Long-term results of randomized studies on the use of a gentamicin-collagen sponge in rectal cancer – depending on the length of time between the completion of radiotherapy and the surgery

Introduction. Two randomized studies on the use of a gentamicin-collagen sponge (GRM01/1997 and GRM02/2007) in rectal cancer surgery showed a statistically significant decrease in the rate of distant metastases in the experimental group and a similar rate of local recurrences. The objective of the presented study was a retrospective evaluation of the effect of the GRM use on the observed rate of generalized recurrences, disease-free survival (DFS), overall survival (OS) and cancer-specific survival (CSS) – depending on the length of the interval between radiotherapy and surgery. Materials and methods. The study comprised 239 patients, included previously into randomized studies, in whom the 5 x 5 Gy radiotherapy was used. In 204 people, the surgery was made within 7 days of the completion of radiotherapy (group A). The remaining group of 35 patients were operated on after 4–8 weeks (group B). The follow-up period was 5 years. The statistical analysis was made with the Kaplan-Meier test. The value of α = 0.05 was degfined as the threshold of statistical significance. Results. In both groups, there were no statistical differences between the patients operated on with the use of GRM and those operated on without the use of GRM. The analysis took into consideration the most significant parameters, which could affect the oncological results, (ypTNM, lympho-vascular invasion (LVI), blood vessel invasion (BVI). In group A, the use of GRM was connected with a lower rate of metachronic distant metastases (p = 0.002; RR 0.41; 95% CI [0.24–0.72]), the prolongation of DFS (p = 0.008; HR 2.16; 95% CI [1.20–3.83]) and of CSS (p = 0.010; HR 2.37; 95% CI [1.20–4. 67]). No such relationships were observed in group B. Conclusions. The use of GRM decreases the risk of distant metastases and has an influence on the prolongation of recurrence free survival, but only when surgery is carried out within 7 days of the completion of irradiation.