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CASE REPORT
Year : 2020  |  Volume : 9  |  Issue : 3  |  Page : 284-286

Volumetric-modulated arc radiotherapy for pituitary macroadenoma


Department of Radiation Oncology, Government Medical College, Rajindra Hospital, Patiala, Punjab, India

Date of Submission06-May-2020
Date of Decision20-May-2020
Date of Acceptance22-May-2020
Date of Web Publication28-Jul-2020

Correspondence Address:
Dr. Anshuma Bansal
Department of Radiation Oncology, Government Medical College, Rajindra Hospital, Patiala, Punjab
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijhas.IJHAS_33_20

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  Abstract 


This case report highlights the management of nonfunctional pituitary macroadenoma with volumetric-modulated arc radiotherapy, compared to three-dimensional conformal radiotherapy.

Keywords: Pituitary macroadenoma, three-dimensional conformal radiotherapy, volumetric-modulated arc radiotherapy


How to cite this article:
Bansal A, Kaur J, Singh G, Bedi N, Kaur R, Singh RP, Dangwal V, Bagga H. Volumetric-modulated arc radiotherapy for pituitary macroadenoma. Int J Health Allied Sci 2020;9:284-6

How to cite this URL:
Bansal A, Kaur J, Singh G, Bedi N, Kaur R, Singh RP, Dangwal V, Bagga H. Volumetric-modulated arc radiotherapy for pituitary macroadenoma. Int J Health Allied Sci [serial online] 2020 [cited 2020 Sep 23];9:284-6. Available from: http://www.ijhas.in/text.asp?2020/9/3/284/290718




  Introduction Top


Pituitary macroadenomas are usually treated with radiotherapy in postoperative settings. The major concern is to deliver lesser possible doses to the temporal lobes to decrease neurocognitive disorders.[1] This case report signifies the importance of delivering radiation by advanced volumetric-modulated arc radiotherapy (VMAT) planning technique compared to three-dimensional conformal radiotherapy (3DCRT) planning.


  Case Report Top


A 32-year-old female patient presented in October 2019 with progressive diminution in vision in bilateral eyes (right more than left) and headache for the past 2 months. CEMRI (contrast-enhanced magnetic resonance imaging) performed on September 26, 2019, showed a 3.5 cm × 3.0 cm × 2.7 cm space-occupying lesion with intense postcontrast enhancement in the sellar and suprasellar region with nonvisualized separate pituitary gland. Inferiorly, it was bulging into the sphenoid sinus and superiorly it was compressing optic chiasma. On the left side, the mass was bulging into the left cavernous sinus partially encasing the left internal carotid artery. Anterosuperiorly, it was abutting basifrontal lobes and anterior aspect of the third ventricle [Figure 1].
Figure 1: Preoperative CEMRI of the brain

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Her baseline hormone profile (serum cortisol, IGF-1, T3, T4, and TSH levels) was normal.

The patient underwent endoscopic transsphenoidal subtotal excision of the tumor on 22.10.19. The histopathology report was suggestive of pituitary adenoma.

Postoperative contrast enhanced magnetic resonance imaging (CEMRI) done on 19.12.19 showed deformed sellar with a well-defined lesion 2.4 cm × 2.2 cm × 1.6 cm in the superior part of the sellar and suprasellar region bulging into the inferior part of the third ventricle [Figure 2].
Figure 2: Postoperative CEMRI of the brain

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Postoperative serum cortisol levels were mildly raised, and the patient was started with tablet hydrocortisone 5 mg thrice a day.

The patient was simulated using facial thermoplastic masks as immobilizers and VMAT plan was elaborated with Varian External beam planning system version 13.7. Dose delivered was 54 Gy in 27 fractions in 5.5 weeks, prescribed to the 95% isodose line covering the planning target volume (PTV), with two semiarcs (250° clockwise 120° coplanar arc and 160° counterclockwise 40° noncoplanar arc) with 6 MV beams on the varian truebeam linear accelerator [Figure 3].
Figure 3: Volumetric-modulated arc radiotherapy planning for treatment

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Normal tissue dose constraints were achieved, with Dmax of 54 Gy to the brainstem, optic chiasma and bilateral optic nerves, Dmax to bilateral lens of <7 Gy, mean dose to bilateral eyes of <35 Gy, Dmax temporal lobes of <54 Gy, and Dmean to parotids of <3 Gy. Cone-beam computed tomography was done every day before treatment for image guidance and precise treatment delivery to the target lesion.

The patient is now on regular follow-up and is doing well.


