{"id":14303,"date":"2026-03-12T07:39:00","date_gmt":"2026-03-12T10:39:00","guid":{"rendered":"https:\/\/rtmedical.com.br\/tmp-en-1773311935645\/"},"modified":"2026-04-04T18:08:17","modified_gmt":"2026-04-04T21:08:17","slug":"benign-cns-tumors-delineation","status":"publish","type":"post","link":"https:\/\/rtmedical.com.br\/en\/benign-cns-tumors-delineation\/","title":{"rendered":"Benign CNS Tumors: Target Delineation &#038; RT"},"content":{"rendered":"<h2>Benign CNS tumors and the role of radiotherapy<\/h2>\n<p>Benign tumors of the central nervous system \u2014 meningiomas, vestibular schwannomas, pituitary adenomas, and glomus tumors \u2014 form a diverse group of lesions that, despite their benign histology, often demand precise radiotherapy. Accurate target volume delineation and appropriate technique selection are what drive long-term local control and functional preservation.<\/p>\n<p>Patient workup starts with a thorough neurologic history, focused physical examination, hormonal panels, visual field and acuity testing, audiometry, and baseline neurocognitive assessment. Maximal safe surgical resection \u2014 ideally gross total resection \u2014 remains the standard of care for operable, surgically accessible tumors. Multidisciplinary management is strongly recommended across all subtypes. When surgery is not feasible or complete, definitive radiation therapy becomes the primary treatment modality. This article details the contouring rationale, dose prescriptions, fractionation schedules, and planning strategies for each subtype, based on our <a href=\"#\">complete guide on target volume delineation<\/a>.<\/p>\n<h2>Patient positioning, immobilization, and simulation<\/h2>\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" class=\"alignright lazyload\" data-src=\"https:\/\/rtmedical.com.br\/wp-content\/uploads\/2026\/04\/benign-cns-oar-brain-window.jpeg\" alt=\"Axial CT simulation slices in brain window showing delineated organs at risk for primary brain tumors, including brainstem, optic chiasm, and hippocampus\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 690px; --smush-placeholder-aspect-ratio: 690\/788;\"><figcaption>Figure 29.1 \u2014 OARs in brain window. Source: Target Volume Delineation and Field Setup, 2nd Edition<\/figcaption><\/figure>\n<p>Patients are simulated supine with arms parallel to the body and shoulders in a natural position. Standard immobilization uses an indexed 3-point thermoplastic mask. For skull base tumors or lesions near the optic apparatus, a 5-point mask reinforces neck positioning. MRI-simulated patients use a clamshell mask. Head and chin rest in a neutral position unless base-of-skull positioning demands otherwise.<\/p>\n<p>Axial CT images are acquired at 1 mm slice thickness for SRS, FSRT, and proton beam therapy, or 2 mm for 3D-CRT, IMRT, and VMAT, covering the entire head down to the shoulders. Co-registration with diagnostic MRI is strongly recommended \u2014 T1 post-contrast or FLAIR sequences for tumor visualization, and native T1 or 3D T2\/CISS sequences for cranial nerve and hippocampal delineation. IV contrast is used unless medically contraindicated.<\/p>\n<h2>Organs-at-risk delineation<\/h2>\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" class=\"alignleft lazyload\" data-src=\"https:\/\/rtmedical.com.br\/wp-content\/uploads\/2026\/04\/benign-cns-oar-soft-tissue.jpeg\" alt=\"CT simulation slices in soft tissue window demonstrating optic nerves traversing the optic canals and orbital components as organs at risk\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 690px; --smush-placeholder-aspect-ratio: 690\/788;\"><figcaption>Figure 29.2 \ufffd\ufffd OARs in soft tissue window. Source: Target Volume Delineation and Field Setup, 2nd Edition<\/figcaption><\/figure>\n<p>The list of normal structures to contour is extensive. For most benign primary brain tumors, OARs include: whole brain, uninvolved brain (brain minus GTV or CTV depending on the scenario), brainstem divided into core and surface (typically a 3 mm peripheral rind), spinal cord, bilateral cochleae, globes, lenses, optic nerves, optic chiasm, retinas, lacrimal glands, temporal lobes, hippocampi, hypothalamus, and pituitary gland. Planning risk volumes (PRVs) can be created for tumors abutting critical structures to aid dosimetric evaluation.