Radiation Therapy: Complete Treatment Guide

Written by: Dr. Michael Chen, MD | Reviewed by: Dr. Jennifer Martinez, MD, Radiation Oncologist | Last updated: January 25, 2026

Quick Facts About Radiation Therapy

Uses high-energy rays to destroy cancer cells in a targeted area
About 50% of cancer patients receive radiation therapy at some point
Local/regional treatment - affects only the treated area, not whole body
Usually given daily Monday-Friday for 1-8 weeks
Treatment itself is painless and takes only 10-30 minutes

What is Radiation Therapy?

Radiation therapy (also called radiotherapy) is a cancer treatment that uses high-energy rays or particles to destroy cancer cells. Unlike chemotherapy which travels throughout the body, radiation therapy is a local or regional treatment that targets a specific area.

Radiation damages the DNA inside cancer cells, making it impossible for them to grow and divide. Cancer cells are particularly vulnerable to radiation because they divide more rapidly than normal cells and have less ability to repair DNA damage.

Key Points

Approximately 50% of all cancer patients receive radiation therapy during their treatment
Can be used alone or combined with surgery, chemotherapy, or immunotherapy
Precise targeting minimizes damage to healthy tissue
Modern techniques have greatly improved effectiveness and reduced side effects
Treatment is painless - you cannot see, feel, smell, or hear radiation

How Radiation Works

Radiation kills cancer cells by damaging their DNA, the genetic material that controls how cells grow and divide. There are two main ways radiation damages DNA:

Mechanisms of Action

Direct damage: Radiation directly breaks DNA strands
Indirect damage: Radiation creates charged particles (free radicals) that damage DNA

When cancer cells try to divide with damaged DNA, they die. Normal cells can also be affected, but they are generally better at repairing radiation damage than cancer cells.

Why Fractionation?

Instead of giving one large dose, radiation is typically divided into multiple smaller doses (fractions) over several weeks. This approach:

Allows normal cells time to repair between treatments
Catches cancer cells at different phases of division
Improves tumor oxygenation (oxygen makes radiation more effective)
Reduces the risk of severe side effects

Types of Radiation Therapy

External Beam Radiation (EBRT)

The most common type. A machine outside the body aims radiation at the cancer.

Linear accelerator (LINAC) delivers treatment
Painless, like getting an X-ray
Daily treatments over several weeks
No radioactivity remains after treatment

Brachytherapy (Internal)

Radioactive material placed inside or very close to the tumor.

High-dose rate (HDR): Temporary placement
Low-dose rate (LDR): Permanent or temporary
Used for prostate, cervical, breast cancers
Delivers high dose to small area

Systemic Radiation

Radioactive substances given by mouth or injection that travel through blood.

Radioactive iodine (I-131) for thyroid cancer
Radium-223 for bone metastases
Radioactive antibodies (radioimmunotherapy)
Body gives off radiation for a period of time

Intraoperative Radiation (IORT)

Radiation delivered during surgery directly to the tumor bed.

Single, concentrated dose
Used for some breast cancers
Protects surrounding tissue
Reduces total treatment time

External Beam Treatment Techniques

Technique	Description	Common Uses
3D-CRT	Three-Dimensional Conformal Radiation Therapy - beams shaped to match tumor	Prostate, lung, breast cancers
IMRT	Intensity-Modulated Radiation Therapy - varies beam intensity for precision	Head/neck, prostate, brain tumors
IGRT	Image-Guided Radiation Therapy - imaging before each treatment for accuracy	Tumors that move (lung) or near critical structures
VMAT/RapidArc	Volumetric Modulated Arc Therapy - machine rotates continuously around patient	Various cancers, faster treatment times
SBRT/SRS	Stereotactic Body/Radiosurgery - very high dose in 1-5 treatments	Small tumors, brain metastases, lung, liver
Proton Therapy	Uses protons instead of X-rays - stops at tumor with minimal exit dose	Pediatric cancers, tumors near critical organs

Understanding IMRT vs 3D-CRT

IMRT is like using a paintbrush with varying pressure to create detailed shading, while 3D-CRT is like using a stencil. IMRT allows for more precise dose distribution, especially important when tumors are near sensitive structures like the spinal cord or optic nerves.

