ABSTRACT
Objective To investigate the correlation between dose volume histogram(DVH)of tumor targets and organs at risk(OAR)at CT-image based 192Ir brachytherapy and effects and complications for patients with locally advanced cervical cancer. Methods Ten patients with FIGO stage ⅢB cervical cancer received CT image-based 192Ir intracavitary brachytherapy after 54 Gy of three-dimentional four-field pelvic external beam radiotherapy and concurrent weekly cisplatin chemotherapy. Before each brachytherapy,CT images were acquired with applicators in place. Gross tumor volume(GTV), clinical target volume (CTV)and OAR were contoured and inverse treatment planning was designed and optimized by using PLATO treatment planning system. Conventional two-dimensional plans were also designed for comparison.The total intracavitary brachytherapy dose was 30 -42 Gy in 5 -7 fractions. The patients were followed, and the local control and complications were analyzed. The biologically equivalent dose(BED)and biologically equivalent dose in 2 Gy fractions(BED2)for GTV, CTV and OAR were calculated. The minimum dose in the most irradiated tissue volume 2 cm3(D2 cm3)adjacent to the applicator of the sigmoid colon, rectum,bladder and small bowel was determined from the DVH. Results The 1-year local pelvic control rate was 90% and grade 1-2 late complication of sigmoid colon and rectum was 50%. No grade 3 or more complications developed. On CT-image based planning, the BED and BED2 to 90% of the CTV(D90)were 95.50 Gy ± 7. 81 Gy and 79. 73 Gy ± 6. 57 Gy. The BED and BED2 to 90% of the GTV(D90)were 101.86 Gy ± 7.27 Gy and 84. 95 Gy ± 6. 1 Gy. The volume enclosed by 90% of prescribed dose(V90)for GTV and CTV were 92% ±4% and 87% ±7% respectively. The D2cm3 for rectum and sigmoid colon were 74. 97 Gy ±1.64 Gy and 67. 93 Gy ± 4. 30 Gy(EQD2, α/β = 3). Comparing with 2D brachytherapy plans , CT - image based planning has improved D90 and V90 for GTV and CTV with similar dose at point A and rectum reference point. Conclusions Computer tomography-image based 192Ir brachytherapy has resulted in the better dose distribution to the tumor targets with excellent tumor control and acceptable toxicity.
ABSTRACT
PURPOSE: This study was designed to assess the incidence of pulmonary toxicity (PT) and related risk factors in breast cancer patients treated with postoperative adjuvant radiotherapy (RT) with or without the use of chemotherapy. METHODS: The whole breast or chest wall was irradiated with two tangential photon fields to a total dose of 50.4 Gy in 261 patients. A single anterior oblique photon field for a supraclavicular (SCL) node included if indicated. All patients underwent three-dimensional RT planning (3D RTP), and the calculation of dose volume histogram (DVH) parameters (i.e., ipsilateral lung volume that received > or =15 Gy [V15], V20, V30, and mean lung dose [MLD]). The relationship of symptomatic radiation pneumonitis (SRP) and pulmonary toxicity as discerned by radiographic features (radiographic pulmonary toxicity or RPT) with the clinical and DVH parameters were evaluated. In addition, the relationship of severity of RPT with the DVH parameters was assessed. RESULTS: SRP and RPT developed in 1.9% (5/261) and 22.6% (59/261) of patients, respectively. Age (p=0.008), inclusion of an SCL field (p<0.0001), use of chemotherapy (p<0.0001), use of taxane (p<0.0001), and all DVH parameters (p<0.0001) were associated with RPT in univariate analysis. Based on the results of multivariate analysis, V30 (p<0.001), age (p=0.001) and use of taxane (p=0.036) were significant risk factors in the development of RPT. None of the DVH parameters was associated with the severity of RPT. CONCLUSION: The incidence rate of SRP was very low and there was no correlation between any clinical factor or DVH parameters and SRP. Age, the use of taxane-based chemotherapy and V30 were correlated with the development of RPT.