New Clinical Features and Dosimetric Predictor Identification for Symptomatic Radiation Pneumonitis after Tangential Irradiation in Breast Cancer Patients.

Background: Tangential irradiation is the most popular postoperative radiotherapy technique for breast cancer. However, irradiation has been related to symptomatic radiation pneumonitis (SRP), which decreases the quality of life of patients. This study investigated the clinical features and dosimetric parameters related to SRP of the ipsilateral lung to identify risk factors for SRP in breast cancer patients after three-dimensional conformal radiation therapy (3D-CRT) with tangential fields. Material and Methods: A total of 515 breast cancer patients were evaluated and divided into two groups: the local-regional irradiation group (259 patients) and the simple local irradiation group (256 patients). Clinical symptoms were registered and patient data collected. The relationship between the incidence of SRP and dosimetric parameters for the ipsilateral lung was assessed within 6 months after 3D-CRT. Dosimetric parameters were compared using t tests. The dosimetric predictors for SRP were estimated using a logistic regression model and receiver operating characteristic curve analysis. Results: In total, 19 patients (3.7%) developed grade 2 SRP. In the local-regional irradiation group, the probability of SRP in the lung body was greater than that in the lung apex (3.9% vs. 1.5%). V20 and V30 were independent predictors for SRP in the local-regional irradiation group (odds ratio = 1.152 and 1.439, both p = 0.030), whereas only V20 was an independent predictor of SRP in the simple local irradiation group (odds ratio = 1.351, p = 0.001). With 39.8% as the optimal threshold for V20 and 25.7% for V30 for local-regional irradiation, SRP could be predicted with an accuracy of 80.3% and 79.9%, a sensitivity of 61.5% and 69.2%, and a specificity of 81.3% and 80.5%, respectively. With 20.2% as the optimal V20 threshold for simple local irradiation, SRP could be predicted with an accuracy of 88.7%, a sensitivity of 83.3% and a specificity of 89.6%. Conclusions: SRP has become a rare complication with mild symptoms and occurs mainly in the lung body. V20 and V30 may be useful dosimetric predictors to evaluate SRP risk of the ipsilateral lung in breast cancer.

[Primary exploration of individual biological boosting target volume for locally advanced nasopharyngeal carcinoma].

OBJECTIVE: To explore the methods of detecting and defining the biological boosting target volume (BBTV) in patients with locally advanced nasopharyngeal carcinoma (NPC). METHODS: Ten patients with locally advanced NPC treated at our center during September to December 2010 were enrolled. The following factors were used to define and contour BBTV, including dose-deficient area locating at skull-base of gross tumor volume in conventional irradiation, hypoxia area detected by (99m)Tc-HL91 Single-photon emission computed tomography/computed tomography (SPET/CT) imaging and tumor-burdened area evaluated by comparing the pre-treatment and 36 Gy irradiation's CT images scanning at the same treatment position. RESULTS: The volume of BBTV was (17 ± 7) cm(3), accounting for 51% ± 19% of gross tumor volume. In BBTV, the volumes and proportion of skull base dose-deficient, hypoxia and tumor-burdened area were (5.8 ± 2.5) cm(3), (7.7 ± 3.6) cm(3), (9.0 ± 5.8) cm(3) and 34.4%, 45.7% and 53.3% respectively. However, the proportion of overlapping volume between three areas was only 33.1%. CONCLUSION: BBTV may be composed of skull base dose-deficient, hypoxia and tumor-burdened volume. It provides a new reference for individualized radiotherapy in locally advanced NPC.

In vivo verification of superficial dose for head and neck treatments using intensity-modulated techniques.

Skin dose is one of the key issues for clinical dosimetry in radiation therapy. Currently planning computer systems are unable to accurately predict dose in the buildup region, leaving ambiguity as to the dose levels actually received by the patient's skin during radiotherapy. This is one of the prime reasons why in vivo measurements are necessary to estimate the dose in the buildup region. A newly developed metal-oxide-semiconductor-field-effect-transistor (MOSFET) detector designed specifically for dose measurements in rapidly changing dose gradients was introduced for accurate in vivo skin dosimetry. The feasibility of this detector for skin dose measurements was verified in comparison with plane parallel ionization chamber and radiochromic films. The accuracy of a commercial treatment planning system (TPS) in skin dose calculations for intensity-modulated radiation therapy treatment of nasopharyngeal carcinoma was evaluated using MOSFET detectors in an anthropomorphic phantom as well as on the patients. Results show that this newly developed MOSFET detector can provide a minimal but highly reproducible intrinsic buildup of 7 mg cm(-2) corresponding to the requirements of personal surface dose equivalent Hp (0.07). The reproducibility of the MOSFET response, in high sensitivity mode, is found to be better than 2% at the phantom surface for the doses normally delivered to the patients. The MOSFET detector agrees well with the Attix chamber and the EBT Gafchromic film in terms of surface and buildup region dose measurements, even for oblique incident beams. While the dose difference between MOSFET measurements and TPS calculations is within measurement uncertainty for the depths equal to or greater than 0.5 cm, an overestimation of up to 8.5% was found for the surface dose calculations in the anthropomorphic phantom study. In vivo skin dose measurements reveal that the dose difference between the MOSFET results and the TPS calculations was on average -7.2%, ranging from -4.3% to -9.2%. The newly designed MOSFET detector encapsulated into a thin water protective film has a minimal reproducible intrinsic buildup recommended for skin dosimetry. This feature makes it very suitable for routine IMRT QA and accurate in vivo skin dosimetry.