Planning & Simulation

Before your first treatment, you'll go through a planning process to ensure radiation is delivered accurately:

Consultation (1-2 hours)

Meet radiation oncologist
Review medical history and scans
Discuss treatment plan and side effects
Answer questions and obtain consent

Simulation (30-90 minutes)

CT scan in treatment position
Custom immobilization devices made (masks, molds)
Skin marks or small tattoos placed
Sometimes additional imaging (MRI, PET)

Treatment Planning (1-2 weeks)

Radiation oncologist outlines target and organs to avoid
Medical physicist creates treatment plan
Dosimetrist calculates optimal beam angles and doses
Plan verified for safety and accuracy

First Treatment

Extra time for setup verification (30-60 minutes)
Imaging to confirm positioning
First dose delivered
Subsequent treatments faster (10-30 minutes)

Immobilization Devices

To ensure you're in the exact same position for each treatment:

Thermoplastic masks: For head/neck tumors - warm mesh molded to face
Body molds: Custom foam or vacuum cushions for torso
Breast boards: Angled boards for breast cancer treatment
Knee/ankle supports: For positioning lower body

Skin Marks and Tattoos

Small reference marks help position you correctly:

Tiny permanent tattoos (size of a freckle) - most common
Semi-permanent ink marks - can wash off over time
Marks on removable devices (masks, body molds)
Usually 3-5 marks placed during simulation

Treatment Schedule

Conventional Fractionation

The most common approach:

Frequency: Once daily, Monday through Friday
Dose: 1.8-2.0 Gy per fraction (standard dose)
Duration: 1-8 weeks depending on cancer type and goal
Weekends: Days off allow normal tissue recovery

Treatment Length by Cancer Type

Cancer Type	Typical Duration	Number of Treatments
Breast (whole breast)	3-6 weeks	15-30 treatments
Prostate	4-8 weeks	20-40 treatments
Head and Neck	6-7 weeks	30-35 treatments
Lung	3-7 weeks	15-35 treatments
Brain metastases (SBRT)	1 day - 1 week	1-5 treatments
Palliative (bone pain)	1 day - 2 weeks	1-10 treatments

Alternative Fractionation Schedules

Hypofractionation: Larger daily doses, fewer treatments (e.g., 15 treatments instead of 30)
Hyperfractionation: Multiple smaller doses per day, more total treatments
Accelerated: Treatments given twice daily to shorten overall time
SBRT/SRS: Very high doses in 1-5 treatments for small tumors

Your Radiation Therapy Team

Radiation Oncologist

Medical doctor specialized in treating cancer with radiation

Prescribes treatment plan
Monitors your progress
Manages side effects
Oversees entire treatment

Medical Physicist

Expert in radiation physics and safety

Creates treatment plan with dosimetrist
Ensures machines deliver correct dose
Performs quality assurance checks
Maintains radiation safety

Radiation Therapist

Specially trained technologist who delivers daily treatments

Positions you for treatment
Operates treatment machine
Takes daily images for accuracy
Your main daily contact

Dosimetrist

Plans treatment under physicist and oncologist supervision

Creates computer treatment plan
Calculates beam angles and doses
Optimizes plan to spare normal tissue
Works closely with physicist

Oncology Nurse

Nurse specialized in cancer care

Assesses symptoms and side effects
Provides education and support
Coordinates care with other providers
Available for questions/concerns

Support Staff

Additional team members

Social workers for emotional support
Dietitians for nutrition counseling
Patient navigators for coordination
Financial counselors for billing

Treatment Uses & Goals

Primary Treatment Purposes

Curative (Definitive)

Primary treatment to eliminate cancer

Early-stage lung cancer
Head and neck cancers
Prostate cancer
Cervical cancer

Adjuvant

After surgery to destroy remaining cancer cells

Breast cancer after lumpectomy
Brain tumors after resection
Colorectal cancer after surgery
Reduces recurrence risk

