Cancer Treatment: Surgery, Chemotherapy, Radiation, and More

What are the main categories of cancer treatment?

(Surgery, Chemotherapy, Radiation, Targeted Therapy, Immunotherapy, Hormone Therapy, Stem Cell Transplant, others like ablation)

·  Surgery: Physically removing the tumor and surrounding tissue.

·  Chemotherapy: Using drugs to kill cancer cells throughout the body.

·  Radiation Therapy: Using high-energy rays to target and destroy cancer cells in a specific area.

·  Targeted Therapy: Using drugs that target specific molecules within cancer cells to stop their growth and spread.

·  Immunotherapy: Helping the body’s own immune system fight cancer.

·  Hormone Therapy: Blocking or removing hormones that fuel the growth of certain cancers.

·  Stem Cell Transplant: Replacing damaged blood-forming cells with healthy ones. This is often used after high-dose chemotherapy or radiation therapy.

·  Ablation: A minimally invasive procedure that uses extreme heat or cold to destroy cancer cells. Different types of ablation include:

• Radiofrequency ablation: Uses electrical energy to heat and kill cancer cells.
• Cryoablation: Uses extreme cold to freeze and destroy cancer cells.
• Microwave ablation: Uses electromagnetic waves to heat and kill cancer cells.
• Laser ablation: Uses focused laser beams to destroy cancer cells.

When is surgery typically used in cancer treatment?

(For solid tumors, diagnosis, staging, removal, symptom relief)

Surgery is a versatile tool in cancer treatment and is typically used in several key situations:

• For Solid Tumors: Surgery is a primary treatment for many solid tumors that are localized (confined to one area). The goal is often to completely remove the tumor and any nearby cancerous tissue. This is most effective when the cancer has not spread to distant parts of the body (metastasized).
• Diagnosis: Surgical procedures, such as biopsies (taking a small tissue sample), are crucial for diagnosis. Pathologists examine the tissue under a microscope to determine if cancer is present, the type of cancer, and its grade (how aggressive it looks).
• Staging: Surgery can be part of the staging process. Staging helps determine the extent of the cancer, including the size of the tumor, whether it has spread to nearby lymph nodes, and if it has metastasized to other organs. Surgical exploration and removal of lymph nodes are common staging procedures for many cancers.
• Removal (Curative Resection): This is often the primary goal of surgery. If the cancer is localized and can be completely removed with clear margins (no cancer cells seen at the edge of the removed tissue), surgery can be curative.
• Symptom Relief (Palliative Surgery): Even when a cancer cannot be cured, surgery can sometimes be used for symptom relief. This is called palliative surgery. Examples include:
  • Removing a tumor that is causing pain, obstruction, or bleeding.
  • Creating a bypass to relieve a blockage in the digestive system.
  • Inserting a feeding tube if a tumor is preventing normal eating.

How does chemotherapy work?

(Uses drugs to kill rapidly dividing cells, including cancer cells)

•  Targeting Rapid Cell Division: Chemotherapy drugs are designed to interfere with the process of cell division (mitosis). They can damage the DNA or RNA of cells, or disrupt the proteins necessary for cell division. Because cancer cells are in a state of constant and rapid division, they are more susceptible to these drugs than most healthy cells, which divide at a slower rate or not at all.  
• Systemic Treatment: Most chemotherapy drugs are administered orally or intravenously, allowing them to travel throughout the bloodstream and reach cancer cells almost anywhere in the body. This makes chemotherapy particularly useful for cancers that have spread (metastasized) beyond the original tumor site.  
• Cell Cycle Specificity: Some chemotherapy drugs are most effective during specific phases of the cell cycle (the series of events a cell goes through as it grows and divides), while others can act on cells in any phase. Often, combinations of drugs with different mechanisms of action and cell cycle specificities are used to maximize the killing of cancer cells.  
• Damage to Healthy Cells: While chemotherapy primarily targets rapidly dividing cells, it can also affect healthy cells that divide quickly, such as those in the hair follicles, bone marrow, and lining of the mouth and intestines. This damage to normal cells is what causes many of the common side effects of chemotherapy.  

What are the different ways radiation therapy can be delivered? (External beam, internal/brachytherapy)

Radiation therapy can be delivered in several different ways, broadly categorized into:

1. External Beam Radiation Therapy (EBRT):

• This is the most common type of radiation therapy.  
• A machine outside the body directs high-energy beams (like X-rays, gamma rays, electron beams, or proton beams) at the tumor.  
• The machine does not touch the patient.  
• Treatment is usually given in daily fractions (small doses) over several weeks.  
• Different techniques within EBRT allow for more precise targeting of the tumor and minimization of damage to surrounding healthy tissues. These include:
  • 3D-Conformal Radiation Therapy (3D-CRT): Uses CT, MRI, or PET scans to create a 3D image of the tumor, shaping the radiation beams to match its contours.  
  • Intensity-Modulated Radiation Therapy (IMRT): Similar to 3D-CRT but can also adjust the intensity of the radiation beams from different angles to deliver varying doses within the tumor and further spare healthy tissue.  
  • Image-Guided Radiation Therapy (IGRT): Uses imaging scans (like CT or X-rays) before and sometimes during treatment to ensure accurate positioning of the patient and targeting of the tumor, accounting for any movement.  
  • Stereotactic Radiosurgery (SRS) and Stereotactic Body Radiation Therapy (SBRT/SABR): Deliver very high doses of precisely focused radiation in one or a few sessions to small tumors in the brain (SRS) or other parts of the body (SBRT/SABR).  
  • Proton Beam Therapy: Uses protons instead of photons (X-rays) to deliver radiation. Protons deposit most of their energy at a specific depth, potentially reducing damage to tissues beyond the tumor.  
  • Intraoperative Radiation Therapy (IORT): Radiation is delivered directly to the tumor bed during surgery after the tumor has been removed. This allows for a high dose of radiation to the area with the highest risk of recurrence while sparing surrounding healthy tissues.  