[A matched cohort analysis of three-dimensional conformal radiotherapy versus conventional radiotherapy for primary nasopharyngeal carcinoma].

BACKGROUND & OBJECTIVE: Comparing with two-dimensional conventional radiotherapy (2D CRT), three-dimensional conformal radiotherapy (3D CRT) features a precise tumor target volume positioning and a three-dimensional display of the tumor and surrounding normal tissues, therefore, helps to spare normal tissues in the radiotherapy for nasopharyngeal carcinoma (NPC). This study was to explore whether 3D CRT can increase the locoregional control rate while reduce the occurrence and severity of radiation-related sequelae for primary NPC patients. METHODS: Clinical data of 95 primary NPC patients, treated by 3D CRT from Feb. 2001 to Apr. 2004, were reviewed. These patients were then compared with a cohort of 95 NPC patients treated by 2D CRT from Jan. 2002 to Dec. 2003, who were matched in respect of 92 Fuzhou stage, T stage, N stage, sex and age. The short-term and long-term outcomes and radiation-related sequelae of the two groups were compared. RESULTS: There was no significant differences in the 5-year locoregional control rate (89.7% vs. 90.6%, P=0.783), local control rate (91.8% vs. 92.8%, P=0.758), regional control rate (95.6% vs. 97.8%, P=0.427), and distant metastasis-free survival rate (93.1% vs. 86.4%, P=0.152) between 3D CRT group and 2D CRT group. The 5-year overall and progression-free survival rates were slightly higher in 3D CRT group than in 2D CRT group (91.9% vs. 82.0%, P=0.072; 85.7% vs. 71.0%, P=0.087). Eighty-one patients in 3D CRT group and 70 patients in 2D CRT group who had survived without disease progression were compared in respect of late radiation-related sequelae. The occurrence rates of moderate or severe xerostomia and trismus were significantly lower in 3D CRT group than in 2D CRT group (37.0% vs. 71.4%, P<0.001; 6.2% vs. 28.6%, P<0.001). But there were no differences in functional impairment of hearing, memory and injury of cranial nerves between these two groups. CONCLUSION: Comparing with 2D CRT, 3D CRT can reduce the occurrence of late radiation-related sequelae, such as xerostomia and trismus, for primary NPC, and it is likely to prolong overall and progression-free survival.

[Dosimetric analysis of radiotherapy with middle shielding blocks of different widths at the lower cervical supraclavicular field for stage N2-3 nasopharyngeal carcinoma].

