Methods	Multicentre RCT
Participants	Country: US 277 women were eligible for the study if they had primary stage IB squamous, adenosquamous carcinoma or adenocarcinoma of the cervix initially treated with a standard radical hysterectomy and who had negative lymph nodes but one of a specified combination of risk factors The median age at study entry was 41 years (range 20 to 80 years) All patients had primary stage IB The tumour cell type was squamous in 218 (79%) women, adenosquamous in 32 (12%) women and adenocarcinoma in 27 (10%) women GOG Performance Grade: 0: 185 (67%) women, 1: 86 (31%) women, 2: 6 (2%) women
Interventions	Arm 1: RT RT was started within 4 to 6 weeks postoperatively. Patients received external beam irradiation and no brachytherapy. The pelvic irradiation was given with a 4-field technique with a megavoltage beam, although cobalt-60 was allowed if the SSD was greater than 80 cm. Radiation dose was from 46 Gy in 23 fractions to 50.4 Gy in 28 fractions, 5 fractions per week. Each patient was to be given daily fractions of 1.80 to 2.00 Gy over 4.5 to 6 weeks. Treatment breaks for clinical problems (vomiting or diarrhoea) were allowed to total no more than 1 week Arm 2: No adjuvant chemotherapy or RT Additional details: Follow-up observation: patients were to be evaluated by physical examination, blood counts, blood chemistries and chest x-rays, every 3 months during the first 2 years of follow-up, and every 6 months during the subsequent years. Intravenous pyelogram, renal sonogram or CT scan with contrast was done at 6 months and then yearly. Results of these tests, as well as changes of therapy, adverse effects, progression or death, were reported
Outcomes	OS: HR adjusted for prognostic categories 0.74; 90% CI 0.49 to 1.12 (See GOG 92 2006) PFS Adverse events: ○ haematological ○ gastrointestinal ○ genitourinary ○ neurological
Notes	Of the 137 patients randomised to RT, 9 (6.6%) refused all RT and 6 (4.4%) refused to continue therapy after receiving less than 85% of the prescribed dose of 50.4 Gy (3.6, 3.6, 10.4, 14.4, 16.2, and 36.0 Gy). One patient discontinued RT due to an adverse reaction after receiving 21.6 Gy. In addition, 9 (6.6%) non-compliant patients had acceptable radiation doses (85% of 50.4 Gy) but in excess of 20% protraction of overall treatment time. Two other patients exceeded 20% protraction of treatment time due to an adverse reaction to the radiation requiring interruption of therapy Median length of follow-up: 10.0 years (range: 0.003 to 16 years)
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not reported, “After the eligibility criteria were verified, patients were randomly assigned to one of the two regimens: pelvic radiation or no further therapy”
Allocation concealment (selection bias)	Unclear risk	Not reported
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Not reported
Incomplete outcome data (attrition bias) All outcomes	Low risk	For grade 3 or 4 adverse events: % analysed: 268/277 (97%) women RT: 128/137 (93%) women Control: 140/140 (100%) women Analysis of overall and PFS used survival methods that allowed for loss to follow-up “There is a small but noteworthy imbalance in the follow-up between the two treatment regimens. Of those who are alive, six patients are lost-to-follow-up within the first year in the RT group while one is lost in the NFT group. Within 2 years on study, there are eight and three patients in the RT group and NFT group, respectively”
Selective reporting (reporting bias)	Unclear risk	Insufficient information to permit judgement
Other bias	Unclear risk	Insufficient information to assess whether an important risk of bias exists

Abbreviations: CT: computed tomography; FIGO: International Federation of Gynecology and Obstetrics; HR: hazards ratio; NFT: no further treatment; OS: overall survival; PFS: progression-free survival; RCT: randomised controlled trial; RT: radiotherapy; SSD: source-surface difference.