Impact of pelvic bone marrow irradiation on the hematological toxicity of subsequent chemotherapy in rectal cancer.

Preoperative radio(chemo)therapy in rectal cancer may irreversibly damage pelvic bone marrow (PBM) and impair the tolerance of subsequent chemotherapy. The aim of the study was to assess the relationship between the irradiated volume of PBM and the toxicity of subsequent 5-fluorouracil, oxaliplatin, leucovorin (FOLFOX-4) in rectal cancer. We included consecutive rectal cancer patients who received FOLFOX-4 postoperatively or due to cancer relapse. The PBM was divided into iliac (IM), lumbosacral (LSM), and lower pelvic (LPM) marrow. We assessed mean dose, and percentage of volume receiving 10%-90% (V10%-V90%) of the prescribed dose for PBM, IM, LSM, and LPM. Generalized linear model for repeated measures (GLM) was used to test an influence of dose-volumes distribution on toxicities grade 2 or higher (TOX2) and grade 3 or higher (TOX3). The two-sided t-test was used to evaluate the difference in mean dose, mean V20%, and mean V40% between patients who experienced TOX2 or TOX3 and those who did not. 39 patients met eligibility criteria. Because of the low occurrence of TOX3 (n=3), related analyses were abandoned. We found no influence of dose-volume distribution on TOX2 in GLM and no significant differences in mean dose, mean V20%, and mean V40% for PBM, IBM, LSM, and LPM between patients who experienced TOX2 and those who did not. To conclude, no relationship between doses received by PBM in preoperative radio(chemo)therapy in rectal cancer and hematological tolerance of subsequent FOLFOX-4 chemotherapy was found.