A phase III randomized trial of postoperative pelvic irradiation in stage IB cervical carcinoma with poor prognostic features: Follow-up of a gynecologic oncology group study

Purpose: To investigate, in a phase III randomized trial, whether postoperative external-beam irradiation to the standard pelvic field improves the recurrence-free interval and overall survival (OS) in women with Stage IB cervical cancers with negative lymph nodes and certain poor prognostic features treated by radical hysterectomy and pelvic lymphadenectomy. Methods and Materials: Eligible patients had Stage IB cervical cancer with negative lymph nodes but with 2 or more of the following features: more than one third (deep) stromal invasion, capillary lymphatic space involvement, and tumor diameter of 4 cm or more. The study group included 277 patients: 137 randomized to pelvic irradiation (RT) and 140 randomized to observation (OBS). The planned pelvic dose was from 46 Gy in 23 fractions to 50.4 Gy in 28 fractions. Results: Of the 67 recurrences, 24 were in the RT arm and 43 were in the OBS arm. The RT arm showed a statistically significant (46%) reduction in risk of recurrence (hazard ratio [HR] = 0.54, 90% confidence interval [CI] = 0.35 to 0.81, p = 0.007) and a statistically significant reduction in risk of progression or death (HR = 0.58, 90% CI=0.40 to 0.85, p = 0.009). With RT, 8.8% of patients (3 of 34) with adenosquamous or adenocarcinoma tumors recurred vs. 44.0% (11 of 25) in OBS. Fewer recurrences were seen with RT in patients with adenocarcinoma or adenosquamous histologies relative to others (HR for RT by histology interaction=0.23, 90% CI=0.07 to 0.74, p  = 0.019). After an extensive follow-up period, 67 deaths have occurred: 27 RT patients and 40 OBS patients. The improvement in overall survival (HR = 0.70, 90% CI=0.45 to 1.05, p = 0.074) with RT did not reach statistical significance. Conclusions: Pelvic radiotherapy after radical surgery significantly reduces the risk of recurrence and prolongs progression-free survival in women with Stage IB cervical cancer. RT appears to be particularly beneficial for patients with adenocarcinoma or adenosquamous histologies. Circumstances that may have influenced the overall survival differences are considered.