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“Whole brain radiotherapy: Are parotid glands organs at risk?”
Radiotherapy and Oncology 103 (2012) 130–131
Contents lists available at SciVerse ScienceDirect
Radiotherapy and Oncology journal homepage: www.thegreenjournal.com
Letter to the Editor ‘‘Whole brain radiotherapy: Are parotid glands organs at risk?’’
To the Editor In a recent analysis, Noh et al. [1] showed the dose volume statistics of the parotid glands in 32 brain metastatic patients treated with whole brain radiotherapy (WBRT total dose 30 Gy). The authors concluded that parotid glands could be regarded as organs at risk due to the high dose they received during WBRT. To investigate this aspect, we selected 30 patients with brain metastases treated by 30 Gy WBRT (3 Gy/die) and analyzed the parotid glands. Patients’ immobilization was obtained with a thermoplastic mask in supine position. One cm or 0.5 cm slice thickness Computed Tomography scans planning without intravenous contrast were performed. The Clinical Target Volume (CTV) was determinate by auto-segmentation of the brain tissue and the radiation fields included brain tissue and skull. On each scan, organs at risk were identified: left and right parotid glands were contoured and evaluated, retrospectively. Three dimensional (3D) Radiotherapy technique was optimized for each patient using the version 8.6 of Eclipse (Varian Medical System, Palo Alto, CA), with 6 MV photon beams for Varian Clinacs modeled by MLCs with 40/60 leafpairs of 10/5 (central of field) mm leaf-width. All radiotherapy plans consisted of two opposite lateral fields (gantry angles 90° and 270°); the collimator angle was chosen at about 70° to cover the entire brain tissue extension. Analysis was performed on dose–volume histogram data. The Italian Association of Radiotherapy Oncology guidelines dose constraints and the Quantec were used to evaluate the parotid glands [2,3]. Sixty parotids were contoured and evaluated. Mean parotid volumes were 20.2 cc (range 10.4–34.6) and 19.75 cc (range 9.7– 37.4); the mean parotid dose was 4.2 Gy, 3.3 Gy, and 3.3 Gy for right, left and both glands, respectively. The mean right parotid gland V10, V20, and V25 (volume that receives more than 10 Gy, Biological Effective Dose, BED = 12.5 Gy; more than 20 Gy, BED = 25 Gy and more than 25 Gy, BED = 31.25 Gy) were 11.9% (range 0–62.8%), 3.5% (range 0– 44.5%), and 1.85% (range 0–32.18%), respectively. For left parotid glands, the mean V10, V20, and V25 were 8% (range 0–66.8), 3.1 (0–44.5) and 1.8 (0–32.2), respectively. Quantec and AIRO dose constraints were respected except for 1/60 parotid gland (1.66%) that received 16.8 Gy as mean dose (BED = 21 Gy) versus 22/64 parotid glands (34.4%) reported by Noh et al. [1]. As shown in Table 1, our data are more comforting due to our different WBRT technique: our PTV included only brain
0167-8140/$ - see front matter Ó 2012 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.radonc.2012.01.013
tissue and skull, while Noh et al. included brain parenchyma, skull, and spinal cord to the lower level of the atlas; our multileaf field arrangement consisted of 2 bilateral fields (90–270°) with rotation of collimator (70° and 110°) that saves the surrounding organs at risk, while Noh et al. used 2 bilateral fields and MLC was used to spear the parotid glands. Our data showed that WBRT with opposite fields and collimator 110–70°, avoided the parotid glands. Perhaps, in patients with good prognosis treated with high technology and higher radiotherapy dose, parotid glands could be evaluated in WBRT to improve the quality of life. Funding None. Conflict of interest None. References [1] Noh OK, Chun M, Nam SS, et al. Parotid gland as a risk organ in whole brain radiotherapy. Radiother Oncol 2011;98:223–6. [2] The Italian Association Radiotherapy Oncology (AIRO) dose constraints guidelines: www.radiotherapiaitalia.it. [3] Deasy JO, Moiseenko V, Marks L, Chao KSC, Nam J, Eisbruch A. Radiotherapy dose–volume effects on salivary gland function. Int J Radiat Oncol Biol Phys 2010;76:58–63.
Alba Fiorentino Radiotherapy Oncology, IRCCS-CROB, Via Padre Pio 1, 85028, Rionero in Vulture (PZ), Italy E-mail: albafi[email protected] Costanza Chiumento Rocchina Caivano Mariella Cozzolino Stefania Clemente Piernicola Pedicini Vincenzo Fusco Radiotherapy Oncology, IRCCS-CROB, Rionero in Vulture, PZ, Italy Available online 3 March 2012
131
Letter to the Editor / Radiotherapy and Oncology 103 (2012) 130–131 Table 1 Dose statistics of parotid glands compared to Nho et al.
R Mean Min Max L Mean Min Max R–L Mean Min Max
D min (Gy) Our study
D min (Gy) Nho [1]
D max (Gy) Our study
D max (Gy) Nho [1]
Mean parotid dose (Gy) Our study
Mean parotid dose (Gy) Nho [1]
0.7 0.46 1.18
1.3 0 6.4
19.86 9.27 28.95
31 30.2 32.1
4.26 1.18 14.68
17.6 11 25.7
0.67 0.47 1.06
1.3 0.4 4.7
16.02 4.83 30.26
31 29.5 32.1
3.38 1.2 16.8
17.4 9.9 26.7
0.64 0.46 1.06
1 0 1.8
21.45 6.13 30.26
31.2 30.4 32.1
3.38 1.26 15.92
17.5 10.5 26.2
Contents lists available at SciVerse ScienceDirect
Radiotherapy and Oncology journal homepage: www.thegreenjournal.com
Letter to the Editor ‘‘Whole brain radiotherapy: Are parotid glands organs at risk?’’