Neoadjuvant

Before surgery to shrink tumors

Rectal cancer
Some sarcomas
Makes surgery easier or possible
May allow organ preservation

Palliative

To relieve symptoms and improve quality of life

Bone pain from metastases
Brain metastases causing symptoms
Bleeding tumors
Tumors causing obstruction

Common Treatment Combinations

Chemoradiation: Chemotherapy given concurrently with radiation
- Chemotherapy sensitizes cancer cells to radiation
- Used for lung, esophageal, cervical, head/neck cancers
- More effective but increased side effects
Surgery + Radiation: Sequential or sandwich approach
- Radiation before surgery to shrink tumor
- Radiation after surgery to treat remaining cells
- Common for breast, brain, rectal cancers
Immunotherapy + Radiation: Emerging combination
- Radiation may enhance immune response
- Being studied for various cancer types
- Potential for synergistic effects

Side Effects Management

When to Call Your Doctor

Fever over 100.4°F (38°C)
Severe pain not controlled by medications
Uncontrolled nausea or vomiting
Difficulty swallowing or breathing
Signs of infection in treatment area
Persistent diarrhea or constipation
Severe skin reactions (blistering, open wounds)
Unusual bleeding or discharge

General Side Effects

Fatigue

Very Common

Cumulative tiredness that builds during treatment. Usually peaks 2-3 weeks after completion.

Energy Management →

Skin Changes

Very Common

Radiation dermatitis - ranges from mild pinkness to peeling, like sunburn

Skin Care Guide →

Loss of Appetite

Common

Decreased hunger, especially with head/neck or abdominal radiation

Nutrition Tips →

Hair Loss

Area-Specific

Only in the treatment field - not whole body like chemotherapy. Usually temporary.

Managing Hair Loss →

Area-Specific Side Effects

Head and Neck Radiation

Mucositis: Mouth and throat sores, pain with swallowing
Dry mouth (xerostomia): Reduced saliva production
Taste changes: Metallic taste, loss of taste
Dental issues: Increased cavity risk
Difficulty swallowing (dysphagia): May need feeding tube
Hoarseness: Voice changes

Chest/Breast Radiation

Esophagitis: Inflammation causing difficulty or pain swallowing
Cough: Lung irritation
Shortness of breath: Usually mild
Breast changes: Swelling, firmness, skin changes
Rib tenderness: Rarely, rib inflammation

Abdominal/Pelvic Radiation

Nausea: Stomach upset, managed with anti-nausea medications
Diarrhea: Intestinal irritation, dietary modifications help
Bladder irritation: Urgency, frequency, burning
Rectal irritation: Urgency, discomfort, bleeding (late effect)
Sexual dysfunction: May affect function and fertility

Brain Radiation

Headaches: Usually manageable with medication
Nausea: Often controlled with anti-nausea drugs
Hair loss: In treated area, usually grows back
Fatigue: Can be significant
Memory/cognitive changes: More common with whole-brain radiation
Hearing changes: If inner ear in treatment field

Timeline of Side Effects

Week 1-2: Minimal

Most people feel normal. Early skin changes may begin.

Week 3-4: Building

Fatigue increases. Skin reactions become more noticeable. Area-specific effects emerge.

Week 5-End: Peak

Side effects typically worst during final weeks and shortly after treatment ends.

1-2 Weeks Post: Continue

Effects may worsen slightly before improving. Acute effects persist.

2-4 Weeks Post: Improving

Gradual improvement. Skin heals. Energy returns slowly.

1-3 Months Post: Resolution

Most acute effects resolve. Energy continues improving for months.

