A retrospective review of outcomes in patients with node-negative stage IB cervical cancer treated with adjuvant standard pelvic field radiation versus small field pelvic field radiation

Objective: A retrospective review was conducted to ascertain whether there are differences in outcome or complications between node-negative patients with stage IB cervical cancer who were treated with adjuvant standard field as opposed to small pelvic field radiotherapy (RT). Study design: A retrospective observational study of patients with stage IB cervical cancer treated with radical surgery between 1984 and 2010 at Groote Schuur Hospital, Cape Town, South Africa. Two different pelvic radiation field sizes were used for adjuvant post-operative RT in node-negative patients during this period: standard whole pelvic fields (WPF), or with reduced-size, "small pelvic field" (SPF) RT since 1991. These two methods reflect changes in protocol over the period of this review. Cisplatin given concurrently with radiation has been used since 1999. Cancer control and grade 3 and 4 toxicities were compared between the two groups. The aim of this study was primarily to examine whether adjuvant SPF RT is a safe approach. A literature review was conducted on the subject of post-operative adjuvant RT, especially in node-negative patients; one aim was to discover how widely the SPF approach is used throughout the world. There was no indication in the literature that this approach has been used elsewhere in South Africa. Results: The SPF technique was first advocated by Prof Neville Hacker in Australia in 1991. The first publication by his group on SPF was in 1999, followed by several subsequent retrospective reports from Asian centers. In the current audit study, 31 patients were found in the WPF group, and 56 in the SPF group. The overall 5-year survival rate was 85%. No significant differences in survival rates were found between the WPF and SPF groups (log rank p=0.67) It was found that relapse patterns did not differ between the two groups and the same applied to the crude grade 3-4 treatment morbidity rates, although two patients in the WPF group (6%) died from their complications. Conclusions: The expected benefit of the SPF approach, which targets the central pelvic tumour bed, is a reduction in small bowel morbidity and lymphoedema. It is not possible to conclude from this study whether the SPF technique is unsafe by increasing out-of-field pelvic relapses, or whether it truly reduces complications. The literature review reveals that most studies of SPF involved relatively few patients and events were infrequent, whether recurrences or morbidity. A randomized controlled trial could theoretically settle this issue but it seems unlikely ever to be performed as a large sample size would be required. Intermittent single institution, or multi-institutional pooled comparisons, with historical WPF controls seem to be the best option