<\/p>\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" class=\"alignright lazyload\" data-src=\"https:\/\/rtmedical.com.br\/wp-content\/uploads\/2026\/04\/benign-cns-cochlea-bone-window-1.jpeg\" alt=\"CT simulation in bone window demonstrating bilateral cochleae identification and delineation for brain tumor planning\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 690px; --smush-placeholder-aspect-ratio: 690\/787;\"><figcaption>Figure 29.3 \u2014 Cochleae in bone window. Source: Target Volume Delineation and Field Setup, 2nd Edition<\/figcaption><\/figure>\n<p>Each OAR has an optimal viewing window. The brainstem, optic chiasm, and intracranial optic nerves are best seen in brain window. Optic nerves within the optic canals and their orbital components are clearer in soft tissue window. Cochleae are only accurately identified in bone window \u2014 and depending on head position, they may not appear on the same axial slice. The hippocampus \u2014 specifically the subgranular zone \u2014 is delineated on T1 MRI and visualized as hypointense gray matter, from the level where it borders the lateral ventricle atrium superiorly down to the inferior extent of the temporal horn.<\/p>\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" class=\"alignleft lazyload\" data-src=\"https:\/\/rtmedical.com.br\/wp-content\/uploads\/2026\/04\/benign-cns-hippocampus-delineation-1.jpeg\" alt=\"CT simulation and T1 post-contrast MRI used for hippocampal delineation showing right and left hippocampus for treatment planning\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 505px; --smush-placeholder-aspect-ratio: 505\/905;\"><figcaption>Figure 29.4 \u2014 Hippocampal delineation on CT and MRI. Source: Target Volume Delineation and Field Setup, 2nd Edition<\/figcaption><\/figure>\n<h2>Low-grade astrocytic and oligodendroglial tumors<\/h2>\n<p>Patients with low-grade diffuse astrocytomas (IDH-mutated) and oligodendrogliomas undergo maximal safe resection for diagnosis and molecular characterization. Standard radiotherapy delivers 54 Gy in 30 fractions with conventionally fractionated technique. Chemotherapy is recommended for grade 2 or higher tumors harboring certain high-risk features. IDH wild-type tumors receive multimodality treatment analogous to malignant gliomas, reflecting their unfavorable natural history.<\/p>\n<p>SRS is not recommended for these tumors in the upfront setting, except for select pilocytic astrocytoma cases.<\/p>\n<h3>Target volumes for astrocytic and oligodendroglial tumors<\/h3>\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" class=\"alignright lazyload\" data-src=\"https:\/\/rtmedical.com.br\/wp-content\/uploads\/2026\/04\/benign-cns-oligodendroglioma-planning-1.jpeg\" alt=\"Treatment planning CT and post-contrast FLAIR MRI for oligodendroglioma after left frontotemporoparietal craniotomy with GTV in red, CTV in yellow, and PTV in blue\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 457px; --smush-placeholder-aspect-ratio: 457\/1116;\"><figcaption>Figure 29.5 \u2014 Oligodendroglioma planning. Source: Target Volume Delineation and Field Setup, 2nd Edition<\/figcaption><\/figure>\n<table>\n<thead>\n<tr>\n<th>Tumor type<\/th>\n<th>GTV definition<\/th>\n<th>Suggested CTV expansion<\/th>\n<th>PTV expansion<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Grade I pilocytic astrocytoma<\/td>\n<td>Unresected: