Impact of pelvis irradiation on toxicity of further oxaliplatin-based chemotherapy in rectal cancer.

Abstract

777 Background: Radiotherapy is used in the neoadjuvant setting in majority of rectal cancer patients, while its effect on overall survival is limited mostly to patients with threatened resection margin. Preoperative pelvic irradiation might damage bone marrow. In consequence, relative dose intensity (RDI) and efficacy of further adjuvant or palliative CT might be reduced. The aim of the study was to assess whether radiation damage to the pelvic bone marrow influences the tolerance of further oxaliplatin-based CT. Methods: We have performed the cohort analysis of patients with adenocarcinoma of rectum or colon receiving FOLFOX-4 chemotherapy in adjuvant or palliative setting between 2011-2016. Oxaliplatin relative-dose intensity (RDI) within 8 weeks from the beginning of CT was calculated for each patient. The major factors, which can reduce oxaliplatin RDI, were analyzed independently (hemathological toxicity, neurological toxicity, occurrence of hypersensitivity reactions to oxaliplatin). The data regarding the first disruption of oxaliplatin dose within all planned courses of FOLFOX-4 was also collected. Results: 220 patients met eligibility criteria. 41 of them received neoadjuvant radio(chemo)therapy (study group), the remaining 179 patients were assigned to control group (n = 179). RDI did not differ significantly between irradiated and non-irradiated patients (p = 0.794). There were no statistically significant differences in observed oxaliplatin-related toxicities. The median time between the start of chemotherapy and the first disruption of oxaliplatin administration was also not statistically different between the two groups (p = 0.156). Conclusions: An impact of preoperative radio(chemo)therapy on RDI or tolerance of FOLFOX was not found in rectal cancer.