Comparison of 2 Contouring Methods of Bone Marrow on CT and Correlation With Hematological Toxicities in Non–Bone Marrow–Sparing Pelvic Intensity-Modulated Radiotherapy With Concurrent Cisplatin for Cervical Cancer

Abstract

ObjectivesTo compare volumes and dose volume histogram (DVH) parameters for bone marrow contours using 2 methods on computed tomography (CT) and correlation with grade 2 or higher hematological toxicity (HT) in patients with cervical cancer treated with non–bone marrow–sparing intensity-modulated radiotherapy (IMRT) with concurrent cisplatin.Materials and MethodsThe planning CT scans of 47 patients prospectively enrolled and treated with IMRT arm of a phase 2 trial (NCT00193804) contoured for pelvic bone marrow in 2 sets; whole bone (WB), and freehand (FH) inner cavity of bone. Various subvolumes were made in each set—sacrum, ilium, ischium, lower pelvis, lumbosacral spine, sacrum, and whole pelvis—and compared for volume and DVH parameters (V10, V20, V30, and V40) using paired t test. The hematological parameters during RT compiled from electronic database analyzed for higher than grade 2 (Radiation Therapy Oncology Group) HT and correlated with DVH parameters using log regression analysis (P < 0.05 significant).ResultsThe FH subvolumes were 25% to 30% of WB. The mean DVH parameters V10, V20, V30, and V40 for whole-pelvis FH and WB were 86.5%, 77.5%, 62.5%, and 40.5%; and 88%, 79.6%, 62.9%, and 40%, respectively. There was significant difference between the DVH parameters of 2 sets (P < 0.05) for all subvolumes except ischium V20, sacrum V10, and lumbosacral spine V10. The leukopenia, neutropenia, anemia, and thrombocytopenia higher than grade 2 was seen in 53%, 29.8%, 65.9%, and 10.6%, respectively. The mean V10 for whole pelvis was less than 90% for both sets. On both univariate and multivariate analyses, only FH whole pelvis V40 more than or equal to 40% correlated with higher than grade 2 leukopenia (Mann-Whitney U test, P = 0.026) and neutropenia (P = 0.05) with odds ratio, 4 (95% confidence interval, 1.166–13.728; P = 0.028).ConclusionsThe FH bone marrow cavity volume is a better surrogate of active bone marrow on CT images and correlated with higher than grade 2 HT (V40 >40%). Further prospective studies validating significance of high-dose effects and identifying correlation of bioimaging with CT contouring are warranted.