| Purpose Radiotherapy plays an important role in the treatment of cervical cancer and rectal cancer. And concurrent radiochemotherapy is the standard treatment for locally advanced cervical cancer and rectal cancer with stage II and III. Concurrent radiochemotherapy meanwhile increases acute hematologic toxicity. Previous studies showed that limiting the volume of pelvic bone marrow reduces acute bone marrow toxicity in cervical cancer patients undergoing concurrent chemotherapy. However, the most accurate dosimetric parameters that could predict acute hematologic toxicity are still uncertain. In the present study, we investigated dosimetric parameters associated with acute hematologic toxicity(HT) in cervical cancer and rectal cancer patients treated with pelvic intensity-modulated radiotherapy(IMRT) alone or concurrent chemotherapy.Methods We retrospectively analyzed 167 patients(97 with cervical cancer and 70 with rectal cancer) receiving concurrent radiochemotherapy(n=107) or pelvic IMRT alone(n=60). Pelvic bone marrow(BM) was contoured for each patient. We calculated the volume of pelvic BM receiving 5, 10, 20, 30, 40, 50Gy(V5, V10, V20, V30, V40 and V50, respectively) and the mean doses of pelvic bone marrow. Bone marrow suppression within 3 months after the start of radiotherapy was collected. Acute HT was graded according to the RTOG system. χ2 test was used to test the correlation between the volume of bone marrow irradiation from 5 to 50Gy(V5-V50), the mean doses of pelvic bone marrow and acute HT for patients treated with pelvic IMRT alone or chemoradiotherapy. In addition, univariate and multiple logistic regression analysis were performed to correlate the risk of Grade 2 HT and the aforementioned predictors(age, gender, stage, pathology, volume of bone marrow irradiation, number of chemotherapy cycles, cancer site, with surgery, concurrent chemotherapy or consecutive chemotherapy or not.) being studied.Results The median percentage volumes of bone marrow receiving 5,10,20,30,40 and 50 Gy for all patients were 98.9%, 90.5%, 80.1%, 59.4%, 38.7%, 12.2%, respectively. And the mean dose to bone marrow was 33.1 Gy. Among the total 50 patients treated with pelvic IMRT, the grade 1-4 HT of them were 21(35%), 24(40%), 3(5%), 0(0%), respectively. Among the total 107 patients treated with radiochemotherapy, there were 20(18.7%), 47(43.9%), 28(26.2%), 3(2.8%) experienced grade 1-4 HT. χ2 test showed that patients receiving radiotherapy with V10 ≥90%,V20 ≥75%,V30 ≥59.2%,V40 ≥37%, and median BM dose ≥34.1Gy had higher rates of Grade 2 HT than patients with V10 <90%,V20 <75%,V30 <59.2%,V40 <37% and median BM dose <34.1Gy(57.9% vs. 22.7%,p=0.008;52.1% vs. 16.7%,p=0.049;65.6% vs. 21.4%,p=0.001;56.3% vs. 29.6%,p=0.040;65.2% vs. 32.4%,p=0.013;respectively). Patients treated with radiochemotherapy with V10 ≥90%,V20 ≥75%,V30 ≥59.2%,V40 ≥37% also had higher rates of grade ≥2 HT(85.2% vs. 60.4%, p=0.004; 78.9% vs. 58.1%, p=0.027; 83.3% vs. 60.8%, p=0.010; 82.3% vs. 60.0%, p=0.011; respectively). No associations between HT and V5 or V50 were observed. Cancer site, age, gender, pathology, number of chemotherapy cycles, concurrent chemotherapy modality were significant predictors for acute HT. Furthermore, pelvic BM V10(P=0.008), V30(P=0.05), V40(P=0.01) were independent predictors of Grade 2 or worse HT.Conclusion V10 ≥90%, V20 ≥75%, V30 ≥59.2%, V40 ≥37% was significantly associated with increased HT during radiotherapy or chemoradiotherapy. Meanwhile, pelvic BM V10, V30, V40 could predict HT independently for cervical and rectal cancer patients who undergoing concurrent chemoradiotherapy. |
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