post-contrast T1 MRI; resected: post-operative cavity<\/td>\n<td>0\u20130.5 cm, reduced around natural anatomic barriers<\/td>\n<td>0\u20130.3 cm technique-dependent; 0\u20131 mm SRS\/HSRT; 1\u20133 mm conventional RT<\/td>\n<\/tr>\n<tr>\n<td>Ganglioglioma<\/td>\n<td>Unresected: post-contrast T2 or FLAIR MRI; resected: cavity + residual tumor<\/td>\n<td>1 cm, reduced around natural barriers<\/td>\n<td>0.3\u20130.5 cm depending on IGRT frequency and technique<\/td>\n<\/tr>\n<tr>\n<td>Grade II low-grade diffuse glioma (IDH-mutated)<\/td>\n<td>Unresected: T2 or FLAIR MRI; resected: cavity + residual tumor<\/td>\n<td>1 cm, reduced around natural barriers<\/td>\n<td>0.3\u20130.5 cm depending on IGRT frequency and technique<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><em>Source: Target Volume Delineation and Field Setup, 2nd Edition (Table 29.2)<\/em><\/p>\n<p>The oligodendroglioma case in Figure 29.5 shows a patient after left frontotemporoparietal craniotomy with partial resection involving the left insula, portions of the operculum, and extending into the left centrum semiovale. The GTV (red) encompasses FLAIR residual disease and the post-operative cavity. A 1.0 cm expansion generates the CTV (yellow) with anatomic restriction out of the posterior fossa, skull, and midline structures. The PTV (blue) receives an additional 0.3 cm margin.<\/p>\n<h2>Grade 1 meningiomas: doses, techniques, and contouring<\/h2>\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" class=\"alignleft lazyload\" data-src=\"https:\/\/rtmedical.com.br\/wp-content\/uploads\/2026\/04\/benign-cns-meningioma-srs-plan.jpeg\" alt=\"T1 post-contrast MRI treatment planning for right frontal convexity meningioma treated with single-fraction SRS showing GTV and 14 Gy, 8 Gy, and 4 Gy isodose lines\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 690px; --smush-placeholder-aspect-ratio: 690\/500;\"><figcaption>Figure 29.6 \u2014 Frontal meningioma, SRS plan. Source: Target Volume Delineation and Field Setup, 2nd Edition<\/figcaption><\/figure>\n<p>Meningiomas are the most common primary intracranial tumors in adults \u2014 over 70% are benign and suitable for definitive radiotherapy. For grade 1 meningiomas with subtotal resection in areas at high risk for symptomatic progression, adjuvant therapy is considered. For the remainder, repeat surgery and radiation therapy are reserved for recurrence.<\/p>\n<h3>Recommended dose and fractionation schedules<\/h3>\n<table>\n<thead>\n<tr>\n<th>Radiation technique<\/th>\n<th>Suggested dose\/fractionation<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>SRS<\/td>\n<td>14\u201316 Gy in 1 fraction<\/td>\n<\/tr>\n<tr>\n<td>FSRT<\/td>\n<td>20\u201324 Gy in 4 fractions; 25 Gy in 5 fractions<\/td>\n<\/tr>\n<tr>\n<td>Conventionally fractionated RT<\/td>\n<td>52.2\u201354 Gy at 1.8\u20132 Gy\/fraction; 50.4 Gy at 1.8 Gy\/fraction for optic nerve sheath meningiomas<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><em>Source: Target Volume Delineation and Field Setup, 2nd Edition (Table 29.3)<\/em><\/p>\n<h3>Target volumes for meningiomas<\/h3>\n<table>\n<thead>\n<tr>\n<th>Clinical scenario<\/th>\n<th>GTV definition<\/th>\n<th>CTV expansion<\/th>\n<th>PTV expansion<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Grade 1 unresected<\/td>\n<td>Tumor delineated on planning MRI and CT simulation<\/td>\n<td>0\u20130.5 cm, reduced around natural anatomic barriers<\/td>\n<td>0\u20131 mm (SRS\/HSRT); 1\u20133 mm (conventional RT)<\/td>\n<\/tr>\n<tr>\n<td>Grade 1 recurrent<\/td>\n<td>Post-operative cavity, residual enhancing tumor including suspicious dural and\/or bone involvement, and prior dural attachment<\/td>\n<td>Anatomically constrained 0\u20130.5 cm expansion<\/td>\n<td>0\u20131 mm (SRS\/HSRT); 1\u20133 mm (conventional RT)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><em>Source: