Primary radiation therapy for vulvar cancerMedical editor Kolbein Sundfør MD
Oslo University Hospital
Radiation therapy is an alternative for treatment of locally advanced vulvar cancer where surgery would be mutilating.
- Treatment for patients with locally advanced vulvar cancer, where surgery would result in colostomy or urinary conduit.
|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 for patient movements, variations in patient arrangement, and field modeling.
The extent of the tumor and possible metastases must be verified before treatment begins. Imaging of the pelvis/abdomen should be by CT or MRI. These examinations also include the kidneys/urinary tracts, therefore urography is unnecessary. MRI is the preferred diagnostic tool for the pelvis, and preferably at a designated laboratory. Adequate resolution is necessary to observe small changes.
- 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 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.
- To exclude/confirm lung metastases, a regular lung X-ray is normally adequate. However, with a high risk for lung or mediastinal metastases, such as in retroperitoneal metastases or very large tumors, a thoracic CT should be taken even if a regular X-ray is found negative (same requirement for sectional density).
Preparing the patient for external radiation therapy
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 normally starts around 10 days after CT planning.
Radiation therapy is given every day, 5 days per week. The total treatment time is about 7 weeks.
External radiation therapy
The number of treatments depends on the total dose given.
Cisplatin is given one day per week during the entire radiation treatment period, normally 6 weekly cycles, provided the patient can tolerate the treatment. If the tumor is very large, an evaluation is done later, since the tumor can shrink during treatment.
The dominating side effect is a skin reaction in the area of the vulva. The radiation field may also include the distal area of the rectum, vagina, and bladder.
Radiation to the vulva can cause:
- Radiation dermatitis of the vulva which often occurs during treatment.
- Diarrhea and abdominal pain.
- Nausea, which may be enhanced by chemotherapy.
- Irritation of the bladder mucosa leading to problems resembling urinary tract infections including frequent urination, burning, pain, and light bleeding.
Prophylactic care and patient follow-up are critical during the entire treatment period.