Late Effects (Months to Years Later)

Some effects can develop or persist long-term:

Fibrosis: Thickening and scarring of tissue in treatment area
Lymphedema: Swelling if lymph nodes treated (arm after breast radiation)
Chronic dry mouth: Permanent reduction in saliva after head/neck radiation
Lung scarring: Radiation pneumonitis or fibrosis
Heart effects: Rare, from older breast/chest radiation techniques
Bowel/bladder changes: Chronic effects after pelvic radiation
Secondary cancers: Very rare (less than 1%), years after treatment
Fertility effects: Depends on dose and area treated

Skin Care Guidelines During Treatment

Do's for Skin Care

Wash gently with lukewarm water and mild soap

Pat skin dry, don't rub

Use only approved lotions/creams (ask your team)

Wear loose, soft cotton clothing

Protect treated area from sun (clothing, SPF 30+)

Keep skin marks visible (gentle washing only)

Don'ts for Skin Care

Don't use lotions, creams, or powders without approval
Don't use heating pads, ice packs, or hot water on treated area
Don't expose treated skin to direct sunlight
Don't use perfumes, deodorants (if underarm treated), or scented products
Don't shave treated area (electric razor only if necessary)
Don't wear tight clothing or jewelry over treatment area
Don't use adhesive tape on treated skin
Don't swim in chlorinated pools (ask your team)

Preparing for Radiation Therapy

Pre-Treatment Checklist

Complete dental work before head/neck radiation

Quit smoking (reduces treatment effectiveness and side effects)

Discuss fertility preservation if pelvic/testicular radiation

Meet with dietitian for nutrition plan

Arrange transportation for daily treatments

Plan work schedule (many people work during treatment)

Purchase approved skin care products

Build support system for practical and emotional help

Verify insurance coverage and pre-authorization

Questions to Ask Your Radiation Oncologist

What is the goal of my radiation treatment (cure, control, palliate)?
What technique will be used (IMRT, 3D-CRT, etc.)?
How many treatments will I receive and over what time period?
What are the expected short-term and long-term side effects?
How will side effects be managed?
Will I need to take time off work?
Will I receive chemotherapy at the same time?
What follow-up will I need after treatment?
How will we know if the treatment is working?
Are there any clinical trials I should consider?

Financial Planning

Contact insurance company for coverage verification
Understand copays, deductibles, and out-of-pocket maximums
Ask about payment plans if needed
Explore assistance programs (hospital financial aid, drug assistance)
Consider transportation assistance programs
Plan for lost wages if unable to work

During Treatment

What to Expect Each Day

Check-In (5 minutes)

Arrive at scheduled time
Check in at front desk
Change if needed (chest/breast treatment)

Setup and Positioning (5-15 minutes)

Therapists position you on treatment table
Use immobilization devices
Align laser lights with skin marks/tattoos
Daily imaging to verify position

Treatment Delivery (1-10 minutes)

You're alone in room but monitored via camera/intercom
Machine rotates around you or stays in fixed positions
Must remain completely still
Treatment is painless - no sensation
Machine makes whirring and clicking noises

Completion (2 minutes)

Therapists return and help you off table
No radioactivity remains in your body
Safe to be around others immediately
Schedule next appointment

Tips for Daily Treatments

Arrive on time - tight schedules with multiple patients
Wear comfortable, easy-to-remove clothing
Avoid wearing jewelry over treatment area
Use bathroom before treatment (hard to stay still)
Try relaxation techniques - breathing, meditation, visualization
Some people listen to music during treatment
Maintain routine as much as possible
Rest when needed but stay as active as tolerable

Weekly Check-Ups

You'll meet with your radiation oncologist weekly during treatment:

Review side effects and symptoms
Examine treatment area
Adjust supportive care medications
Monitor weight (especially head/neck patients)
Answer questions and provide reassurance
Make plan modifications if needed

Managing Daily Life

Work: Many people work full or part-time during treatment
Exercise: Light to moderate activity recommended, listen to your body
Diet: Maintain nutrition, may need high-calorie/high-protein diet
Hydration: Drink plenty of fluids (8+ glasses per day)
Sleep: Extra rest needed, fatigue is cumulative
Social activities: Continue as energy allows
Intimacy: Safe, but discuss concerns with your team

After Radiation Treatment

Immediate Post-Treatment (1-2 Weeks)

Side effects may continue or worsen slightly after your last treatment:

Fatigue often peaks 1-2 weeks after completion
Skin reactions may get worse before improving
Continue all skin care and supportive medications
Throat symptoms may take 2-3 weeks to improve (head/neck patients)
Stay in close contact with your radiation team

Recovery Phase (2-12 Weeks)

Gradual improvement in side effects
Skin healing completes in 3-4 weeks
Energy slowly returns - may take 3-6 months for full recovery
Hair in treatment area begins to regrow (if it will)
Appetite and taste return (varies by treatment site)
Return to normal activities as tolerated

Follow-Up Care

Regular monitoring is essential after radiation:

First visit: Usually 4-6 weeks after treatment ends
Early follow-up: Every 3-4 months for first 2 years
Ongoing surveillance: Every 6-12 months after 2 years
Imaging: CT, MRI, or PET scans as appropriate
Blood work: Tumor markers if applicable
Physical exams: Check treatment area and general health

Long-Term Health

Sun protection for treated skin (lifelong)
Report any new or persistent symptoms promptly
Monitor for late effects specific to treatment area
Maintain healthy lifestyle (diet, exercise, no smoking)
Address any psychosocial concerns (anxiety, depression)
Consider survivorship care plan

Assessing Treatment Response

How doctors determine if radiation worked:

Imaging studies compared to pre-treatment scans
Physical examination findings
Tumor marker levels (if applicable)
Symptom resolution (for palliative treatment)
Maximum response may not be seen for 3-6 months
Some changes (fibrosis) can mimic tumor on scans

Special Radiation Techniques

Stereotactic Radiosurgery (SRS) / Stereotactic Body Radiation (SBRT)

Highly precise, high-dose radiation delivered in 1-5 treatments:

Key Features

Extremely accurate targeting (sub-millimeter)
Very high dose per treatment
1-5 treatments instead of 6-8 weeks
Minimal damage to surrounding tissue
Outpatient procedure

Common Uses

Brain metastases (SRS)
Small lung tumors (SBRT)
Liver tumors (SBRT)
Spine tumors
Early-stage prostate cancer

Technologies

Gamma Knife (brain only)
CyberKnife (robotic)
TrueBeam/LINAC-based
Specialized immobilization
Real-time tumor tracking

Advantages

Much shorter treatment course
Less disruption to daily life
Fewer acute side effects
Effective for small, well-defined tumors
Option when surgery not feasible

Brachytherapy (Internal Radiation)

Radioactive sources placed directly in or near the tumor:

Types of Brachytherapy

Low-Dose Rate (LDR):
- Radioactive seeds implanted permanently
- Common for prostate cancer
- Seeds remain but lose radioactivity over months
- Single outpatient or short hospital procedure
High-Dose Rate (HDR):
- Temporary placement of radioactive source
- Source inserted via catheters, removed after treatment
- Used for gynecologic, breast, prostate cancers
- Multiple treatments over days to weeks

Common Brachytherapy Applications

Prostate cancer: LDR seed implants or HDR boost with external beam
Cervical cancer: HDR intracavitary with external beam radiation
Breast cancer: HDR for partial breast irradiation after lumpectomy
Endometrial cancer: HDR vaginal cuff treatment after hysterectomy
Head/neck cancers: Interstitial brachytherapy for select cases

Radiation Safety with Brachytherapy

LDR seeds: Minimal precautions, avoid close contact with pregnant women/children for 2 months
HDR: Source removed after each treatment, no radioactivity remains
You won't make others radioactive with most brachytherapy
Follow specific instructions from your radiation team

Proton Therapy

Advanced form of external beam radiation using protons instead of X-rays:

How It Differs

Protons stop at tumor - no exit dose
X-rays pass through body
Better sparing of tissue behind tumor
Potentially fewer side effects

Best Candidates

Pediatric cancers (reduce late effects)
Tumors near critical structures (brain, spine)
Eye tumors (uveal melanoma)
Skull base tumors
Some prostate cancers

Limitations

Limited availability (fewer centers)
Very expensive
Not clearly superior for many cancers
Insurance may not cover
May require travel to specialized center

Treatment Experience

Similar to standard radiation
Same planning and simulation
Daily treatments
Painless
Similar acute side effects

Frequently Asked Questions

Will I be radioactive after external beam radiation?