Target Volume Delineation and Field Setup, 2nd Edition (Table 29.4)<\/em><\/p>\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" class=\"alignright lazyload\" data-src=\"https:\/\/rtmedical.com.br\/wp-content\/uploads\/2026\/04\/benign-cns-cavernous-sinus-meningioma-2.jpeg\" alt=\"Treatment planning CT for right cavernous sinus meningioma treated to 52.2 Gy in 29 fractions with GTV, PTV, and colorwash isodose lines including brainstem, chiasm, and cranial nerves\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 623px; --smush-placeholder-aspect-ratio: 623\/518;\"><figcaption>Figure 29.7 \u2014 Cavernous sinus meningioma, fractionated RT. Source: Target Volume Delineation and Field Setup, 2nd Edition<\/figcaption><\/figure>\n<p>A critical practical point: CT evaluation is essential to decide whether periosteal and bone changes should be included within the GTV. The cavernous sinus meningioma in Figure 29.7 was delineated using a treatment planning MRI, received a 2 mm margin to generate the PTV, and was treated to 52.2 Gy in 29 fractions. Colorwash isodose lines confirm tight conformality around the brainstem, chiasm, adjacent cranial nerves, carotid artery, and right cochlea.<\/p>\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" class=\"alignleft lazyload\" data-src=\"https:\/\/rtmedical.com.br\/wp-content\/uploads\/2026\/04\/benign-cns-sellar-meningioma-plan.jpeg\" alt=\"Treatment planning CT and MRI for a massive sellar and suprasellar Grade 1 meningioma with significant residual disease after debulking, showing 3 mm PTV expansion\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 690px; --smush-placeholder-aspect-ratio: 690\/322;\"><figcaption>Figure 29.8 \u2014 Large sellar meningioma, residual disease. Source: Target Volume Delineation and Field Setup, 2nd Edition<\/figcaption><\/figure>\n<p>Massive sellar and suprasellar meningiomas with incomplete resection \u2014 as in Figure 29.8 \u2014 may require a 3 mm PTV expansion given the extent of residual disease. The intimate relationship with both globes and the brainstem mandates careful dosimetric planning, often with IMRT or VMAT to conform the prescription dose while sparing these critical structures.<\/p>\n<h2>Vestibular and non-vestibular schwannomas<\/h2>\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" class=\"alignright lazyload\" data-src=\"https:\/\/rtmedical.com.br\/wp-content\/uploads\/2026\/04\/benign-cns-schwannoma-target-volumes-1.jpeg\" alt=\"Axial T1 post-contrast MRI of right cerebellopontine angle vestibular schwannoma compressing the middle cerebellar peduncle and pons with extension into the internal auditory canal\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 690px; --smush-placeholder-aspect-ratio: 690\/638;\"><figcaption>Figure 29.9 \u2014 Vestibular schwannoma in the CPA. Source: Target Volume Delineation and Field Setup, 2nd Edition<\/figcaption><\/figure>\n<p>Vestibular and non-vestibular schwannomas can be treated with radiation therapy as definitive treatment, adjuvant therapy after partial resection, or \u2014 rarely \u2014 for recurrence. A distinctive feature of these tumors: no CTV margin is added. The GTV is delineated directly on T1 post-contrast MRI and CT simulation, and only a technique-dependent PTV margin is applied.