Low Grade Gliomas

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LOW GRADE GLIOMAS

DR ARNAB BOSE Dept. of RadiotherapyNRS Medical Colleg,Kolkata

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Low-grade gliomas are a pathologically and clinically diverse

group of uncommon central nervous system (CNS) tumors

that occur primarily in children and young adults.

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The concept of dividing astrocytomas into discrete grades

associated with a distinct clinical prognosis dates back to the

mid-1920s and early 1930s to the work of Bailey and Cushing,

who recognized a subset of astrocytomas that had a more

favorable outcome than glioblastoma.

There have been many grading systems (e.g., Kernohan, St. Anne-Mayo, and Ringertz systems)

in the past, and most of these grading systems share an

assessment of nuclear abnormalities, mitoses, endothelial proliferation, and

necrosis, but the most widely used and accepted grading system

today is the WHO system.

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WHO Grade I lesions have low proliferative potential, withthe possibility of cure following surgery alone. WHO Grade II neoplasms are infiltrative, often recur, and

tend to progress to higher grades of malignancy (e.g., grade II

astrocytomatransforms to grade III anaplastic astrocytoma) despite low

levelproliferative activity.

All grading schemes are limited by their need to separate gliomas

artificially into three or four groups, when in actuality they exist along a

biologic continuum.

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Type WHO Grade

Astrocytic TumorsSubependymal giant cell astrocytomas IPilocytic astrocytomas IPleomorphic xanthoastrocytomas IIDiffuse astrocytoma II

Oligodendroglial TumorsOligodendrogliomas II

Oligoastrocytic TumorsOligoastrocytomas II

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Low-grade astrocytomas make up 5% to 15% of adult primary brain

tumors and 67% of low-grade gliomas, the remainder of low-grade gliomas being mixed

Oligoastrocytomas (19%) and Oligodendrogliomas (13%).

Astrocytic gliomas, arise from astrocytes, the supporting cells of the

brain and spinal cord. The cytoplasmic processes that extend from the

astrocytes contain a characteristic filamentous protein, glial fibrillary acidic protein (GFAP), which provides an immunohistochemical marker for these tumors.

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The Diffusely infiltrative low-grade astrocytomas (WHO grade II)

are the most common and include the fibrillary, protoplasmic, and

gemistocytic types.

They represent 70% of low-grade cerebral astrocytomas.

Diffuse astrocytomas are usually poorly circumscribed and are

capable of undergoing anaplastic transformation.

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Fibrillary astrocytomas, the most common subtype, and Protoplasmic astrocytomas have been referred to as “ordinary” astrocytomas and share a similar prognosis. Over time, at least

50% of these tumors transform into more anaplastic lesions.

Gemistocytic astrocytomas are composed of large, plump astrocytes

with abundant eosinophilic cytoplasm. Gemistocytes commonly transform into highly anaplastic cells, and behave in an

aggressive fashion. 

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The Pilocytic astrocytomas (WHO grade I), which comprisenearly all of the remainder of the cerebral astrocytomas, tendto be better circumscribed. They are composed of fusiform cells

with unusually long, wavy processes called Rosenthal fibers. Mitosis

is rarely seen. Pilocytic astrocytomas have a long natural history and

rarely transform. Although they occur more commonly in the

cerebellumof children (juvenile pilocytic astrocytoma), they alsooccur in the cerebral hemispheres and near the optic tracts.

Remaining are the uncommon low-grade glioma variants,including the Pleomorphic Xanthoastrocytomas, SubependymalGiant Cell Astrocytomas, and Dysembryoblastic Neuroepithelial

tumor.

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A two-tiered system, low-grade and anaplastic, is used to grade Oligodendrogliomas. In the WHO classification low-grade lesions are labeled grade II and anaplastic lesions are labeled as grade III.

Patients with grade II tumors have a median survival of 9.8 years whereas those with grade III tumors have a median survival of 4.6 years.

An important additional diagnostic assessment that should be performed on all oligodendroglial tumors is for the presence of deletions of chromosomes 1p and 19q. If these deletions are present, tumors tend to behave more indolently and are more responsive to therapy (especially chemotherapy).

