Objectives: To 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 methods: The 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 (V(10), V(20), V(30), and V(40)) 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).
Results: The FH subvolumes were 25% to 30% of WB. The mean DVH parameters V(10), V(20), V(30), and V(40) 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 V(20), sacrum V(10), and lumbosacral spine V(10). The leukopenia, neutropenia, anemia, and thrombocytopenia higher than grade 2 was seen in 53%, 29.8%, 65.9%, and 10.6%, respectively. The mean V(10) for whole pelvis was less than 90% for both sets. On both univariate and multivariate analyses, only FH whole pelvis V(40) 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).
Conclusions: The FH bone marrow cavity volume is a better surrogate of active bone marrow on CT images and correlated with higher than grade 2 HT (V(40) >40%). Further prospective studies validating significance of high-dose effects and identifying correlation of bioimaging with CT contouring are warranted.