<\/p>\n<h3>Techniques and target volumes for schwannomas<\/h3>\n<table>\n<thead>\n<tr>\n<th>Technique<\/th>\n<th>Dose\/fractionation<\/th>\n<th>GTV<\/th>\n<th>CTV<\/th>\n<th>PTV<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>SRS<\/td>\n<td>12\u201313 Gy in 1 fraction<\/td>\n<td>Tumor on MRI + CT<\/td>\n<td>None<\/td>\n<td>0\u20131 mm<\/td>\n<\/tr>\n<tr>\n<td>FSRT<\/td>\n<td>20 Gy\/4 fractions or 25 Gy\/5 fractions<\/td>\n<td>Tumor on MRI + CT<\/td>\n<td>None<\/td>\n<td>0\u20131 mm<\/td>\n<\/tr>\n<tr>\n<td>Conventional RT<\/td>\n<td>46.8\u201354 Gy at 1.8\u20132 Gy\/fraction<\/td>\n<td>Tumor on MRI + CT<\/td>\n<td>None<\/td>\n<td>0\u20133 mm<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><em>Source: Target Volume Delineation and Field Setup, 2nd Edition (Table 29.5)<\/em><\/p>\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" class=\"alignleft lazyload\" data-src=\"https:\/\/rtmedical.com.br\/wp-content\/uploads\/2026\/04\/benign-cns-schwannoma-cpa-mri.jpeg\" alt=\"Axial and coronal T1 post-contrast MRI of left cerebellopontine schwannoma extending into internal auditory canal with 12.5 Gy prescription, 20 Gy, and 5 Gy isodose lines\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 690px; --smush-placeholder-aspect-ratio: 690\/418;\"><figcaption>Figure 29.10 \u2014 Left CPA schwannoma, SRS plan. Source: Target Volume Delineation and Field Setup, 2nd Edition<\/figcaption><\/figure>\n<p>The case in Figure 29.9 illustrates a right CPA vestibular schwannoma compressing the middle cerebellar peduncle and pons, extending into the fundus of the internal auditory canal. There is brainstem compression and compression of the right cisternal trigeminal nerve with moderate partial effacement of the fourth ventricle. Figure 29.10 shows treatment of a left CPA schwannoma with SRS: the 12.5 Gy prescription isodose covers the tumor, with a 20 Gy isodose concentrated in the tumor center and the 5 Gy isodose line at the periphery, preserving the brainstem and cochlea.<\/p>\n<h2>Pituitary adenomas: contouring and planning<\/h2>\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" class=\"alignright lazyload\" data-src=\"https:\/\/rtmedical.com.br\/wp-content\/uploads\/2026\/04\/benign-cns-pituitary-srs-plan.jpeg\" alt=\"Axial, coronal, and sagittal T1 post-contrast MRI of growth hormone-secreting pituitary adenoma treated with SRS at 24 Gy showing isodose lines and optic chiasm\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 690px; --smush-placeholder-aspect-ratio: 690\/439;\"><figcaption>Figure 29.11 \u2014 GH-secreting pituitary adenoma, SRS 24 Gy. Source: Target Volume Delineation and Field Setup, 2nd Edition<\/figcaption><\/figure>\n<p>Non-functional pituitary adenomas are typically treated with SRS, HSRT, or conventionally fractionated radiotherapy in the adjuvant or salvage setting after resection. Functional adenomas may receive hormonal therapy or surgery before radiation is considered, depending on the tumor subtype. High-resolution, thin-slice MRI of the pituitary in coronal and sagittal planes is essential for target delineation. Adenomas are best visualized in the early phase of gadolinium-enhanced dynamic imaging, appearing as a hypointense lesion against the hyperintense normally enhancing pituitary gland.<\/p>\n<h3>Recommended doses for pituitary adenomas<\/h3>\n<table>\n<thead>\n<tr>\n<th>Technique<\/th>\n<th>Dose\/fractionation<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>SRS \u2014 Non-functional<\/td>\n<td>15\u201316 Gy in 1 fraction<\/td>\n<\/tr>\n<tr>\n<td>SRS \u2014 Functional\/secretory<\/td>\n<td>18\u201325 Gy in 1 fraction (>20 Gy preferred) based on optic nerve\/chiasm tolerance<\/td>\n<\/tr>\n<tr>\n<td>Conventional RT \u2014 Non-functional<\/td>\n<td>45\u201350.4 Gy at 1.8\u20132 Gy\/fraction<\/td>\n<\/tr>\n<tr>\n<td>Conventional RT \u2014 Functional\/secretory<\/td>\n<td>54\u201355.8 Gy at 1.8\u20132 Gy\/fraction<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><em>Source: Target Volume Delineation and Field Setup, 2nd Edition (Table 29.6)<\/em><\/p>\n<h3>Target volumes for pituitary adenomas<\/h3>\n<table>\n<thead>\n<tr>\n<th>Clinical scenario<\/th>\n<th>GTV definition<\/th>\n<th>CTV expansion<\/th>\n<th>PTV expansion<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Unresected \/ focal residual \/ focal recurrent<\/td>\n<td>Tumor delineated on planning MRI and CT simulation<\/td>\n<td>0\u20130.5 