Final answer:
The lethal aspect of cancer is primarily due to metastasis, where cancer cells spread to other parts of the body, disrupting the function of vital organs. Treatment focuses on halting uncontrolled cell division and correcting programmed cell death mechanisms.
Step-by-step explanation:
The aspect of cancer that ultimately can lead to death is mainly due to metastasis and the invasion of surrounding tissues. Cancerous cells accumulate DNA mutations and proliferate uncontrollably, forming tumors. While a benign tumor is typically localized, malignant tumors have the potential to spread through the body. Metastasis occurs when cancer cells break away from the original tumor and travel through the blood or lymph system to form new tumors in other parts of the body. This ability to spread is a defining characteristic of cancer and can severely impair the function of essential organs, leading to life-threatening complications. Cancer treatment aims to prevent this progression and can include targeting the mechanisms of uncontrolled cell division and influencing apoptosis, the process of programmed cell death which is often disrupted in cancer cells.