2. Internal Radiation Therapy (Brachytherapy):

• This involves placing a radioactive source directly inside the body, in or near the tumor.  
• This allows for a high dose of radiation to be delivered to a small area while limiting exposure to surrounding healthy tissues.  
• The radioactive source can be in the form of seeds, ribbons, wires, needles, capsules, or applicators.  
• Brachytherapy can be:
  • Temporary: The radioactive source is placed in the body for a specific time (from minutes to days) and then removed. This can be delivered at:
    • High-Dose Rate (HDR): A strong radioactive source is placed for a short period.  
    • Low-Dose Rate (LDR): A weaker radioactive source is left in place for a longer duration.
  • Permanent (Seed Implantation): Small radioactive seeds are implanted directly into the tumor and left there. They release radiation over time and eventually become inactive.

What is the difference between targeted therapy and chemotherapy?

(Targeted therapy attacks specific cancer cell features, while chemotherapy affects all rapidly dividing cells)

Chemotherapy:

• Mechanism: Chemotherapy drugs work by targeting and killing all rapidly dividing cells in the body. They interfere with cell growth and replication processes, such as DNA synthesis or cell division itself.  
• Specificity: Chemotherapy is non-specific. While it effectively kills cancer cells (which are typically fast-growing), it also damages other healthy cells that divide rapidly, such as those in hair follicles, bone marrow, and the lining of the digestive system.  
• Side Effects: Due to its non-specific nature and impact on healthy cells, chemotherapy often causes a wide range of significant side effects, including hair loss, nausea, vomiting, fatigue, weakened immune system, and mouth sores.  

Targeted Therapy:

• Mechanism: Targeted therapy drugs are designed to attack specific features or molecules within cancer cells that are crucial for their growth, survival, and spread. These targets can be specific proteins, enzymes, or signaling pathways that are either overactive or mutated in cancer cells compared to normal cells.  
• Specificity: Targeted therapy is highly specific. It aims to interfere with these specific cancer cell abnormalities, ideally leaving normal, healthy cells relatively unharmed.  
• Side Effects: Because targeted therapies are more selective, they often have fewer and less severe side effects compared to traditional chemotherapy. However, they can still have side effects, which are often related to the specific target being blocked (e.g., skin rashes with EGFR inhibitors).  

How does immunotherapy help fight cancer?

(Boosts the body’s immune system to recognize and attack cancer cells)

·  The Immune System’s Natural Role: Our immune system is constantly on the lookout for foreign invaders like bacteria, viruses, and abnormal cells, including cancer cells. It has specialized cells (like T cells and natural killer cells) that can identify and destroy these threats.  

·  Cancer’s Evasion Tactics: Cancer cells often develop ways to evade detection and destruction by the immune system. They can:  

• Hide: Express proteins on their surface that signal “don’t attack” to immune cells (immune checkpoints).  
• Suppress the immune response: Release substances that dampen the activity of immune cells in their vicinity.  
• Become less “foreign”: Lose some of the unique markers that would normally flag them as abnormal.

·  How Immunotherapy Intervenes: Immunotherapy aims to overcome these evasion tactics and enhance the immune system’s ability to fight cancer. Different types of immunotherapy work in various ways:

• Checkpoint Inhibitors: These drugs block the “off switches” (immune checkpoints) on immune cells. By releasing these brakes, the immune cells become more active and better able to recognize and attack cancer cells. Examples include drugs that target PD-1, PD-L1, and CTLA-4.  
• T-cell Transfer Therapy (Adoptive Cell Therapy): This involves taking immune cells (usually T cells) from the patient’s blood, modifying them in the lab to better recognize cancer cells, and then infusing them back into the patient. A prominent example is CAR T-cell therapy, where T cells are engineered to express chimeric antigen receptors (CARs) that target specific proteins on cancer cells.  
• Monoclonal Antibodies: Some monoclonal antibodies (laboratory-produced antibodies) can directly target specific proteins on cancer cells, marking them for destruction by the immune system. Others can block growth signals or deliver toxins directly to cancer cells.  
• Cancer Vaccines: These vaccines aim to stimulate the immune system to recognize and attack specific cancer cells. They might contain dead or weakened cancer cells, parts of cancer cells, or antigens (proteins) found on cancer cells.  
• Cytokines: These are proteins that help regulate the immune system. Some immunotherapies involve administering cytokines (like interferon and interleukin) to boost the immune response against cancer.  

·  Systemic Treatment: Like chemotherapy, many immunotherapies are systemic treatments, meaning they can target cancer cells throughout the body.