radiation therapy

Question 1

What is the dosage unit for treating with ionizing radiation?

Answer 1

Gy or Gray

Question 2

how may Gy of radiation are given to treat non melanoma skin cancer

Answer 2

30-66 Gy (or Grays)

Question 3

How many Gy are used to treat MF

Answer 3

20-40 Gy (Grays)

Question 4

How many Gy are used to treat Merkel Cell carcingom

Answer 4

50-66

Question 5

since cure rates and local control are the same for for one dose or fractionation of radiation why fractionate?

Answer 5

To decrease chronic radiation toxicity.

Question 6

How many fractions a week of radiation is normally given?

Answer 6

Five.

Question 7

Radiation works by damaging what cellular structure?

Answer 7

DNA double strand breaks cause mitotic catastrophe.

Question 8

What areas are not ideal for radiation therapy in scc.

Answer 8

areas that are edematous or at risk for poor healing such as lower leg, foot, dorsum of hand.

Question 9

what is the measurement of one gray of ionizing radiation.

Answer 9

absorption of one joule of radiation energy per kilogram of matter. Gy= J/Kg

Question 10

what age range for treatment of non melanoma skin cancer.

Answer 10

> 60 years

Question 11

What are the four general principles of radiation Tx?

Answer 11

1. > 60 yo
2. Fractionation
3. Contraindicated in Genetic disease predisposing to skin cancer and connective tissue disease.
4. Don’t re irradiate a previous radiation site.

Question 12

When might you use radiation in a melanoma?

Answer 12

1. In Situ Lentigo Maligna non surgical candidate,

2. Adjunctive or palliative treatment

Question 13

What is radiation recall?

Answer 13

Inflammatory rxn in a former radiation field following chemotherapy.

Question 14

When would someone consider Radiation Therapy RT in merkel cell carcinoma.

Answer 14

It should always be considered even after resection.

Question 15

List the radiosensitivity of skin cancers from most to least

Answer 15

SCC
BCC
Merkel cell carcinoma
Kaposi's
Angiosarcoma
Lentigo Maligna
Melanoma

Question 16

What radiation margins are recommended for MCC Merkel cell carcinoma?

Answer 16

5cm

Question 17

When might you not do adjuvant radiation tx for MCC Merkel cell carcinoma?

Answer 17

if tumor is less than 1cm and there is no immunosuppression or angiolymphatic invasion.

Question 18

What is the difference between definitive and adjuvant radiation TX

Answer 18

Definitive treatment means radiation is the sole treatment. Adjuvant means combined with another TX to reduce risk of recurrence.

Question 19

When do you give radiation tx following keloid surgery

Answer 19

within 24 hours one dose

Question 20

what percent of keloids don’t return following excision plus radiation (the long term success rate)

Answer 20

75%

Question 21

In advanced SCC adjuvent RT improved survival in which group. Entire cohort, those with perineural invasion, those with regional disease

Answer 21

Entire cohort

Question 22

What is the standard number of grays delivered with radiation treatments for each fraction.

Answer 22

1.8-2.0 Gy