cm, reduced around natural anatomic barriers<\/td>\n<td>0\u20131 mm (SRS\/HSRT); 1\u20133 mm (conventional RT)<\/td>\n<\/tr>\n<tr>\n<td>Resected with residual or recurrent disease<\/td>\n<td>Tumor delineated on planning MRI and CT simulation<\/td>\n<td>0\u20130.5 cm, reduced around natural barriers and to pre-operative disease extension<\/td>\n<td>0.3\u20130.5 cm depending on IGRT frequency and technique<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><em>Source: Target Volume Delineation and Field Setup, 2nd Edition (Table 29.7)<\/em><\/p>\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" class=\"alignleft lazyload\" data-src=\"https:\/\/rtmedical.com.br\/wp-content\/uploads\/2026\/04\/benign-cns-pituitary-preop-postop.jpeg\" alt=\"Pre-operative and post-operative T1 post-contrast MRI of non-secretory pituitary adenoma showing sellar tumor with suprasellar extension and right cavernous sinus invasion\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 690px; --smush-placeholder-aspect-ratio: 690\/762;\"><figcaption>Figure 29.12 \u2014 Pituitary adenoma pre- and post-operative MRI. Source: Target Volume Delineation and Field Setup, 2nd Edition<\/figcaption><\/figure>\n<p>The GH-secreting adenoma in Figure 29.11 demonstrates SRS treatment at 24 Gy in a single fraction. The tumor abuts the medial margin of the right cavernous carotid and extends between the carotid loops laterally with cavernous sinus involvement superiorly. The dose to the chiasm, optic nerves, and brainstem was kept below 8 Gy each. Figure 29.12 shows a non-secretory adenoma centered in the sella extending into the suprasellar cistern, displacing the optic chiasm and invading the right cavernous sinus \u2014 after resection, residual tumor persisted in the sella and cavernous sinus.<\/p>\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" class=\"alignright lazyload\" data-src=\"https:\/\/rtmedical.com.br\/wp-content\/uploads\/2026\/04\/benign-cns-pituitary-fractionated-plan.jpeg\" alt=\"Treatment planning CT for non-secretory pituitary adenoma after resection with GTV, CTV with 0.5 cm margin, and PTV with 0.3 cm margin, with brainstem and optic nerves delineated\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 421px; --smush-placeholder-aspect-ratio: 421\/945;\"><figcaption>Figure 29.13 \u2014 Post-resection pituitary adenoma, fractionated RT. Source: Target Volume Delineation and Field Setup, 2nd Edition<\/figcaption><\/figure>\n<p>Figure 29.13 shows the fractionated plan for the same patient: GTV outlined in coral, CTV with a 0.5 cm anatomically constrained margin in teal, and PTV with an additional 0.3 cm expansion. Brainstem, chiasm, and optic nerves are delineated as OARs. For macroadenomas, when cavernous sinus invasion is difficult to visualize, the recommendation is to include the entire cavernous sinus within the GTV. Knowledge of the implanted material type in the sella (muscle, fat, or rotational nasal septal flap) helps differentiate it from residual tumor.<\/p>\n<h2>Glomus tumors and paragangliomas<\/h2>\n<p>Glomus tumors are rare neuroendocrine neoplasms that can arise at the skull base, head and neck, thorax, and abdomen, and are typically named based on their site of origin. Treatment options include embolization, resection, and radiation therapy, all achieving high local control rates. Careful assessment of diagnostic MRI and CT is essential for target delineation \u2014 potential invasion of the tympanic cavity, jugular foramen, petroclival region, cavernous sinus, or hypoglossal canal must be evaluated. CT in bone window is strongly recommended to assess for bony erosion.