Clinical Oncology Assignment

Directions: Divide the following anatomical areas amongst your group members and complete the following assignment. For groups with 4 members you may choose 2 primary tumors in the same area (head and neck, chest, or pelvis) but they should not be the same tumor site.

•Primary Head and Neck with lymph nodes

•Primary Lung/Mediastinum or Breast/chest wall with lymph nodes

•Primary Pelvis (any tumor found below L4-L5) with lymph nodes

Find a case in your clinic that you have worked on, or are working on, to research and answer the corresponding questions (Note: this can be a case that your clinical instructor is planning or planned but you observed/participated). Please include any references and helpful screenshots to describe your rationale and to explain the treatment plan design and process.

Questions:

1. How was this patient positioned for simulation? What positioning devices/accessories were used, how and why? (5 points)

The patient was simulated head first, supine, with a wing board and a 4-inch pillow under their knees. The legs were straight with an O-ring on the feet to keep them stabilized. The arms were up, and a half body vacuum lock bag was utilized for reproducible setup. The arms were up so the preaortic region was not blocked during treatment.

2. 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. (5 points)

The target dose was for this patient was 45 Gy to be delivered in 1.8 Gy fractions and a total of 25 fractions. This was a stage IIIC1 endometrioid adenocarcinoma of the uterus. The uterus was removed along with nodes of the external and internal iliac although the resident thinks they may have removed a common iliac node. There was no involvement of the surrounding organs (cervix, ovaries, or fallopian tubes). The left and right internal and external iliac was positive for disease and were removed. The resident did not believe there was any gross disease left and was comfortable not delivering a dose to 50 Gy, administering any type of boost and there was no need for Brachytherapy. The patient will begin chemo in coordination with the radiation treatment. At the physician’s discretion, radiation treatment for the entire pelvis and preaortic field can be 45 Gy in 25 fractions or 50.4 Gy in 30 fractions per ROTG 12031.

3. 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. (20 points)

The high priority organs at risk as defined by the treatment plan which is aligned with ROTG 12031 is as follows. The constraints from the physician are below, all plans at my clinic are checked by Mobius with their defined objectives.

OAR

QUANTEC Value2,3

Physician

Contraindications

Rectum

V75<15%

V30 Gy < 60%

Grade 3+. Bleeding, diarrhea.

Bladder

V65<50%

V45 Gy < 40%

Grade 3+. Cystitis

Femur L/R

Femoral Heads: V50 , 5% (RTOG)

V30 < 15%

Fracture

Bone Marrow

TD 5/5 30 Gy (2/3)

V10 < 90%, V20 < 75%

Temporary decrease in number of stem cells.

Spinal Cord

Max Dose 50 Gy

V50 Gy < .01cc

Myelopathy

Cauda Equina

Max Dose 60 GY (Emani)

V50 Gy < .01cc

Neurotoxicity

Kidney L/R

Mean < 15-18 Gy, V12 < 55%

Dmean < 15 Gy, V12 Gy < 50%, If mean to one kidney > 18 Gy dose to remaining V6 Gy < 30%.

Clinical dysfunction. Nephritis

Small Bowel

V45<195cc

Bowel Bag V52 < 1cc*

*Constraint over target*

V40 < 30%

Grade 3 +. Perforation/fistula.

Below is a 3-view screen shot of all contoured structure for this plan.

The full list of structures contoured for this treatment plan include:

4. Identify any involved lymph nodes in your treatment region. Embed a screen shot of the nodal regions with corresponding labels. (15 points)

The lymph nodes in the pelvic region are highlighted well by the following screen shot.

From the planning system, here is a coronal view showing the pelvic vessel contour that has a margin of .7 cm.

5. Use your IMAIOS Subscription: http://www.imaios.com/en (Links to an external site.)Links to an external site. and other anatomy references to describe the anatomical “boundaries” (physical limits) of the area treated. (examples: hard palate, nasal choanae). Embed a diagram and/or screen shot of your CT data to point out the boundaries. (20 points)

Standard pelvic regions include:1

Superior Border: A transverse line between L4 and L5

Inferior Border: Transverse line below the lowest extent of the obturator foramen

Lateral Border: 2 cm lateral to widest true bony pelvic diameter.

