Edel 1

Andrew Edel

Dos 531 Clinical Oncology for Med Dos

Head and Neck with Lymphatics

How was this patient positioned for simulation? What positioning devices/accessories were used, how and why?

The patient was simulated supine with arms resting at sides with the head extended. Legs were

over a ‘roll’ for comfort. The central axis was place on the right tonsil. A bite block, Aquaplast

mask, and accuform cushion were used as immobilization devises.

Discuss the target dose as defined by your physician and the rationale behind the total dose and fractionation regimen. Include any references or current research to help answer the question.

Three PTV were provided. 70Gy to the gross tumor 60Gy to surrounding tissue with a possibility

of invasion and 54Gy to cervical nodes level 2-4. This treatment will be delivered in 33 fractions.

This dose and schedule has been shown to provide up to 24% reduction in local failure, however

the many factors involved in possible schedules makes research standardization very difficult.1

What specific avoidance structures were contoured? Include a screen shot of your contoured target and organs at risk. Create and embed a table of OAR tolerance doses based on your physician prescription and include any associated QUANTEC values. List the contraindications if tolerance doses were to be exceeded.

Avoidance structures contoured: left and right parotid (aqua and seafoam), mandible (orange),

brain stem (navy blue), oral cavity (tan), spinal cord (green), spinal cord with expansion (dark

green), larynx (gold), esophagus (contour not visible), and lens of eyes (not pictured, still

contoured but outside of field).

PTV structures are shaded: PTV1 (red, 70 Gy), PTV2 (pink, 60 Gy), and PTV3 (yellow-green,

54 Gy, lymphatics).

Edel 2

This list was provided by the physician as tolerance goals:

Edel 3

This list shows all constraints used to evaluate the plan:

Relevant Quantec Recommendations:2

Critical Structure Volume Dose/Volume

Max Dose Toxicity Rate

Toxicity Endpoint

Brain stemD1-10 cc <= 59 Gy

<54 Gy

<64

<5%<5%<5%

Neuropathy or necrosis

Spinal cord 50 Gy60 Gy69 Gy

0.2%6%50%

Myelopathy

Parotid, BilateralBilateralUnilateral

MeanMeanMean

<=25 Gy<=39 Gy<=20 Gy

<20%<50%<20%

Long term salivary function <25%

Pharyngeal constrictors

Mean <=50 Gy <20% Symptomatic dysphagia and aspiration

LarynxMeanMeanV50

<50 Gy<44 Gy<27%

<66 Gy <20%<30%<20%<20%

Vocal dysfunctionAspirationEdemaEdema

Esophagus MeanV35V50V70

<34 Gy<50%<40%<20%

5-20%<30%<30%<30%

Grade 3+ esophagitisGrade 2+ esophagitisGrade 2+ esophagitisGrade 2+ esophagitis

Edel 4

Identify any involved lymph nodes in your treatment region. Embed a screen shot of the nodal regions with corresponding labels.

Bilateral level II-IV cervical nodes were included in treatment.

Use your IMAIOS Subscription: http://www.imaios.com/en and other anatomy references to describe the anatomical “boundaries” (physical limits) of the area treated. Embed a diagram and/or screen shot of your CT data to point out the boundaries.

The superior treatment boarder is the inferior nasopharynx, soft pallet, and hard pallet. The

anterior boarder includes an approximately 3cm expansion anterior to the PTV2 and include fall

off to the anterior neck. The posterior boarder includes the vertebral bodies but not the spinal

cord or posterior spinous processes. The VMAT technique allows these areas to be spared while

treating lymphatics that reach further posterior as they move out laterally. The lateral boarders

include fall off to the whole neck thickness. The inferior boarder is the level of the collar bone.

Edel 5

Describe, in detail, the radiation treatment technique used to treat this anatomical region.

This treatment was accomplished using a VMAT technique with 2 arcs. For spinal cord sparing

Massey Cancer Center (MCC) does not use 360 degree arcs. Instead the CW arch starts with a

gantry angle of 218 degrees and delivers radiation at 4 degrees increments for 72 positions

ending at 142 degrees. The CCW arc begins at 140 degrees so each of the 71 positions at 4

degree intervals will be unique from the CW arc. The end position of the gantry for the CCW arc

is 220. This provides 143 beam positions with 2 degree intervals for the computer to optimize.

The collimator angle is 345 degrees for the CW arc and 15 degrees for the CCW. This is to

feather out scatter dose from MLC leakage.

The process of planning first involves prioritizing dose for the original contoured structures. This

gives a general impression of what needs to be done. Pseudo-structures were then created in

order to give the planner more objective points to leverage dose. For example, a ring structure

was placed around the PTV with a dose limit that is consistent with dose fall off. This goal works

with the other objectives and pushes the plan to being more conformal. Next contours were made

around hot spots and an objective was added to cool these spots down. This increases dose

homogeneity.

Edel 6

Include a final DVH of your treatment plan with appropriate labels and discuss your ability to meet the target and OAR tolerance guidelines.

All constraints were meet except the .5cm expansion around the spinal cord reached 46.24 Gy

instead of 45 Gy the goal. This was deemed acceptable because this is a small increase in dose,

the area exceeding this dose was less than .01cc, and because it is within an expansion rather

than a contoured area risk is minimal. This was a standard case and there were no major

obstacles in meeting constraints.

Edel 7

References:

1. Saunders, MI. Head and Neck Cancer: Altered Fractionation Schedules. The Oncologist. 1999;4(1): 11-16.http://theoncologist.alphamedpress.org/content/4/1/11.full.pdf+html

2. Bentzen SM, Constine LS, Deasy JO, et al. Quantitative Analyses of Normal Tissue Effects in the Clinic (QUANTEC): An Introduction to the Scientific Issues. International Journal of Radiation Oncology. 2010;76(3): S3-S9. https://doi.org/10.1016/j.ijrobp.2009.09.040