This study is looking at how testosterone replacement can help with tiredness, sexual problems, and overall well-being in older men (55+) with cancer and low testosterone levels. The study is **randomized** (participants are chosen at random), **double-blind** (neither participants nor doctors know who receives the treatment), and **placebo-controlled** (some participants get fake treatment). It lasts for 6 months with 5 visits: Screening, Baseline, 2-week check, 3-month, and 6-month visits. Participants will use gel treatments at home and be trained by the study team. To join, you need to have certain types of cancer, be 55 or older, and have low testosterone. You can't participate if you have prostate or breast cancer, or other serious health problems.

• **Study Length**: 6 months with 5 visits
• **Treatment**: Use gel at home
• **Eligibility**: Men 55+, specific cancer types, low testosterone