<\/p>\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" class=\"alignleft lazyload\" data-src=\"https:\/\/rtmedical.com.br\/wp-content\/uploads\/2026\/04\/benign-cns-glomus-tumor-fsrt-plan.jpeg\" alt=\"T2-weighted SPACE MRI, soft tissue CT, and dosimetric plan for a right-sided glomus tumor at the carotid bifurcation treated with 25 Gy in 5 fractions showing GTV and PTV\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 690px; --smush-placeholder-aspect-ratio: 690\/763;\"><figcaption>Figure 29.14 \u2014 Carotid body glomus tumor, FSRT 25 Gy\/5 fractions. Source: Target Volume Delineation and Field Setup, 2nd Edition<\/figcaption><\/figure>\n<h3>Dose prescriptions and target volumes for glomus tumors<\/h3>\n<table>\n<thead>\n<tr>\n<th>Technique<\/th>\n<th>Dose\/fractionation<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>SRS<\/td>\n<td>14\u201316 Gy in 1 fraction<\/td>\n<\/tr>\n<tr>\n<td>FSRT<\/td>\n<td>25 Gy in 5 fractions<\/td>\n<\/tr>\n<tr>\n<td>Conventional RT<\/td>\n<td>50.4\u201354 Gy at 1.8\u20132 Gy\/fraction<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><em>Source: Target Volume Delineation and Field Setup, 2nd Edition (Table 29.8)<\/em><\/p>\n<table>\n<thead>\n<tr>\n<th>GTV definition<\/th>\n<th>CTV expansion<\/th>\n<th>PTV expansion<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Tumor delineated on planning MRI and CT simulation<\/td>\n<td>0\u20130.5 cm, reduced around natural anatomic barriers<\/td>\n<td>0\u20131 mm (SRS\/HSRT); 1\u20133 mm (conventional RT)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><em>Source: Target Volume Delineation and Field Setup, 2nd Edition (Table 29.9)<\/em><\/p>\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" class=\"alignright lazyload\" data-src=\"https:\/\/rtmedical.com.br\/wp-content\/uploads\/2026\/04\/benign-cns-glomus-recurrent-plan.jpeg\" alt=\"Bone window CT for recurrent left-sided glomus tumor in jugular bulb after embolization and resection treated to 54 Gy in 30 fractions with GTV, PTV, and multiple OARs\" src=\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\" style=\"--smush-placeholder-width: 470px; --smush-placeholder-aspect-ratio: 470\/865;\"><figcaption>Figure 29.15 \u2014 Recurrent glomus tumor, 54 Gy\/30 fractions. Source: Target Volume Delineation and Field Setup, 2nd Edition<\/figcaption><\/figure>\n<p>Figure 29.14 shows a right-sided carotid body glomus tumor splaying the internal and external carotid arteries. The GTV (red) was delineated using T2 SPACE MRI co-registered to the CT, with a 3 mm expansion for the PTV (turquoise). The elderly patient received 25 Gy in 5 fractions, with colorwash isodose lines displaying the prescription dose (25 Gy), 110% volume (27.5 Gy), 80% volume (20 Gy), and 50% volume (12.5 Gy). Key nearby OARs \u2014 parotids, submandibular glands, oral cavity, and oropharyngeal wall \u2014 were carefully spared.<\/p>\n<p>The case in Figure 29.15 presents a more complex scenario: a recurrent left-sided glomus tumor in the jugular bulb after prior embolization and resection, treated to 54 Gy in 30 fractions. The GTV was generated by co-registering MR images from initial diagnosis and recurrence, encompassing the original disease extent, post-operative changes and tumor bed, and recurrent disease with skull base coverage. A 0.3 cm margin defined the PTV. Multiple OARs \u2014 brainstem, mandible, bilateral parotids, spinal cord with PRV, oropharyngeal wall, oral cavity, and lips \u2014 were meticulously delineated.<\/p>\n<h2>Clinical integration and technique selection<\/h2>\n<p>Delineating benign CNS tumors demands multimodal imaging integration \u2014 CT in various windows complemented by MRI with sequences tailored to each pathology. The choice between SRS, FSRT, and conventionally fractionated RT depends on tumor size, proximity to critical structures (especially the optic apparatus), and the clinical setting (definitive, adjuvant, or salvage). For a comprehensive overview of delineation approaches across all sites, see our <a href=\"#\">complete guide on target volume delineation and field setup<\/a>.