  Discussion Top


Pituitary adenomas account for <10%–15% of primary intracranial tumors and nonfunctioning pituitary adenomas account for 50% of all pituitary macroadenomas.[2] Pituitary macroadenomas are benign tumors >10 mm, growing superiorly out of the pituitary fossa, affecting the central part of the chiasm by contacting, elevating, and compressing it, leading to classical bitemporal hemianopia in most individuals.

With the advancement in radiotherapy technology, pituitary tumors are now being treated with radiation techniques which achieve good coverage to target regions and minimal possible doses to nearby critical organs such as the optic nerves, optic chiasma, brainstem, lens, and eyes.[3]

3DCRT is still the standard approach for these patients as dose constraints to normal structures are achieved most of the times.[4] However, the highly advanced VMAT planning has a role to play when the tumors are very close/abutting the critical structures and also when the aim is to deliver the least possible doses to all normal structures. In our patient, the mean doses to PTV were 55.95 and 55.35 by VMAT [Figure 3] and 3DCRT [Figure 4], which shows that PTV coverage was not compromised by the planning technique. However, as is evident from [Table 1], VMAT planning is superior to the 3DCRT plan when doses to organs at risk were compared.
Figure 4: Three-dimensional conformal radiotherapy plan for comparison

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Table 1: Doses received by organs at risk when treated with volumetric-modulated arc radiotherapy compared to three-dimensional conformal radiotherapy plan

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A comparison study in pituitary adenoma by Arauz et al.[5] has shown that VMAT compared to 3DCRT achieves lesser brainstem V20 Gy (32.5% and 78%) and lesser temporal lobes V25 Gy (15.5% and 62.5%). Hence, they recommend making the comparative dosimetric analysis between VMAT and 3DCRT before choosing the best plan.

Parhar et al.[6] studied 15 such patients and found similar results as above when compared temporal lobes V25 Gy received by intensity-modulated radiotherapy (IMRT) and 3DCRT plans and concluded that IMRT may help preventing neurocognitive sequelae in irradiated pituitary macroadenoma patients.

The only limitation of VMAT planning is the higher integral doses to normal body minus PTV tumor when compared to 3DCRT plans. In our patient, the mean integral dose was 169 cGy by 3DCRT plans and 188 cGY by VMAT. When integral doses to 10% of normal body minus PTV were compared, it was 1.54 Gy by 3DCRT and 5.26 Gy by VMAT. In long terms, this can lead to a higher risk of developing second malignancy when planned by VMAT.[7]


  Conclusion Top


VMAT plans can be optimally utilized in selective cases of pituitary tumors where the target lies very close to critical structure such as optic chiasma and optic nerve, or in cases of re-irradiation, when minimal possible doses need to be delivered to organs at risk.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Monje ML, Palmer T. Radiation injury and neurogenesis. Curr Opin Neurol 2003;16:129-34.  Back to cited text no. 1
    
2.
Melmed S. Mechanisms for pituitary tumorigenesis: The plastic pituitary. J Clin Invest 2003;112:1603-18.  Back to cited text no. 2
    
3.
Grabenbauer GG, Ernst-Stecken A, Schneider F, Lambrecht U, Ganslandt O. Radiosurgery of functioning pituitary adenomas: Comparison of different treatment techniques including dynamic and conformal arcs, shaped beams, and IMRT. Int J Radiat Oncol Biol Phys 2006;66:S33-9.  Back to cited text no. 3
    
4.
Ahmad M, Fontenla DP, Lai PP, Rowe JD, Yaparpalvi R, Deore SM, et al. Three-dimensional external-beam radiation treatment planning and real-time dose verification of pituitary adenoma: Clinical and physical considerations. Radiat Oncol Invest 1995;3:141-8.  Back to cited text no. 4
    
5.
Arauz R, Rodriguez M. RT-02: Comparison of 3DCRT, IMRT AND VMAT for postsurgery radiotherapy for pituitary macroadenomas. Neuro Oncol 2014;16 (Suppl 5):v188.  Back to cited text no. 5
    
6.
Parhar PK, Duckworth T, Shah P, DeWyngaert JK, Narayana A, Formenti SC, et al. Decreasing temporal lobe dose with five-field intensity-modulated radiotherapy for treatment of pituitary macroadenomas. Int J Radiat Oncol Biol Phys 2010;78:379-84.  Back to cited text no. 6
    
7.
Sakthivel V, Kadirampatti Mani G, Mani S, Boopathy R, Selvaraj J. Estimating second malignancy risk in intensity-modulated radiotherapy and volumetric-modulated arc therapy using a mechanistic radiobiological model in radiotherapy for carcinoma of left breast. J Med Phys 2017;42:234-40.  Back to cited text no. 7
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