inventory fatigue assessment scale during the previous docetaxel chemotherapy cycle
• SPHERE somatic (SOMA) subscale score > or = to 3
• Worsening of fatigue after commencement of docetaxel chemotherapy
• Haemoglobin (Hb)> or = to 10 g/dL within two weeks before randomisation

Exclusion criteria:

• Unable to complete the MD Anderson Symptom Inventory fatigue assessment scale or Functional Assessment of Chronic Illness Therapy-Fatigue Quality of Life survey
• Require docetaxel chemotherapy dose reduction to less than 50 mg/m2
• History of chronic fatigue condition
• Uncontrolled hypertension (blood pressure > or = to 150/90 mm Hg
• Known hypersensitivity / intolerance to modafinil or any of the excipients
• Pregnant women
• Psychological, familial, sociological, or geographical conditions that do not permit treatment or medical follow-up and / or prohibit compliance with the study protocol
• Any serious concomitant illness that, in the opinion of the Investigator, would preclude a patient from participating in the study
• Non-English speaking

The above information is not intended to contain all considerations relevant to a patient's potential participation in a clinical trial.