head and neck

Question 1

describe accelerated repopulation

Answer 1

• kicks in for head and neck tumors after 28 days
• have to compensate with larger dose if treatment longer than 28 days
• reason for BID in head and neck

Question 2

what is accelerated fractionation

Answer 2

same dose delivered in shorter time

Question 3

what is medical creep in head and neck

Answer 3

as patient loses weight, nodes may sweep from surface into body; dose may miss nodes as anatomy shrinks

Question 4

doctor says patient getting bad skin reaction. What could have gone wrong in plan?

Answer 4

-was PTV cropped from skin for optimization? If not, VMAT will try to push high dose to surface- will get very high dose at gradient surface. Then, if patient is slightly off, can get bad skin reaction due to the high dose gradient

Question 5

patient loses 1 cm weight along neck. Is plan still ok?

Answer 5

with VMAT, TMRs would be higher by 3%/cm all around the neck- dose to target probably high by 3 %. If only one small section has 1 cm loss, the contribution will be less significant

Question 6

describe DAHANCA trial

Answer 6

Danish head and neck cancer group
investigated HART (hyperfractionated accelerated radiotherapy)- 76 Gy/ 56- 10 fractions weekly 
-supports the understanding that hyperfractionation does not cause added late toxicity, even when combined with moderate acceleration and dose escalation as in this study.

Question 7

MACH-NC meta-analysis

Answer 7

• meta-analysis of chemotherapy in head and neck cancer
• looked at benefit of addition of chemotherapy in terms of overall survival in head and neck squamous cell carcinoma
• chemo-radiation most effective for node-positive and locally advanced H/N patients

Question 8

some common H/N fractionations

Answer 8

• often 3 levels- 70 (gross disease), 63 (lymph nodes), or 56 (low risk) in 35 fractions
• re-irradiation with gross disease is 60/50 BID daily
• 60,54/30

Question 9

how do you crop the PTV for optimization and evaluation in H/N?

Answer 9

3 mm for optimization

5 mm for eval

Question 10

what are shims used for?

Answer 10

under patient head in thermoplastic mask

-can be removed if patient swells

Question 11

what to avoid entering through with H/N

Answer 11

shoulders, bite blocks

Question 12

side effects of RT in head and neck

Answer 12

dry mouth

trouble swallowing

Question 13

side effects of RT in head and neck

Answer 13

dry mouth
trouble swallowing
hearing loss
hypothyroidism
speech
cataracts
weight loss

Question 14

what is usualy PTV margin

Answer 14

3 mm

Question 15

describe intra oral cone

Answer 15

cone goes into mouth to collimate beam

Question 16

historical treatment for larynx includes…

Answer 16

wedges

Question 17

CBCT match structure

Answer 17

-H/N patients have 1 cm in and 1 cm out mach structure

Question 18

what is bolus made of?

Answer 18

• superflab

- 3D = polylactic acid, acrylonitrile butadiene

Question 19

what is contrast used for in esophagus?

Answer 19

to delineate the GTV, normal esophagus, and stomach

• in CT, perform density override on oral contrast
• assess impact on TP and decide if override should be used

Question 20

fractionations for esophagus

Answer 20

• 50 Gy/25
• 54 Gy/30
• 45 Gy/25

Question 21

CTV and PTV margins in esophagus

Answer 21

CTV is GTVnodes + 10 mm, GTVprimary + 5 to 40 mm depending on tumor location and GI movement
-PTV is CTV + 5 mm if 4DCT, 10 to 15 mm if no 4DCT

Question 22

larynx vs pharynx

Answer 22

larynx is top of trachea

pharynx is top of esophagus

Question 23

typical immobilization etc

Answer 23

thermplastic mask
bolus
bit bloxk (to keep mandible in correct positon)

Question 24

is swallowing a concern?

Answer 24

No, happens for small part of treatment time

Question 25

when is RT performed after surgery?

Answer 25

If more > 15 % chance of involvement

-generally treat 1 cm beyond where surgeons were

Question 26

OAR constraints for 2 Gy fx

Answer 26

PRV brainstem Dmax < 60 Gy
PRV spinal cord Dmax < 50 Gy
brain DMAX , 35 gY
PRV optic struture Dmax < 45 Gy
lens Dmax < 4 Gy
parotid glands mean < 26 Gy
at least 20 cc of combined parotid volume < 20 Gy
mandible max dose < 105 % inside PTV and < 100 % outside PTV
mandible mean dose < 45 Gy
brachial plexus max dose < 63 Gy
cochlea dmax < 45 Gy
lips mean < 20 Gy
lips max < 30 Gy
oral cavity mean < 30 Gy
oral cavity max < 60 Gy
contralateral submadnibular gland mean < 39 Gy
esophagus mean < 45 Gy
oropharynx mean < 45 Gy

Question 27

why use 6 MV in H/N

Answer 27

so many interfaces- interface effects worse with higher MV

Question 28

describe CHART

Answer 28

continuous hyperfractionated accelerated radiation therapy
36 fractions in 12 days, 3 fx per day at 6 h intervals, 54 Gy total
-conventional is 70/35 in 7 weeks

hyperfractionation so would expect less late effects
-however saw myelopathies (6 h maybe not long enough for repair to occur)

tumour control was similar to conventional

can’t directly compare BED because treatment time so different

Question 29

what does BED not take into account?

Answer 29

cell proliferation

Question 30

EORTC trial

Answer 30

European organization for research and treatment of cancer

• 72 Gy/45 fx (3 fx/day) with 2 week rest period in middle
• convetional is 70/35

-expected more acute effects - saw this

• expected less late effects but actually saw bad late effects
• late effects either from such acute effects, or 6 h is not enoufh time for repair