A method of providing external beam therapy, known as intensity modulated radiation therapy (IMRT), may be a significant therapeutic development. This technique uses computer-generated algorithms that accurately distinguish between target treatment volumes and normal tissue. The radiation beam intensity is modulated to optimize the delivery of radiation to the specified treatment volume while sparing adjacent normal tissue. The result appears to be much more accurate treatment of the tumor with minimal toxicity. Emphasizing this point is a study in 40 gynecologic cancer patients in which IMRT was used. Excellent coverage of the planned treatment volume was obtained, with no patient suffering grade 3 toxicity, and only 60% of patients suffering grade 2 toxicity, compared with a historical rate of 90% toxicity with conventional techniques (120). This technique is especially promising for treating cervical cancer because it allows higher doses to be delivered much more precisely, allowing patients who are unable to undergo brachytherapy because of pelvic anatomy and tumor geometry a chance for curative therapy. Studies utilizing IMRT in treating patients with cervical cancer are limited, but experience with this technique is increasing. Initial papers comparing the two techniques report decreased toxicity with comparable locoregional control, but they do not have long-term data on 5-year survival rates, so this technique is yet to be validated (121).
Adjuvant Radiation In an effort to improve survival rates, postoperative radiotherapy was recommended for patients with high and intermediate risk factors such as metastasis to pelvic lymph nodes, invasion of paracervical tissue, deep cervical invasion, or positive surgical margins (76,86,89,90,106,111,112,122). Although most authors agree that postoperative radiotherapy is necessary in the presence of positive surgical margins, the use of radiation in patients with other high risk factors is controversial. Increasing evidence supports the use of adjuvant radiation. Particularly controversial, but best studied, is the use of radiation in the presence of positive pelvic lymph nodes. The rationale for treatment is the knowledge that pelvic lymphadenectomy does not remove all of the nodal and lymphatic tissue and subsequent radiotherapy can eradicate microscopic disease. The hesitancy to recommend postoperative radiotherapy derives from the significant rate of postradiation bowel and urinary tract complications (123). Most of the available data are retrospective. However, a randomized study by the GOG comparing radiation with no further treatment for patients at high risk for recurrence with negative pelvic nodes revealed a 30% serious complication rate, 16% reoperation rate, and a 2% mortality rate as a result of treatment-related complications (124).
Based on retrospective studies, it appears that postoperative radiation therapy for positive pelvic nodes can decrease pelvic recurrence but does not improve 5-year actuarial survival rates. One multi-institutional study showed no difference in survival in patients with three or fewer positive pelvic nodes (59% versus 60%) (112). However, there seemed to be a benefit when radiotherapy was given to those with more than three positive nodes.