
Cancer is a disease characterized by the uncontrolled growth of abnormal cells. Nearly any type of cell in the body can become cancerous given the right circumstances, but some types of cancer are much more common than others.
In the United States, some of the most common types of cancer are female breast cancer, prostate cancer, lung cancer, colorectal cancer, and melanoma skin cancer. Nonmelanoma skin cancers (basal cell and squamous cell) are actually the most common type, but official numbers are not included in cancer registries.
Wherever they begin in the body, cancerous cells have multiple fundamental differences from normal cells. They grow and replicate at a much faster rate. They live much longer than normal cells, can evade the immune system, invade nearby tissues, and use up large amounts of resources.
Treatment for cancer
In the simplest and most basic terms, cancer treatment aims to eliminate cancer cells from the body. There are two main types of cancer treatments:
Localized therapies
These therapies are directed at a specific tumor or a cluster of cancerous cells in one area of the body. A well-known example is surgery to remove all or some of a tumor, as well as affected tissues and/or lymph nodes the cancer has spread to. Other examples of localized therapies include radiation therapy and ablation procedures, which destroy cancer cells with extreme heat or cold.
Systemic therapies
These are medications that travel through the bloodstream and act on cancer cells throughout the body. Chemotherapy is perhaps the most well-known example and is still a mainstay of treatment. Other systemic therapies include hormone therapy, immunotherapy, and targeted therapy.
Understanding your treatment options
If you or a loved one has been diagnosed with cancer, it’s important to understand your treatment options and how to discuss your treatment options with a healthcare team.
It’s common for a combination of therapies to be used to treat cancer. What therapies are recommended will depend on many different factors about the cancer, including the type, the location, the stage, and how the cancer is growing and how aggressively. An individual’s age, health, and personal preferences are also important considerations.
Questions when you are discussing a systemic therapy:
- What is the name of the medication and the dosage?
- Why is this medication recommended?
- How does the medication work?
- How is the medication administered?
- How often will this medication be administered?
- How long will I be taking this medication?
- What is the goal of this therapy? How will we know it is working? How will I be monitored during this part of treatment?
- What are the potential side effects? Is there a risk of serious side effects?
- How will I feel while taking this medication?
- Are there things I will need to avoid while taking this medication, such as certain foods or activities?
- Am I at risk for infections? Do I need to take precautions to avoid infections?
- Can this medication interact with other medications or supplements? Always tell your healthcare provider about all medications you are taking, including medications for other conditions, over-the-counter medications, and supplements.
- What will this therapy cost? Who can I talk to if I have concerns about the cost of treatment?
Questions when discussing surgery or another localized therapy:
- What is the name of the procedure?
- Why is this treatment recommended?
- What is removed during this procedure? Will I need reconstructive surgery?
- What is the goal of the procedure?
- What are the potential side effects or risks involved with this procedure?
- Do I need any tests or exams before this procedure?
- What healthcare provider will perform this procedure?
- Are there any alternatives to this approach to treatment?
- What will this procedure cost?
- What will the recovery process be like? How long will the recovery process take?
- Who can I talk to if I have concerns about the cost of treatment?
Remember, if you have questions about a diagnosis or treatment, need an explanation, or have concerns, your healthcare provider is your best source of information.
Sources: National Cancer Institute. What Is Cance... + 14
- National Cancer Institute. What Is Cancer? October 11, 2021.
- Cleveland Clinic. Cancer. August 19, 2024.
- National Cancer Institute. Common Cancer Types. May 6, 2025.
- American Cancer Society. Key Statistics for Basal and Squamous Cell Skin Cancers. October 31, 2023.
- NCI Dictionary of Cancer Terms. Localized therapy. Accessed May 6, 2026.
- National Cancer Institute. Surgery to Treat Cancer. November 8, 2024.
- Cynthia Demarco. How is ablation therapy used to treat cancer? MD Anderson Cancer Center. November 16, 2023.
- NCI Dictionary of Cancer Terms. Systemic therapy. Accessed May 6, 2026.
- Robert Peter Gale. Systemic Cancer Therapy. Merck Manual Professional Version. July 2024.
- Cleveland Clinic. Chemotherapy. October 20, 2022.
- Robert Peter Gale. Combination Cancer Therapy. Merck Manual Consumer Version. July 2024.
- American Cancer Society. Understanding Your Options for Cancer Treatment. July 24, 2025.
- National Cancer Institute. Questions to Ask Your Doctor about Treatment. February 22, 2023.
- MedlinePlus. Chemotherapy — what to ask your doctor. October 14, 2024.
- Johns Hopkins Medicine. Questions to Ask Before Surgery. Accessed May 6, 2026.



