Prophylactic extended-field irradiation of para-aortic lymph nodes in stages IIB and bulky IB and IIA cervical carcinomas. Ten-year treatment results of RTOG 79-20.

OBJECTIVES: To investigate whether irradiation to the standard pelvic field only improves the response rate and survival in comparison with pelvic plus para-aortic irradiation in patients with high-risk cervical carcinoma, and to investigate patterns of failure and treatment-related toxicity.

DESIGN: Randomized controlled trial from November 1979 to October 1986, with stratification by histology, para-aortic nodal status, and International Federation of Gynecology and Obstetrics (FIGO) stage.

SETTING: Radiation Therapy Oncology Group (RTOG) multicenter clinical trial.

PATIENTS: A total of 367 patients with FIGO stage IB or IIA primary cervical cancers measuring 4 cm or greater in lateral diameter or with FIGO stage IIB cervical cancers were randomized to RTOG protocol 79-20 to receive either standard pelvic only irradiation or pelvic plus para-aortic irradiation.

INTERVENTION: Pelvic only irradiation consisted of a midplane pelvic dose of 40 to 50 Gy in 4.5 to 6.5 weeks with daily fractions of 1.6 to 1.8 Gy for 5 d/wk. Pelvic plus para-aortic irradiation delivered 44 to 45 Gy in 4.5 to 6.5 weeks with daily fractions of 1.6 to 1.8 Gy for 5 d/wk. A total dose of 4000 to 5000 mg/h of radium equivalent or 30 to 40 Gy was provided by intracavitary brachytherapy to point A.

MAIN OUTCOME MEASURES: Response rate, overall and disease-free survival, patterns of failure, and treatment-related toxicities.

RESULTS: Ten-year overall survival was 44% for the pelvic only irradiation arm and 55% for the pelvic plus para-aortic irradiation am (P = .02). Cumulative incidence of death due to cervical cancer was estimated as significantly higher in the pelvic only arm at 10 years (P = .01). Disease-free survival was similar in both arms; 40% for the pelvic only arm and 42% for the pelvic plus para-aortic arm. Locoregional failures were similar at 10 years for both arms (pelvic only, 35%; pelvic plus para-aortic, 31%; P = .44). In complete responders, the patterns of locoregional failures were the same for both arms, but there was a lower cumulative incidence for first distant failure in the pelvic plus para-aortic irradiation arm (P = .053). Survival following first failure was significantly higher in the pelvic plus para-aortic arm (P = .007). A higher percentage of local failures were salvaged long-term on the pelvic plus para-aortic arm compared with the pelvic only arm (25% vs 8%). The cumulative incidence of grade 4 and 5 toxicities at 10 years in the pelvic plus para-aortic arm was 8%, compared with 4% in the pelvic only arm (P = .06). The death rate due to radiotherapy complications was higher in the pelvic plus para-aortic arm (four [2%] of 170) compared with the pelvic only arm (one [1%] of 167) (P = .38). The proportion of deaths due to radiotherapy complications in the pelvic plus para-aortic arm was higher than in the pelvic only arm (four [6%] of 67 vs one [1%] of 85; P = .24). If the patient had abdominal surgery prior to para-aortic irradiation, the estimated cumulative incidence of grade 4 and 5 complications was 11%, compared with 2% in the pelvic only arm.

CONCLUSIONS: The statistically significant difference in overall survival at 10 years for the pelvic plus para-aortic irradiation arm, without a difference in disease-free survival, can be explained by the following two factors: (1) a lower incidence of distant failure in complete responders and (2) a better salvage in the complete responders who later failed locally.