ABCs of Radiation Therapyfor Patients, Family and Friends

David Kozono, MD, PhD

What is radiation therapy?

• For lung cancer, radiation therapy is most often X-rays given externally using multiple beams that converge on the part of the body with tumor.

• X-rays cannot be felt, seen, heard or otherwise perceived during treatment.

How is radiation given?

• Using a linear accelerator (linac)

source of radiation

robotic table

• Patient positioning using tattoos

How is radiation aimed?

http://www.rtanswers.org

• Patient positioning using tattoos

How is radiation aimed?

http://xkcd.com/933/

How is radiation aimed?

• Imaging to assure treatment accuracy and precision

X-rays for dailyverification ofpositioning

CT for weeklyconfirmationof targetlocalization

How is radiation aimed?

PositioningX-rays

CT:Plan

CT:Week 5

Lung cancer infiltrates “normal” tissues

Cancer

Emphysematous Lung

3 cmCancer

GTV

CTV

PTV

GTV = gross tumor volume; CTV = clinical target volumePTV = planning target volume

Treatment volumes

GTVGTV

CTV

PTV

Organs at risk

rightlung

leftlung

esophagus

spinal cord

The challenge

unavoidableoverlap of target volumeand esophagus

Radiation beams

Radiation dose

Expected side effects

skin reddening

very rare risk ofspinal cord injury

pain with swallowing

lunginflammation

Why are there so many treatments?

• A course is anywhere from a single treatment for symptom relief, up to seven weeks of daily treatment Monday–Friday for cure

• Fractionation– Dividing radiation dose into multiple sessions– Spares healthy tissues more than tumors

Why are there so many treatments?

Cancer cellsLittle sparing with fractionation

Long-term side effectsSignificant sparing with fractionation

1 x 2 Gy 1 x 4 Gy

0 2 4 86 1210

Fractionated

1 x 2 Gy 1 x 4 Gy Fractionated

6 x 2 Gy

3 x 4 Gy

6 x 2 Gy

3 x 4 Gy

Dose (Gy)

Surv

ival

frac

tion

(log)

Common questions and answers

• Am I radioactive after treatment (safe around young children)?– For about 0.000000000000000001 seconds– So, no…perfectly safe

Common questions and answers

• Can you tell if the tumor is shrinking?– The daily X-rays ± weekly CT scans are mostly

to verify positioning and tumor targeting.– Tumors continue to shrink for weeks after the

final treatment.– We therefore typically perform scans about two

months after completion of therapy.

Common questions and answers

• Will you be repeating the treatment?– Unlike chemotherapy, we typically administer a

single course of treatment.– If needed, additional treatment can be given on

a case-by-case basis weighing the benefits and risks.

Common questions and answers

• Is all this radiation, including X-rays and CT scans, safe?– Rate of second cancers due to radiation is less

than 1 in 100 and likely closer to 1 in 1000.– Side effects depend on the area of the body that

is treated; treatment will only be given if the benefits will likely outweigh the risks and the risks are acceptable.

Resources

• Department website– http://www.dana-farber.org/Adult-Care/Treatment-and-

Support/Treatment-Centers-and-Clinical-Services/Department-of-Radiation-Oncology.aspx

• American Society for Radiation Oncology– http://www.rtanswers.org/

• LUNGevity– http://www.lungevity.org/about-lung-cancer/lung-cance

r-101/treatment-options/radiation-therapy