Cancer is the leading cause of death in older dogs, and the welfare focus must balance treatment options against quality of life to avoid prolonging suffering.
Canine cancer creates significant welfare challenges at multiple decision points. Pain management for bone cancer is critical — untreated osteosarcoma causes severe, constant pain; palliative radiation can provide weeks of good quality life. Chemotherapy in dogs causes fewer severe side effects than in humans, but some protocols cause nausea and fatigue that must be weighed against benefit. The most important welfare principle is honest quality-of-life assessment: treatment that extends life while significantly reducing its quality serves owner psychological needs more than dog welfare. Validated quality-of-life scales (HHHHHMM scale, Villalobos) provide structured frameworks for these difficult decisions.