With this case involving lymph nodes, the superior border extends to the top of L3 to include the bottom region of the preaortic nodes and includes the S3 vertebrae posteriorly. The inferior border of the obturator foramen remains the same and the field was to include at least 3 cm of the vagina.

6. Describe, in detail, the radiation treatment technique used to treat this anatomical region. (20 points)

Examples: Technique type (VMAT, IMRT, Conformal), VMAT-Number of arcs, their direction, collimator rotations, number of degrees. Beam angles, couch rotations, field design, wedges, use of split fields, etc. Include all specific setup information to describe your process.  Include any screen shots to help describe your plan design.

The treatment was delivered using a Siemens Helical Tomography (HT) machine delivering 1.8 Gy in 25 fractions with MU’s equaling 6,523. The number of gantry rotations were 23.6 for a duration of 474.5 seconds. The couch speed was .05374 cm/second and traveled 25.5 centimeters. The final prescription was 96% of the PTV receives at least 45 Gy.

Typically, 5 cm jaws are used to reduce treatment time, but it proved too difficult to meet the constraints, so it was switched to 2.5 cm jaws. Priorities (importance) were adjusted for the organs at risk to meet the constraints issued by the physician. The bowel bag, rectum, bone marrow and bladder were all given high priorities compared to the other structures. The bladder and bowel bag proved to be the most difficult constraints, the PTV that was targeted encompassed 23% of the bladder but the constraint was eventually met. You can see the priority of 50 versus 10 to the other structures (PTV is a 500)

The use of an inner and outer ring structures was utilized to “drive” dosages to regions of tight boundaries and to create uniformity of dose to the PTV. The rings also prevent leakage dose to surrounding tissue. The inner ring was created for 30 Gy and over while the outer ring was for 30 Gy and under.

7. Include a final DVH of your treatment plan with appropriate labels and discuss your ability to meet the target and OAR tolerance guidelines. (15 Points)

As mentioned earlier, the final prescription was 96% of the PTV receives at least 45 Gy. All of the constraints were met except for the bowel bag which received a dose of 40 Gy of slightly more than the 30% constraint but only went over by a few percent. The large area the PTV covered and the large size of the bowel bag made it extremely difficult to overcome the constraint. The physician knew this would be an issue and created the constraint of a max dose to the bowel bag of 53 Gy that took priority over coverage to the target. The max dose for the bowel bag in this plan was 47.83 Gy. The organs at risk results are below.

OAR

Physician Constraints

DVH Results

Rectum

V30 Gy < 60%

30 Gy to 34%

Bladder

V45 Gy < 40%

40 Gy to 32.5%

Femur L/R

V30 < 15%

30 Gy < 5%

Bone Marrow

V10 < 90%, V20 < 75%

10 Gy to 85%

20 Gy to 75%

Spinal Cord

V50 Gy < .01cc

Max Dose 34 Gy

Cauda Equina

V50 Gy < .01cc

Max Dose 42.5%

Kidney L/R

Dmean < 15 Gy, V12 Gy < 50%, If mean to one kidney > 18 Gy dose to remaining V6 Gy < 30%.

12 Gy to 17%

Small Bowel

Bowel Bag V52 < 1cc*

*Constraint over target*

V40 < 30%

Max Dose 47.83 Gy

40 Gy to 32.7%

References:

1. Klopp A, Yeung A, et al. RTOG 1203: A RANDOMIZED PHASE III STUDY OF STANDARD VS. IMRT PELVIC RADIATION FOR POST-OPERATIVE TREATMENT OF ENDOMETRIAL AND CERVICAL CANCER (TIME-C). Published 3/16/15. Accessed 03-1-19.

2.Radiation Oncology/Toxicity/QUANTEC. Wikibooks. https://en.wikibooks.org/wiki/Radiation_Oncology/Toxicity/QUANTEC. Accessed March 2nd 2019.