No. External beam radiation does not make you radioactive. The radiation passes through your body during treatment but doesn't remain. You're safe to be around others, including children and pregnant women, immediately after treatment.

Is radiation painful?

The radiation treatment itself is completely painless - you won't feel, see, smell, or hear anything during the actual beam delivery. However, side effects from radiation (like skin irritation or sore throat) can cause discomfort, which can be managed with medications.

Can I drive myself to radiation treatments?

Most people can drive themselves to radiation treatments. However, if you're receiving concurrent chemotherapy, have significant fatigue, or are on certain pain medications, you may need someone to drive you. Discuss with your radiation oncologist.

Why do I need radiation if the tumor was completely removed by surgery?

Even after successful surgery, microscopic cancer cells may remain in the area that are too small to see or remove. Adjuvant radiation therapy targets these remaining cells to reduce the risk of cancer coming back (recurrence).

Will I lose all my hair?

Unlike chemotherapy, radiation only causes hair loss in the specific area being treated. If you're receiving radiation to your head, you'll lose hair in that area. Breast or prostate radiation will not cause hair loss on your head. Hair usually grows back after treatment ends.

Can I work during radiation treatment?

Many people continue working during radiation therapy, either full-time or with adjusted schedules. It depends on your job type, how you feel, and the treatment site. Fatigue is cumulative, so you may need to reduce hours later in treatment.

How is radiation different from chemotherapy?

Radiation is a local treatment that targets a specific area, while chemotherapy is systemic and travels throughout the body. Radiation uses high-energy rays; chemotherapy uses drugs. Side effects differ - radiation affects mainly the treated area, while chemotherapy can affect the whole body.

What if I miss a treatment day?

Missing one or two treatments is usually not a problem - your team will reschedule you. However, prolonged treatment gaps can reduce effectiveness because cancer cells may regrow. If you must miss treatments, discuss with your radiation oncologist how to make them up.

Will radiation cause me to get cancer in the future?

There is a very small risk (less than 1%) of developing a second cancer from radiation therapy, typically many years later. However, this risk is far outweighed by the benefit of treating your current cancer. Modern techniques minimize radiation exposure to healthy tissue.

Can I get radiation therapy more than once to the same area?

It depends on the area and previous dose. Some areas (like skin) tolerate repeat radiation well. Others (like the spinal cord) have strict lifetime dose limits. Your radiation oncologist will assess whether re-irradiation is safe and appropriate if cancer recurs.

Why do I need tattoos?

The small permanent tattoos (about the size of a freckle) are reference marks that help position you exactly the same way for each treatment. Precise positioning ensures radiation hits the tumor and avoids healthy tissue. Temporary marks can fade or wash off.

Will I feel tired during treatment?

Fatigue is the most common side effect of radiation therapy and affects most patients. It typically builds during treatment, peaks during the last 1-2 weeks and shortly after completion, then gradually improves over 2-3 months. The fatigue is different from normal tiredness and doesn't always improve with rest.

Can I exercise during radiation treatment?

Yes, exercise is generally encouraged during radiation therapy. Light to moderate activity (walking, swimming, yoga) can actually help with fatigue and mood. Listen to your body and adjust intensity as needed. Avoid activities that cause excessive sweating in the treatment area if you have skin irritation.

How soon after radiation will I know if it worked?

Radiation continues working for weeks to months after treatment ends. Initial response assessment is usually done 4-8 weeks after completion with a scan and physical exam. Maximum tumor shrinkage may not occur until 3-6 months post-treatment. Your oncologist will explain the expected timeline for your specific cancer.

Should I avoid being around others during treatment?

With external beam radiation, no precautions are needed - you're not radioactive. With brachytherapy, temporary precautions may be advised (especially with permanent seed implants). Your team will provide specific instructions if any restrictions apply.

Related Resources

Medical Disclaimer: This information is educational only. Treatment decisions should be made with your oncology team based on your specific situation.