Dosimetric predictors of acute hematologic toxicity in cervical cancer patients treated with concurrent cisplatin and intensity-modulated pelvic radiotherapy

PURPOSE: To identify dosimetric parameters associated with acute hematologic toxicity (HT) and chemotherapy delivery in cervical cancer patients undergoing concurrent chemotherapy and intensity-modulated pelvic radiotherapy. METHODS AND MATERIALS: We analyzed 37 cervical cancer patients receiving concurrent cisplatin (40 mg/m(2)/wk) and intensity-modulated pelvic radiotherapy. Pelvic bone marrow (BM) was contoured for each patient and divided into three subsites: lumbosacral spine, ilium, and lower pelvis. The volume of each region receiving 10, 20, 30, and > or =40 Gy (V(10), V(20), V(30), and V(40), respectively) was calculated. HT was graded according to the Radiation Therapy Oncology Group system. Multivariate regression models were used to test associations between dosimetric parameters and HT and chemotherapy delivery. RESULTS: Increased pelvic BM V(10) (BM-V(10)) was associated with an increased Grade 2 or worse leukopenia and neutropenia (odds ratio OR], 2.09; 95% confidence interval CI], 1.24-3.53; p = 0.006; and OR, 1.41; 95% CI, 1.02-1.94; p = 0.037, respectively). Patients with BM-V(10) > or =90% had higher rates of Grade 2 or worse leukopenia and neutropenia than did patients with BM-V(10) <90% (11.1% vs. 73.7%, p < 0.01; and 5.6% vs. 31.6%, p = 0.09) and were more likely to have chemotherapy held on univariate (16.7% vs. 47.4%, p = 0.08) and multivariate (OR, 32.2; 95% CI, 1.67-622; p = 0.02) analysis. No associations between HT and V(30) and V(40) were observed. Dosimetric parameters involving the lumbosacral spine and lower pelvis had stronger associations with HT than did those involving the ilium. CONCLUSION: The volume of pelvic BM receiving low-dose radiation is associated with HT and chemotherapy delivery in cervical cancer patients undergoing concurrent chemoradiotherapy.