••• Chapter 49^ Radiation Therapy, Chemotherapy, Immunotherapy, and Tumor Markers^491
❍ What is the target “paracentral” or “point A” dose for the treatment of nonbulky stage IB, IIA, or IIB
cervical carcinoma?
The recommended “point A” dose is 75 to 80 Gy of combined external and low-dose rate brachytherapy. One
approach would be to administer an initial 20 Gy of “whole pelvic” external beam irradiation in 2 Gy daily
fractions followed by 55 to 60 Gy to be delivered by intracavitary means. For more advanced disease, “whole
pelvic” external dose of 40 to 45 Gy and intracavitary contribution of 35 to 40 Gy is more appropriate.
❍ For which patients might extended field radiation therapy be indicated in the treatment of cervical cancer?
The tendency of cervical carcinoma to spread via a stepwise lymphatic route selects for a subset of patients whose
disease is contained within the pelvic and aortic lymph nodes outside the conventional pelvic radiation fields.
Eradication of tumor in these sites by extended field radiation therapy produces cure rates of 10% to 50%.
❍ Brachytherapy is essential to the successful treatment of cervical cancer. What doses are typically employed
to achieve this success?
The control of bulky pelvic tumor requires minimal doses of 75 to 85 Gy. These doses are not possible with
external beam radiation that would easily exceed the rectal and bladder tolerance of 60 to 70 Gy. The inverse
square law allows brachytherapy to achieve the required dose gradient over a very short distance.
❍ What isotopes are used in brachytherapy?
Radium-226 has been replaced by safer isotopes such as cesium-137 for low-dose rate intracavitary administration,
iridium-192 for interstitial, and high-dose rate administration, and cobalt-60 for some high-dose rate afterloading
applications.
❍ What are 3 indications for interstitial therapy in the treatment of carcinoma of the cervix?
The three indications for interstitial radiation therapy in cervical carcinoma are:
(1) Centropelvic recurrence after radical surgery.
(2) Distorted anatomy that makes intracavitary insertion difficult.
(3) Bulky parametrial or sidewall disease.
❍ What are the common isotopes used for interstitial implantation?
The commonly used isotopes are iridium-192 and iodine-125.
❍ Traditional low-dose rate intracavitary brachytherapy is delivered at a dose rate of 0.4 to 0.8 Gy per hour.
At what high-dose rate brachytherapy is administered?
High-dose rate irradiation is, by definition, >0.2 Gy per minute. However, the dose rate is usually much higher in
the 2 to 3 Gy per minute range.
❍ What is the role for palliative radiation therapy?
Using external irradiation single doses of 10 Gy given two to three times per week can help palliate pelvic
symptoms such as pelvic pain, vaginal bleeding and discharge, and edema.
❍ What percentage of severe complications occur following radiation therapy for carcinoma of the cervix?
In general, severe complications occur in 5% to 10% of patients being treated with radiation therapy for cancer of
the cervix. Specifically, 2% to 5% of stage IB and IIA, 5% to 10% of stage IIB, and 10% to 15% of stage III.