The Influence of Pelvic Bone Dose-volume Parameters on Bone Marrow Suppression During Radiation Therapy in Patients With Stage I to III Rectal Cancer Based on Real-world Data.

PURPOSE

The aim of this study was to evaluate the effect of pelvic bone dose-volume parameters on bone marrow suppression during radiation therapy (RT) in patients with rectal cancer stage I to III disease receiving either neoadjuvant radiation therapy (neo-RT) or curative-intent radiation therapy (cur-RT).

METHODS AND MATERIALS

This was a retrospective study with data mined from an electronic medical record review at a single institution. Between January 2016 and September 2022, patients with rectal cancer who consecutively received neo-RT or cur-RT in our department were included. The data collected included complete baseline peripheral blood counts and hematologic toxicity (HT) data collected during RT. The radiation dose-volume parameters of 3 pelvic bone marrow subsites (iliac bone marrow [IBM], lumbosacral bone marrow, and lower pelvis bone marrow) were collected. The primary endpoint was grade ≥ 2 HT (HT2+), including leukopenia, neutropenia, anemia, thrombocytopenia, and total HTs. Logistic regression was employed to analyze the associations of HT2+ with dosimetric parameters and clinicopathologic characteristics. Receiver operating characteristic curves and the area under the curve (AUC) were generated to verify the prediction efficacy of the pelvic bone dose-volume parameters combined with clinicopathologic indices.

RESULTS

A total of 130 patients with stage I to III rectal cancer with complete clinical data were included. During neo-RT and cur-RT, 57 (43.8%) of these patients experienced HT2+. Multivariate analysis revealed that gender, the IBM-Dmean, the IBM-V15, and the IBM-V40 were significantly associated with grade 2+ leukopenia ( < .05), and the AUC of gender combined with the IBM-Dmean, the IBM-V15, and the IBM-V40 in predicting grade 2+ leukopenia was 0.834. The optimal cutoff values were an IBM-Dmean = 2692.75 cGy, an IBM-V15 = 86.65%, and an IBM-V40 = 20.75%. Patients who received oxaliplatin-containing concurrent chemotherapy (ChT) regimens were more likely to experience grade 2+ thrombocytopenia ( = .054). The AUC of concurrent ChT regimens in predicting grade 2+ thrombocytopenia was 0.678. Female gender was significantly associated with grade 2+ anemia and total HT2+ status.

CONCLUSIONS

Among patients with rectal cancer stage I to III disease who received neo-RT or cur-RT, female patients with higher IBM-Dmean, IBM-V15, and IBM-V40 were more likely to experience grade 2+ leukopenia, and oxaliplatin-containing concurrent ChT regimens were identified as a potential factor for increasing the incidence of grade 2+ thrombocytopenia.