BACKGROUND & OBJECTIVE: Anterior tangential field irradiation with middle shielding block at the lower cervical and supraclavicular region is needed in the conventional radiotherapy for stage N2-3 nasopharyngeal carcinoma (NPC), but there are still some disagreements on block width. This study was to explore a reasonable block width by dosimetric analysis of anterior tangential field irradiation with middle shielding blocks of different widths designed by the 3-dimensional treatment planning system (3D-TPS) at the lower cervical supraclavicular region for stage N2-3 NPC. METHODS: Ten untreated patients with stage N2-3 NPC received 3D-TPS-designed irradiation plan. For every patient, a gradual shrinking field technique was adopted. Single anterior tangential fields were set at the lower cervical and supraclavicular region and irradiated with middle shielding blocks of different widths: 0 cm (Plan A), 2.1 cm (Plan B), 2.5 cm (Plan C), and 3 cm (Plan D) for the first 40 Gy, then 3 cm for residual dose for all 4 plans. The prescribed doses were the same for 4 plans for every patient. The irradiated volumes and doses of target volumes and organs at risk among the 4 plans were compared. RESULTS: The high dose coverage (V95 and V90) of plan target volume (PTV) for the subclinical lesion region at the lower cervical supraclavicular region (PTV50a) was significantly higher in Plan A than in Plans B, C, and D (82.44% vs. 78.21%, 77.10% and 73.80% for V95, 87.89% vs. 84.03%, 82.68% and 77.50% for V90, P<0.05), and significantly higher in Plans B and C than in Plan D (P<0.05), but there was no difference between Plans B and C (P>0.05). There was no significant difference in high dose coverage (V95 and V90) of PTV for the primary gross tumor region (PTVnx), PTV for the cervical metastatic nodes (PTVnd), PTV for the high risk region around primary gross tumor (PTVnx60), PTV for the high risk region around metastatic nodes (PTVnd60), and subclinical lesion region above cricoid cartilage (PTV50b) among the 4 plans. There was no difference in the doses for the spinal cord and larynx among the 4 plans. The maximal doses for 50% volumes of target organs (D50) were significantly higher in Plan A than in Plans B, C, and D (49.47 Gy vs. 41.95 Gy, 38.73 Gy, and 26.82 Gy for the thyroid gland, 44.52 Gy vs. 8.41 Gy, 7.03 Gy, and 5.63 Gy for the esophagus, 44.18 Gy vs. 10.16 Gy, 8.55 Gy, and 7.60 Gy for the trachea, P<0.05), and higher in Plans B and C than in Plan D (P<0.05), but there was no difference between Plans B and C (P>0.05). The normal tissue complication probability (NTCP) of the thyroid gland was significantly higher in Plan A than in Plans B, C, and D (7.9% vs. 4.8%, 4.3%, and 3.0%, P<0.05), and higher in Plans B and C than in Plan D, but there was no difference between Plans B and C (P>0.05). There were no difference in the doses for the spinal cord and larynx among the 4 plans. The maximal doses for 50% volumes of target organs (D50) were significantly higher in Plan A than in Plans B, C, and D (49.47 Gy vs. 41.95 Gy, 38.73 Gy, and 26.82 Gy for the thyroid gland, 44.52 Gy vs. 8.41 Gy, 7.03 Gy, and 5.63 Gy for the esophagus, 44.18 Gy vs. 10.16 Gy, 8.55 Gy, and 7.60 Gy for the trachea, P<0.05), and higher in Plans B and C than in Plan D (P<0.05), but there was no difference between Plans B and C (P>0.05). The normal tissue complication probability (NTCP) of the thyroid gland was significantly higher in Plan A than in Plans B, C, and D (7.9% vs. 4.8%, 4.3%, and 3.0%, P<0.05), and higher in Plans B and C than in Plan D, but there was no difference between Plans B and C (P>0.05). There were no difference in the NTCP of other organs at risk among the 4 plans (P>0.05). CONCLUSIONS: Not obviously increasing the irradiation doses for critical organs at risk, Plan A has the best high dose coverage at the subclinical lesion region of the lower cervical and supraclavicular region, while Plan D the worst. We recommend to use no middle shielding block in the anterior tangential field for the first 40 Gy, then use individual middle shielding blocks of 2.1-2.5 cm in the institutes at where set up error is small.

[Three-dimensional conformal radiotherapy for primary nasopharyngeal carcinoma and analysis of locoregional recurrence].

BACKGROUND & OBJECTIVE: The efficacy of routine two-dimensional radiotherapy for primary nasopharyngeal carcinoma (NPC) is dissatisfied, while three-dimensional conformal radiotherapy (3-D CRT) can optimize irradiation dose distribution. This study was to explore the efficacy of 3-D CRT on NPC, and investigate dosimetric factors of locoregional failure. METHODS: Records of 87 patients with primary NPC, treated with 3-D CRT between Feb. 2001 and Apr. 2004, were retrospectively reviewed. Dosimetric analysis was performed on the patients with locoregional relapse. RESULTS: Of the 87 patients, 5 (5.7%) had local failure, and 2 (2.3%) had regional failure. The overall 3-year locoregional control rate was 90.2%. The 3-year local control rates for stages T1, T2, T3, and T4 patients were 95.0%, 97.0%, 80.1%, and 100%, respectively. Five cases (71%) were marginal or outside failures of the irradiation fields. The occurrence rate of grade 3-4 late complications of the 62 patients progress-freely survived over 12 months was 9.7%. The 3-year overall survival rate and progress-freely survival rate were 88.2% and 80.3%, respectively. The 3-year survival rates were significantly higher in the patients at stages I, II, and III ('92 Fuzhou staging) than in the patients at stage IVa (100%, 100%, 84.7% vs. 47.5%, P<0.001). CONCLUSIONS: Increased locoregional control rate and reduced occurrence of grade 3-4 late complications of primary NPC could be achieved by 3-D CRT through careful delineation of target volumes and design of irradiation fields. Missing of target volumes is a reason of local relapse.