What are the guidelines for vaginal contouring?

Vaginal Contouring Guidelines for Radiation Therapy

For vaginal contouring in radiation therapy, the vulvar clinical target volume (CTV) should be defined as the gross tumor volume (GTV) or tumor bed plus the adjacent skin, mucosa, and subcutaneous tissue of the vulva excluding bony tissue, with a wire placed clinically to define the vulvar skin borders during CT simulation. 1

Target Volume Definition and Contouring

• Any gross vulvar disease should be contoured as a GTV and include any visible and/or palpable extension into the vagina 1
• The vulvar CTV target should exclude bony tissue while including the GTV or tumor bed plus adjacent skin, mucosa, and subcutaneous tissue 1
• A wire placed clinically to define the vulvar skin borders and the GTV during CT simulation is essential for accurate planning 1
• Markers on the anus, urethra, clitoris, and wiring of any scars will significantly aid in planning 1
• To ensure adequate distal margin on the vulvar target volume, a "false structure" or bolus should be placed over the vulva for treatment planning purposes 1

Technical Considerations

• CT or MRI planning with possible image fusion technology should be used to ensure adequate dosing and coverage 1
• Radio-opaque markers should be placed on key landmarks during simulation to assist in defining the primary target volume 1
• Doses to target areas should be confirmed using thermoluminescent dosimeter (TLD) at the first treatment 1
• The inferior vulvar border should be at least 2 cm below the most distal part of the vulva 1
• Care should be taken to spare the femoral heads and necks during planning 1

Nodal Contouring Guidelines

• Symmetrical geometric expansions on vessels should NOT be used for the inguinofemoral nodes 1
• The inguinofemoral nodal CTV should extend:
  • Laterally from the vessels to the medial border of the sartorius and rectus femoris muscles 1
  • Posteriorly to the anterior vastus medialis muscle 1
  • Medially to the pectineus muscle or 2.5-3 cm medially from the vessels 1
  • Anteriorly to the anterior border of the sartorius muscle 1
• The caudal extent of the inguinofemoral nodal basin is the top of the lesser trochanter of the femur 1
• The pelvic nodal CTV includes the bilateral external iliac, obturator, and internal iliac nodal regions with a minimum of 7 mm symmetrical expansion excluding bone and muscle 1

Margin Recommendations

• The groin CTV volume should not extend outside the skin and should be trimmed by 3 mm in the absence of skin involvement 1
• With skin involvement, the CTV should extend to the skin with bolus material applied during treatment 1
• Planned treatment volume (PTV) expansion is typically 7-10 mm 1
• Image-guided IMRT should be considered in select cases to account for vulva edema or marked tumor regression 1

Treatment Planning Considerations

• Planning should respect normal tissue tolerances including rectum, bladder, small bowel, and femoral head and neck 1
• Bolus should be used to ensure adequate dosing to superficial target volumes 1
• For highly selected cases where only a superficial vulvar target is to be treated, an enface electron beam may be used 1
• Doses range from 50.4 Gy in 1.8 Gy fractions for adjuvant therapy to 59.4-64.8 Gy in 1.8 Gy fractions for unresectable disease 1
• In select cases, large nodes may be boosted to a dose of approximately 70 Gy 1

Post-Treatment Considerations

• Patients who have received RT for vulvar cancer may experience vaginal stenosis and dryness 1
• Vaginal dilators may be beneficial for patients experiencing symptoms of vaginismus and/or vaginal stenosis 1
• Dilator use can start 2-4 weeks after completion of RT and can be performed indefinitely 1
• Patients should receive education on sexual health and vaginal health, including regular vaginal intercourse and/or vaginal dilator use 1
• The use of vaginal moisturizers/lubricants (e.g., estrogen creams, nonhormonal options) should be recommended 1

Common Pitfalls to Avoid

• Failing to place wire markers during simulation, which are essential for accurate target delineation 1
• Using symmetrical geometric expansions on vessels for inguinofemoral nodes, which is explicitly not recommended 1
• Inadequate bolus application, which can lead to underdosing of superficial target volumes 1
• Failing to account for vulvar edema or tumor regression during treatment, which may require image-guided approaches 1
• Not respecting normal tissue tolerances, which can lead to unnecessary toxicity 1

By following these guidelines, radiation oncologists can ensure consistent and appropriate contouring for vaginal/vulvar radiation therapy, which is critical for optimizing treatment outcomes while minimizing morbidity and preserving quality of life 2.