<\/p>\n<p>Compact schwannomas and meningiomas are ideal candidates for SRS or FSRT, while larger tumors or those near the optic chiasm often require conventional fractionation to respect critical structure tolerances. Low-grade gliomas, given their infiltrative nature, demand larger CTV margins and judicious use of FLAIR MRI to capture disease extent. Glomus tumors require special attention to skull base anatomy and potential vascular invasion. Related articles that may complement your reading include our material on <a href=\"https:\/\/rtmedical.com.br\/en\/brain-metastases-wbrt-srs\/\">brain metastases and SRS<\/a> and on <a href=\"https:\/\/rtmedical.com.br\/en\/malignant-cns-delineation\/\">malignant CNS tumors<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Target delineation for benign CNS tumors: volumes, doses, and RT techniques for meningioma, schwannoma, pituitary adenoma, and glomus tumor.<\/p>\n","protected":false},"author":1,"featured_media":16709,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"ngg_post_thumbnail":0,"fifu_image_url":"","fifu_image_alt":"","footnotes":""},"categories":[265,98,271],"tags":[],"class_list":{"0":"post-14303","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-delineamento-volumes","8":"category-radioterapia","9":"category-delineamento-snc"},"aioseo_notices":[],"rt_seo":{"title":"Benign CNS Tumors RT: Target Delineation","description":"Target volume delineation for benign CNS tumors. Meningioma, vestibular schwannoma, pituitary adenoma SRS and fractionated RT planning.","canonical":"","og_image":"","robots":"default","schema_type":"MedicalWebPage","include_in_llms":false,"llms_label":"","llms_summary":"","faq_items":[{"q":"How is the GTV defined for meningioma radiotherapy?","a":"The GTV includes the contrast-enhancing tumor and any dural tail on MRI. For SRS, the GTV-to-PTV margin is 1-2 mm. For fractionated RT, a CTV margin of 2-5 mm is added to account for microscopic dural extension, and standard PTV margins of 3-5 mm are applied."},{"q":"What is the optimal dose for vestibular schwannoma SRS?","a":"The standard SRS dose for vestibular schwannoma is 12-13 Gy to the 50% isodose line in a single fraction. This achieves tumor control rates exceeding 95% while preserving serviceable hearing in approximately 50-70% of patients. Fractionated RT uses 50.4-54 Gy in 28-30 fractions."},{"q":"How are pituitary adenomas delineated for RT?","a":"The GTV is defined on contrast-enhanced MRI with CT fusion for bony anatomy. The CTV includes the GTV with a small margin for microscopic extension into the cavernous sinus. Optic chiasm, optic nerves, and brainstem are the critical OARs requiring strict dose constraints."}],"video":[],"gtin":"","mpn":"","brand":"","aggregate_rating":[]},"_links":{"self":[{"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/posts\/14303\/"}],"collection":[{"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/posts\/"}],"about":[{"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/types\/post\/"}],"author":[{"embeddable":true,"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/users\/1\/"}],"replies":[{"embeddable":true,"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/comments\/?post=14303"}],"version-history":[{"count":3,"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/posts\/14303\/revisions\/"}],"predecessor-version":[{"id":16797,"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/posts\/14303\/revisions\/16797\/"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/media\/16709\/"}],"wp:attachment":[{"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/media\/?parent=14303"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/categories\/?post=14303"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/tags\/?post=14303"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}