Treatment Planning

Question 1

Where is point A, and what should it correspond to anatomically?

What is Point B?

Answer 1

• Point A is 2 cm above the external cervical os and 2 cm lat to the central canal/ tandem. This should correspond to the paracervical triangle, where the uterine vessels cross the ureter.
• Point B is 5 cm lat from the midline at the same level as point A (2 cm above the external cervical os). It is supposed to represent the obturator nodes. The dose to point B is usually

Question 2

Before CT-based planning, how were the bladder, rectum, and vaginal points defined for cervical cancer brachytherapy?

Answer 2

• Before CT-based planning, the bladder point was 5 mm behind the post surface of the Foley balloon on a lat x-ray filled with 7 cc radiopaque fluid and pulled down against the urethra. The rectum point was 5 mm behind the post vaginal wall between the ovoids at the inf point of the last intrauterine tandem source or mid vaginal source. The vaginal point was the lat edge of the ovoids on AP film and mid ovoid on lat film. In the present age of CT planning, an alternative is to contour the organs and calculate the max dose to the organ using 3D planning.

Hristov, Borislav; Lin, Steven H.; Christodouleas, John P. (2014-07-11). Radiation Oncology - A Question Based Review (Kindle Locations 11519-11523). LWW. Kindle Edition.

Question 3

What are the dose limits to the bladder, rectum, and vaginal points in cervical cancer brachytherapy?

Answer 3

In cervical cancer brachytherapy, typically the max allowed dose to the rectal point is 75 Gy, the max bladder point dose is 80 Gy, and the max vaginal dose is 120 Gy. With 3D planning, dose limit to 2cc of bladder is £ 90 Gy equivalent 2Gy dose (EQD2) (normalized therapy dose), rectum dose to 2cc (D2cc) £ 75 Gy EQD2. (Viswanathan A et al., Brachy 2012)

Question 4

What RT dose can cause ovarian failure? What about sterility?

Answer 4

• Ovarian failure can occur with 5– 10 Gy of RT. Sterility can occur after 2– 3 Gy.

Question 5

What are the typical LDR and HDR in cervical cancer Tx?

Answer 5

• In cervical cancer brachytherapy, LDR is usually 0.4– 0.8 Gy/ hr, while HDR is much higher, at least 12 Gy/ hr. Typically, 1 treatment of 5.5– 6.0 Gy takes approximately 5– 10 min to deliver.

Question 6

What should be the dose to point A in RT for cervical cancer (sum of EBRT + brachytherapy)? Does it depend on the stage of dz?

Answer 6

• In cervical cancer radiotherapy, the cumulative dose to point A should be at least
• 75 Gy for stage IA Dz,
• 80– 85 Gy for stages IB– IIB Dz, and
• 85– 90 Gy for stages III– IVA Dz, so staging is a factor in determining the dose.
• For most patients with stage IB2 or higher disease, point A dose should be at least 80 Gy and point B dose should be at least 55 Gy. In cervical cancer, Tx of inguinal nodes should be considered if Dz involves the lower 3rd of the vagina.

Question 7

Describe the borders of typical AP and lat fields in cervical cancer Tx.

Answer 7

• AP field
  
  • sup to L4-5 or L5/ S1,
  • inf to 3 cm below the most inf vaginal involvement or inf obturator foramen,
  • and lat 2 cm from the pelvic rim.
  • Lat beams would have the same sup and inf extent, with the ant edge to 1 cm ant of the pubic symphysis and post edge to include the entire sacrum.
  • For common iliac nodal involvement, extend the field to cover up to L2.
  • For P-A nodal involvement, extend the field to the top of T12.
  • The borders can be tailored for early-stage vs. more advanced Dz.
• In the CT planning era, the alternative is to contour the organs and nodes of interest to ensure adequate coverage.

Question 8

Typical EBRT Rx for Cervical CA

Answer 8

Typically, cervical cancer pts treated with EBRT rcv RT to the WP to 45 Gy in 1.8 Gy/ fx. Sidewall boosts usually go to 50– 54 Gy. Persistent or bulky parametrial tumors usually rcv 60 Gy. P-A nodes go to 45 Gy if treated. Bulky nodes go to 60 Gy with 3D-CRT or IMRT.

Question 9

Does overall Tx time in cervical cancer impact outcome? Ideally, how long should the RT Tx take?

Answer 9

Yes. Prolonged overall RT Tx time in cervical cancer is associated with poorer outcomes. Ideally, EBRT and brachytherapy should be completed within 7 wks. The effect is more notable in more advanced-stage pts (stages III– IV).

56 DAYS!

Question 10

Procedure-related complications seen in cervical cancer intracavitary brachytherapy:

Answer 10

1. Uterine Perforation (<3%)
2. Vaginal Perforation (<1%)
3. DVT (<1%)

Question 11

Name the most common acute side effects associated with RT for cervical cancer.

Answer 11

Skin irritation, fatigue, hemorrhoids, colitis-diarrhea, cystitis-frequency/ dysuria, and nausea are all possible acute side effects from cervical cancer RT.

Question 12

Name the common long-term side effects associated with cervical cancer RT.

Answer 12

• Common long-term side effects of cervical cancer radiation include permanent alteration in bowel habit, menopause in the premenopausal age group, chronic cystitis with frequency, and vaginal stenosis with dyspareunia and postcoital bleeding. The major severe long-term toxicities are most commonly bowel related: rectosigmoid stenosis, requiring possible colostomy, and major rectal bleeding. Hematuria, ureteral stricture, fistula, SBO, and hip fracture or sacral insufficiency fracture can also occur.

Hristov, Borislav; Lin, Steven H.; Christodouleas, John P. (2014-07-11). Radiation Oncology - A Question Based Review (Kindle Locations 11626-11630). LWW. Kindle Edition.

Question 13

What should pts do regularly to prevent vaginal stenosis after receiving RT for cervical cancer?

Answer 13

Vaginal Dilator routine use