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Adjuvant postoperative radiation therapy of the vulva


Medical editor Kolbein Sundfør MD
Gynecological Oncologist
Oslo University Hospital

General

Adjuvant radiation therapy of patients at high risk for recurrence after surgery.

Indication

  • High risk for recurrence after surgery

Goal

  • Cure the disease

Definitions

Target volume

 

Target volume definitions from ICRU
(International Commission on Radiation Units and Measurements)
GTV (Gross tumor volume) Palpable or visible/identifiable area of malignant growth. 
CTV (Clinical target volume) Tissue volume which contains GTV and/or subclinical microscopic malignancy.
ITV (Internal Target Volume) Volume containing CTV and one inner margin taking into account inner movements and revisions of CTV.
PTV (Planning Target Volume) Geometric volume containing ITV and one Setup margin taking into account assumed variations in patient movements, variations in patient arrangement, and field modeling.

 


Preparation

MRI and CT examinations covering the pelvis and lymph node stations retroperitoneally to the diaphragm should be available before treatment is started. 

  • CT examination: CT must be taken with optimal image quality (no low-dose protocol). A multichannel CT must be used with thin sections (0.6 mm to maximally 3 mm). The CT should be reformatted into three dimensions. In general, the CT should be taken with intravenous contrast and exposure no later than the portovenous phase. Water should be used for contrast medium in the bowel.
  • MRI examination: For transversal, sagittal, or parasagittal series, the sectional thickness should be no more than 4 mm. Minimum T1 and T2-weighted through the entire pelvis, simultaneous sagittal series.
  • A lung X-ray from the front and side should be taken before the operation. If the images are over two months old, new images are taken for large tumors or multiple metastases. Suspect or ambiguous findings are examined with lung CT.  

The radiation field cover the area of potentially lymphogenic spreading in the pelvis. That is, from the floor of the pelvis to the inguinal ligament to 1 cm under vertebraL4-L5 where the field limit is in the vertebra. When a short distance to the resection margin is the only indication, the upper field limit can be made lower.

Preparation for the patient

  • The treating radiologist will assess the status of the tumor locally. Marking is done, for example, of the top of the vagina. This should be done simultaneously at referral, and at the latest before the CT dosage planning. 
  • CT dosage planning is done on a simulator. It is very important the patient is well medicated for pain and is able to lie still on her back for 20-30 minutes. If necessary, 1-2 g of paracetamol can be given as premedication. An extra dose of opiates may also be necessary for patients receiving this. The patient will lie on a flat examination table with only a thin mattress. The patient will be given a standard pillow to place under her knees and one under her head. This positioning must be identical to the position used for the treatment apparatus.
  • Intravenous contrast is used routinely. Patients taking metformin-type drugs such as metformin or glucophage must not take these at least two days before dosage planning. 
  • Planning of the radiation field (tracing, determination of radiation field, necessary adjustments, checks, and documentation for the simulator) usually takes 10-12 days.

Radiation therapy will start around 10-12 days after the CT dosage plan.


Implementation

  • A dosage of 45–50 Gy is administered to the area at risk.
  • Normally, 27 (25) external treatments of 1.8-2 Gy in 4 radiation fields are given to the pelvic area.     
  • For some patients, it may be necessary to give indvidualized supplementary treatment. 
  • Cisplatin is given one day per week during the entire treatment.   

Radiation therapy is given every day, five days per week. The total treatment period is about six weeks.


Follow-up

Most side effects occurring during treatment are due to healthy organs included in the radiation field. This includes parts of the small and large intestine, bladder, upper vagina, lymph nodes, ovaries, pelvic bone, and uterus.

Radiation therapy to the vulva can lead to:

  • Diarrhea and abdominal pain.
  • Nausea, which may be enhanced by chemotherapy
  • Fatigue
  • Irritation of bladder mucosa. This leads to problems resembling urinary tract infections including frequent urination, burning, pain, and light bleeding. 
  • Bone marrow changes
  • The vaginal mucosa may be dry/sore and stenoses may occur in the vagina. Since the ovaries are situated in the field of radiation, the ovaries will stop producing hormones and the patient will start menopause. Hormone substitution may be given to younger patients.
  • Skin reactions are rare. If this should occur, it is usually in the gluteal fold.

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