To the Editor In a recent analysis, Noh et al. [1] showed the dose volume statistics of the parotid glands in 32 brain metastatic patients treated with whole brain radiotherapy (WBRT total dose 30 Gy). The authors concluded that parotid glands could be regarded as organs at risk due to the high dose they received during WBRT. To investigate this aspect, we selected 30 patients with brain metastases treated by 30 Gy WBRT (3 Gy/die) and analyzed the parotid glands. Patients’ immobilization was obtained with a thermoplastic mask in supine position. One cm or 0.5 cm slice thickness Computed Tomography scans planning without intravenous contrast were performed. The Clinical Target Volume (CTV) was determinate by auto-segmentation of the brain tissue and the radiation fields included brain tissue and skull. On each scan, organs at risk were identified: left and right parotid glands were contoured and evaluated, retrospectively. Three dimensional (3D) Radiotherapy technique was optimized for each patient using the version 8.6 of Eclipse (Varian Medical System, Palo Alto, CA), with 6 MV photon beams for Varian Clinacs modeled by MLCs with 40/60 leafpairs of 10/5 (central of field) mm leaf-width. All radiotherapy plans consisted of two opposite lateral fields (gantry angles 90° and 270°); the collimator angle was chosen at about 70° to cover the entire brain tissue extension. Analysis was performed on dose–volume histogram data. The Italian Association of Radiotherapy Oncology guidelines dose constraints and the Quantec were used to evaluate the parotid glands [2,3]. Sixty parotids were contoured and evaluated. Mean parotid volumes were 20.2 cc (range 10.4–34.6) and 19.75 cc (range 9.7– 37.4); the mean parotid dose was 4.2 Gy, 3.3 Gy, and 3.3 Gy for right, left and both glands, respectively. The mean right parotid gland V10, V20, and V25 (volume that receives more than 10 Gy, Biological Effective Dose, BED = 12.5 Gy; more than 20 Gy, BED = 25 Gy and more than 25 Gy, BED = 31.25 Gy) were 11.9% (range 0–62.8%), 3.5% (range 0– 44.5%), and 1.85% (range 0–32.18%), respectively. For left parotid glands, the mean V10, V20, and V25 were 8% (range 0–66.8), 3.1 (0–44.5) and 1.8 (0–32.2), respectively. Quantec and AIRO dose constraints were respected except for 1/60 parotid gland (1.66%) that received 16.8 Gy as mean dose (BED = 21 Gy) versus 22/64 parotid glands (34.4%) reported by Noh et al. [1]. As shown in Table 1, our data are more comforting due to our different WBRT technique: our PTV included only brain
0167-8140/$ - see front matter Ó 2012 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.radonc.2012.01.013
tissue and skull, while Noh et al. included brain parenchyma, skull, and spinal cord to the lower level of the atlas; our multileaf field arrangement consisted of 2 bilateral fields (90–270°) with rotation of collimator (70° and 110°) that saves the surrounding organs at risk, while Noh et al. used 2 bilateral fields and MLC was used to spear the parotid glands. Our data showed that WBRT with opposite fields and collimator 110–70°, avoided the parotid glands. Perhaps, in patients with good prognosis treated with high technology and higher radiotherapy dose, parotid glands could be evaluated in WBRT to improve the quality of life. Funding None. Conflict of interest None. References [1] Noh OK, Chun M, Nam SS, et al. Parotid gland as a risk organ in whole brain radiotherapy. Radiother Oncol 2011;98:223–6. [2] The Italian Association Radiotherapy Oncology (AIRO) dose constraints guidelines: www.radiotherapiaitalia.it. [3] Deasy JO, Moiseenko V, Marks L, Chao KSC, Nam J, Eisbruch A. Radiotherapy dose–volume effects on salivary gland function. Int J Radiat Oncol Biol Phys 2010;76:58–63.
Alba Fiorentino Radiotherapy Oncology, IRCCS-CROB, Via Padre Pio 1, 85028, Rionero in Vulture (PZ), Italy E-mail: albafi[email protected] Costanza Chiumento Rocchina Caivano Mariella Cozzolino Stefania Clemente Piernicola Pedicini Vincenzo Fusco Radiotherapy Oncology, IRCCS-CROB, Rionero in Vulture, PZ, Italy Available online 3 March 2012
131
Letter to the Editor / Radiotherapy and Oncology 103 (2012) 130–131 Table 1 Dose statistics of parotid glands compared to Nho et al.
R Mean Min Max L Mean Min Max R–L Mean Min Max
D min (Gy) Our study
D min (Gy) Nho [1]
D max (Gy) Our study
D max (Gy) Nho [1]
Mean parotid dose (Gy) Our study
Mean parotid dose (Gy) Nho [1]
0.7 0.46 1.18
1.3 0 6.4
19.86 9.27 28.95
31 30.2 32.1
4.26 1.18 14.68
17.6 11 25.7
0.67 0.47 1.06
1.3 0.4 4.7
16.02 4.83 30.26
31 29.5 32.1
3.38 1.2 16.8
17.4 9.9 26.7
0.64 0.46 1.06
1 0 1.8
21.45 6.13 30.26
31.2 30.4 32.1
3.38 1.26 15.92
17.5 10.5 26.2