Technique for sparing previously irradiated critical normal structures in salvage proton craniospinal irradiation

Radiation Oncology

Jeffrey C Buchsbaum¹  Joseph W Simmons¹  Mark R Wolanski¹  Mark W McDonald¹ 

[1] Indiana University Health Proton Therapy Center, Bloomington, IN, USA

关键词: Treatment planning;    Reirradiation;    Craniospinal irradiation;    Proton therapy;   

Others  :  1154734
DOI  :  10.1186/1748-717X-8-14

 received in 2012-07-17, accepted in 2012-12-27,  发布年份 2013

【 摘 要 】

Background

Cranial reirradiation is clinically appropriate in some cases but cumulative radiation dose to critical normal structures remains a practical concern. The authors developed a simple technique in 3D conformal proton craniospinal irradiation (CSI) to block organs at risk (OAR) while minimizing underdosing of adjacent target brain tissue.

Methods

Two clinical cases illustrate the use of proton therapy to provide salvage CSI when a previously irradiated OAR required sparing from additional radiation dose. The prior radiation plan was coregistered to the treatment planning CT to create a planning organ at risk volume (PRV) around the OAR. Right and left lateral cranial whole brain proton apertures were created with a small block over the PRV. Then right and left lateral “inverse apertures” were generated, creating an aperture opening in the shape of the area previously blocked and blocking the area previously open. The inverse aperture opening was made one millimeter smaller than the original block to minimize the risk of dose overlap. The inverse apertures were used to irradiate the target volume lateral to the PRV, selecting a proton beam range to abut the 50% isodose line against either lateral edge of the PRV. Together, the 4 cranial proton fields created a region of complete dose avoidance around the OAR. Comparative photon treatment plans were generated with opposed lateral X-ray fields with custom blocks and coplanar intensity modulated radiation therapy optimized to avoid the PRV. Cumulative dose volume histograms were evaluated.

Results

Treatment plans were developed and successfully implemented to provide sparing of previously irradiated critical normal structures while treating target brain lateral to these structures. The absence of dose overlapping during irradiation through the inverse apertures was confirmed by film. Compared to the lateral X-ray and IMRT treatment plans, the proton CSI technique improved coverage of target brain tissue while providing the least additional radiation dose to the previously irradiated OAR.

Conclusions

Proton craniospinal irradiation can be adapted to provide complete sparing of previously irradiated OARs. This technique may extend the option of reirradiation to patients otherwise deemed ineligible for further radiotherapy due to prior dose to critical normal structures.

【 授权许可】

   
2013 McDonald et al.; licensee BioMed Central Ltd.

【 图 表 】

Figure 1.

Figure 2.

Figure 3.

Figure 4.

Figure 5.

Figure 6.

Figure 7.

Figure 8.

Figure 9.

【 参考文献 】

• [1]Merchant TE, Boop FA, Kun LE, Sanford RA: A retrospective study of surgery and reirradiation for recurrent ependymoma. Int J Radiat Oncol Biol Phys 2008, 71:87-97.
• [2]Massimino M, Gandola L, Spreafco F, Biassoni V, Luksch R, Collini P, Solero CN, Simonetti F, Pignoli E, Cefalo G, Poggi G, Modena P, Mariani L, Potepan P, Podda M, Casanova M, Pecori E, Acerno S, Ferrari A, Terenziani M, Meazza C, Polastri D, Ravagnani F, Fossati-Bellani F: No salvage using high-dose chemotherapy plus/minus reirradiation for relapsing previously irradiated medulloblastoma. Int J Radiat Oncol Biol Phys 2009, 73:1358-1363.
• [3]Wei RL, Nguyen ST, Yang JN, Wolff J, Mahajan A: Salvage craniospinal irradiation with an intensity modulated radiotherapy technique for patients with disseminated neuraxis disease. Practical Radiat Oncol 2012, 2:e69-e75.
• [4]McDonald MW, Fitzek MM: Proton Therapy. Curr Probl Cancer 2010, 34:251-296.
• [5]Buchsbaum JC, Besemer A, Simmons J, et al.: Supine proton beam craniospinal radiotherapy using a novel tabletop adapter. Med Dosimavailable online 28 August 2012, epub ahead of print, available online at http://dx.doi.org/10.1016/j.meddos.2012.07.003 webcite
• [6]Nieder C, Milas L, Ang KK: Tissue tolerance to reirradiation. Semin Radiat Oncol 2000, 10:200-209.
• [7]Mayer R, Sminia P: Reirradiation tolerance of the human brain. Int J Radiat Oncol Biol Phys 2008, 70:1350-1360.
• [8]Koot RW, Stalpers LJA, Aronica E, Andries Bosch D: Cerebral necrosis after 25 Gy radiotherapy in childhood followed 28 years later by 54 Gy radiotherapy. Clin Neurol Neurosurg 2007, 109:607-612.
• [9]Gondi V, Tolakanahalli R, Mehta MP, Tewatia D, Rowley H, Kuo JS, Khuntia D, Tomé WA: Hippocampal-sparing whole-brain radiotherapy: a "how-to" technique using helical tomotherapy and linear accelerator-based intensity-modulated radiotherapy. Int J Radiat Oncol Biol Phys 2010, 78:1244-1252.
• [10]Yoon M, Shin DH, Kim J, Kim JW, Kim DW, Park SY, Lee SB, Kim JY, Park HJ, Park BK, Shin SH: Craniospinal irradiation techniques: a dosimetric comparison of proton beams with standard and advanced photon radiotherapy. Int J Radiat Oncol Biol Phys 2011, 81:637-646.
• [11]Yuh GE, Loredo LN, Yonemoto LT, Bush DA, Shahnazi K, Preston W, Slater JM, Slater JD: Reducing toxicity from craniospinal irradiation: using proton beams to treat medulloblastoma in young children. Cancer J 2004, 10:386-390.
• [12]Bednarz B, Daartz J, Paganetti H: Dosimetric accuracy of planning and delivering small proton therapy fields. Phys Med Biol 2010, 55:7425-7438.