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Adjuvant postoperative radiation therapy for cervical cancer


Medical editor Kolbein Sundfør MD
Gynecological Oncologist
Oslo University Hospital

General

Adjuvant radiation therapy is used for patients at high risk for pelvic recurrence after an operation for cervical cancer.

Indications

Adjuvant radiation therapy after surgery for early cervical cancer is given for:

  • confirmed spreading to one or more lymph nodes
  • invasion of or short distance to resection surface
  • large tumor > 4 cm
  • deep invasion of the cervix or parametria

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 for patient movements, variations in patient arrangement, and field modeling.

Preparation

The imaging evaluation with MRI/CT should be present that covers the pelvis and lymph node stations retroperitoneal to the diaphragm.

  • 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 transversal series through the entire pelvis, simultaneous sagittal series.
  • A chest X-ray should be taken from the front and side before the operation. If the images are over two months old, new should be taken if the tumor was large or there are multiple metastases.  Any suspicious or ambiguous findings should be investigated with CT.

The radiation field covers the area of lymphatic spreading in the true pelvis. That is, from the pelvic floor and inguinal ligament to 1 cm under vertebral disc  L4-L5. The field limit is then in the disc. When a short distance to the resection limit is the only indication, the upper field limit can be made lower.

Preparing the patient

  • The radiologist will evaluate the local status. Marking may be necessary, for example, the top of the vagina. This should be done simultaneously with the referral and latest before the CT dosage plan.
  • CT dosage planning is done on a simulator at the radiation therapy unit. 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. The patient will lie on a flat examination table with only a thin mattress. The patient will be given a standard pillow 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) takes 10-12 days under normal working conditions. See CT dosage plan 

Radiation therapy normally starts around 10-12 days after CT planning.


Implementation

  • 45–50 Gy are given toward the risk area (usually 48.6 Gy)
  • Normally, 27 (25) external treatments (of 1.8-2 Gy) are given as 4 radiation fields to the pelvic area.      
  • For some patients, it may be necessary to give an additional treatment to a smaller area in 6-11 treatments. This depends on the indication for the radiation therapy. 
  • Cisplatin is given one day per week during the entire treatment period.  

Radiation therapy is given every day, five days per week. The total treatment period is about 6 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 pelvis 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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