This is a large randomized, double-blind, placebo-controlled trial to determine the efficacy of testosterone replacement on cancer-related fatigue in older men with solid or hematologic (blood) cancer who report fatigue and have low testosterone levels.

The overall objective is to conduct a double-blind, randomized, placebo-controlled, parallel group trial to determine the efficacy of 6 months of physiological testosterone replacement therapy in improving cancer related fatigue, sexual dysfunction, and body composition and muscle function in men 55 years and older with solid or hematologic (blood) cancers, who report fatigue and have testosterone deficiency. There will be 5 study visits: 1) Screening, 2) Baseline, 3) 2-Week Dose Adjustment Visit, 4) Three-month visit (Week 12), and 5) Six-month visit. Testosterone or placebo gels will be applied by eligible trial participants at home; participants will be trained on gel application procedures by research personnel.

Inclusion Criteria:

• Men with active solid or hematologic (blood) cancers who have received or are receiving chemo- and/or radiation therapy. Patients who have no evidence of disease (NED) for 60 months or less, which means that they are <60 months from their last treatment (chemotherapy and/or radiation therapy) will be included.
• Age: 55 years and older
• Life expectancy of at least 6 months.
• Serum testosterone, measured by mass spectrometry (gold standard method), of <348 ng/dl and/or free testosterone <70 pg/ml. The lower limits of the normal range for total testosterone in healthy men is 348 ng/dL and the lower limits of free testosterone is <70 pg/ml in the Framingham Heart Study sample. As sex hormone binding globulin levels may be elevated in some men with cancer (resulting in elevation in total testosterone level), some of these symptomatic men may still be hypogonadal despite having total testosterone above this cut-off limit, but their free testosterone levels may still be below the lower limit of normal. Thus, men with free testosterone <70 pg/mL will be included.
• Fatigue. Fatigue was selected as it is a highly prevalent symptom in cancer patients. Fatigue will be defined as a score on FACIT-Fatigue subscale of <40, which best divides cancer patients from the general population with accuracy.
• Ability and willingness to provide informed consent

Exclusion Criteria:

• Men with current or prior history of prostate, breast, testicular, or adrenal cancers.
• Use of anabolic agents (testosterone, DHEA, growth hormone) within the past 6 months
• Hematocrit >48%, serum creatinine >2.5 mg/dL
• PSA >4 ng/ml; nodule or induration on digital rectal exam
• Severe untreated sleep apnea
• Uncontrolled congestive heart failure
• Myocardial infarction, acute coronary syndrome, revascularization surgery, stroke or thromboembolism (of any etiology) within 6 months
• Known history of thrombophilia due to a genetic mutation (e.g. Factor V Leiden)
• Previous stroke with residual cognitive or functional deficits
• Inability to provide informed consent; MMSE score <24
• Poorly controlled diabetes as defined by hemoglobin A1c >10.0%
• Body mass index (BMI) >40 kg/m2
• Bipolar disorder or schizophrenia