Radiation Planning

Question 1

Describe the whole pelvic RT field for endometrial cancer. What total doses are typically prescribed?

Answer 1

Borders of the whole pelvis (WP) RT field for endometrial cancer:

• Superior: L4-5 or L5/ S1
• Inferior: bottom of obturator foramen
• Lateral: 1.5– 2.0 cm lateral to pelvic brim
• Anterior: front of pubic symphysis
• Posterior: split sacrum to S3

Treat to 45– 50 Gy.

Question 2

What is the border of an extended RT field for endometrial cancer, and when should extended fields be used?

Answer 2

The sup border of an extended RT field for endometrial cancer is T10-11 or T11-12. It should be used if there are positive P-A LNs.

Question 3

According to the American Brachytherapy Society (ABS), what are the Tx site and depth for vaginal cuff brachytherapy for endometrial cancer?

Answer 3

According to the ABS, for endometrioid carcinoma of the endometrium, the proximal 3– 5 cm of the vagina (approximately one-half) should be treated. For CCC, UPSC, or stage IIIB, the target is the entire vaginal canal. Prescribe to 0.5 cm beyond the vaginal mucosa. (Nag S, IJROBP 2000)

Question 4

What LDR and HDR are typically used for adj intracavitary RT alone for endometrial cancer?

Answer 4

For adj intracavitary RT therapy alone, the LDR is 50– 60 Gy over 72 hrs (0.7– 0.8 Gy/ hr). The HDR is 21 Gy (7 Gy × 3) at 0.5 cm depth. Many different fractionation schemes exist 6x 5 Gy, 5.5 Gy x 4 to 0.5 Cm

Question 5

What LDR and HDR are commonly used for adj intracavitary RT given with WP RT for endometrial cancer?

Answer 5

When given in combination with WP RT, LDR doses of 30– 40 Gy and HDR doses of 10– 15 Gy (5 Gy × 2 or 3) at 0.5 cm depth are commonly used.

Question 6

Brachytherapy Technique

Answer 6

• Consider placing radioopaque seed or clip at vaginal apex
• largest cylinder that fits comfortably
• minimize movement from placement, planning, treatment
• Larger cylinder more dose to to 5mm (2cm cylinder 5mm dose is 60 % vs. 3cm, 68%, 4cm 71%)

Question 7

How are nonbulky vaginal cuff recurrences treated in endometrial cancer pts with no prior RT?

Answer 7

For nonbulky vaginal cuff recurrences in pts with no prior RT, a combination of pelvic RT and brachytherapy is typically used. Treat to 45 Gy pelvic RT and assess the response. If the residual is < 0.5 cm, add HDR vaginal brachytherapy at 7 Gy × 3 to 0.5 cm depth of the vaginal mucosa. (Nag S et al., IJROBP 2000)

Question 8

How are vaginal cuff recurrences that are bulky or within a previously irradiated field treated in endometrial cancer pts?

Answer 8

For endometrial cancer pts with vaginal cuff recurrences that are bulky (> 0.5 cm thickness) or in a previously irradiated field, consider interstitial brachytherapy or IMRT.

Question 9

When do inguinal nodes need to be included in the RT fields for endometrial cancer?

Answer 9

In cases with distal vaginal involvement, the entire vagina and inguinal nodes need to be included in EBRT fields.

Question 10

How should inoperable endometrial cancer be treated with RT?

Answer 10

Consider pelvic RT to 45 Gy → intracavitary RT boost using 2 tandem intrauterine applicators to 6.3 Gy × 3 prescribed to 2-cm depth (serosal surface). If pelvic RT is contraindicated, consider definitive intracavitary RT alone (7.3 Gy × 5 prescribed to 2-cm depth). (Nag S et al., IJROBP 2000)

Question 11

What is the RT tolerances of proximal and distal vagina?

Answer 11

The RT tolerance of the mucosa of the proximal vagina is 120 Gy and distal vagina is 98 Gy. (Hintz BL et al., IJROBP 1980)

Question 12

At what RT dose does ovarian failure occur?

Answer 12

Ovarian failure occurs after 5– 10 Gy.

Question 13

At what RT dose does sterilization occur in women?

Answer 13

Sterilization in women occurs after 2– 3 Gy.

Question 14

What are the expected acute and late RT toxicities associated with RT Tx for endometrial cancer?.

Answer 14

Acute toxicities: diarrhea, proctitis, abdominal cramps, fatigue, bladder irritation, drop in blood counts, n/ v

Late toxicities: vaginal dryness and atrophy, pubic hair loss, vaginal stenosis and fibrosis (recommend vaginal dilators), urethral stricture, fistula formation, SBO, chronic urinary and bowel frequency

Question 15

Does IMRT help vs. 3DCRT for pelvic radiation? What studies support this

Answer 15

• RTOG 0418 new atlas defines obturator nodal region, eliminates bony land marks, recommendation for common illiacs and para-aortic CTV
• Decreases small bowel toxicity 40-95%, bladder toxicity 23-30%, rectal toxicity 23-66%
• RTOG 0418 (Jhingran et al. Phase II study IMRT Primary endpoint: feasability? yes , secondary end points: G2 and higher small toxicity decreased 40% to 28% with IMRT but not powered
• TIME-C Standard vs. IMRT pelvis in postop endometrial and cervical CA Accruing right now
  
  • RCT Phase III with pelvic rt +/- chemo to IMRT vs. 4 field box
  • Primary Acute GI toxicity in IMRT
  • Secondary: acute grade 2, Grade 3

Question 16

Post Treatment Complications

Answer 16

Quality of Life

• PORTEC 1
• Remained close to toilet for urinary control: 26% vs. 10% no tx
• Urinary Incontinence 30% vs. 16%
• Limitatinos of daily activity related to bowel 26 vs 15%
• BUT 52% 4 field (complication 21%, 18% 3 field 36%, and 30% Ap/PA (30%)
• p=0.06 for technique and complication rate

Vaginal Length

• Cervical 7.5 pre to 6.25 after 2 years , 9cm endometrial to 7.5 2 yrs post

Secondary Malignancies

• Brown IJROP 2010 EBRT + Brachy 1.22 vs. no radiation 0.92 ORR
• PORTEC 1 after 13.3 yrs 19% secondary primary (22 vs. 16 NS)
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