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Many oligodendrogliomas are admixed with astrocytoma or

ependymoma components. The presence of up to 50% astroglial

component is accepted to make the diagnosis of mixed Oligoastrocytoma in the WHO classification.

The median survival for patients with low-grade mixed oligoastrocytomas is 7 years.

Most oligoastrocytomas and 50% to 75% of oligodendrogliomas

recur as AAs or GBM. 

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Tumor Proliferation can be assessed with Ki-67 labeling.

A large review on Ki-67 labeling revealed increasing values

of Ki-67/MIB-1 labeling index with increasing grade of malignancy.

The MIB-1 labeling index differentiates diffuse astrocytomas

(WHO grade II) from anaplastic astrocytomas (WHO grade III) and

glioblastoma multiforme (GM) tumors.

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Biologic Characteristics :

Combined 1p and 19q deletions are associated with a superior

outcome and are most common in oligodendrogliomas. TP53 mutations are more common in diffuse astrocytomas

and aremutually exclusive from 1p/19q co-deletions.

IDH1 mutations occur in the vast majority of low-grade gliomas and

are found both in tumors with TP53 mutations and in tumors with

1p/19q co-deletions.

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Low-grade gliomas are generally a disease of patients in their

20s, 30s, or 40s.

The most common symptom is seizure, occurring intwo thirds of patients. Focal seizures are more common

thangeneralized ones. Headache and weakness occur in approximately one

third of patients. The remaining symptoms (vomiting, motor deficit,

visual or sensory loss, language disturbance, or personality

change)occur in 15% or fewer patients.

Symptoms may be present for months or years before a diagnosis is

made.

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MRI : T1 - pre and post-gadolinium(contrast), T2, and FLAIR (fluid attenuation inversion recovery,

removes increased CSF signal on T2).

Tumor enhancement with gadolinium correlates with breakdown of

the blood–brain barrier.

Tumor: High grade – increased signal on T1 post-gadolinium

and T2 (T2 also shows edema).

Low grade – increased signal on T2 / FLAIR.

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Pilocytic astrocytoma (Grade I) : enhancing nodule, highly vascular, 50% associated with cysts.

Diffuse astrocytoma (Grade II) : non-enhancing, hypo-intense on T1, hyper-intense on

T2/FLAIR , well-circumscribed, solid.

Oligodendroglioma : calcifications associated frequently

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A Prognostic Scoring system was developed using imaging, patient,

and tumor characteristics derived from the databases of two large

phase III adult low grade glioma trials (EORTC trials 22844 and

22845). The following negative risk factors were identified and

validated: age 40 years or older, astrocytoma histology subtype(compared

to oligo/mixed), largest diameter of the tumor of 6 cm or

more, tumor crossing the midline, and presence of neurologic deficit before

surgery.

The presence of 2 of these factors or fewer identified a low-risk

group (median survival, 7.7 years), whereas 3 risk factors or more identified a high-risk

group (median survival, 3.2 years).

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Observation

The decision to Observe a patient with low-grade glioma has

been justified in the literature for several reasons. Thesereasons include the relatively favorable natural history of thedisease, the lack of proven benefit for invasive interventionssuch as surgical resection or radiation therapy, and the

potentialmorbidities of treatment.

Patients who are observed should be monitored at regular intervals

(e.g., every 6 months) to detect radiologic progression before new

signs and symptoms occur.

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Despite the favorable survival rates observed in certain subsets of

patients with low-grade gliomas, the natural history of all pathologic types of supratentorial low-grade gliomas, including the pilocytic astrocytomas (WHO I), diffuse astrocytomas, oligoastrocytomas,

and oligodendrogliomas (WHO II), is significantly worse than that of an age- and sex matched control population, for which the expected survival rate is greater than 95%.

Based on this observation, some have argued that all such patients

should undergo Maximal Safe Surgical Resection followed bypostoperative radiation therapy.

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Surgery vs. Observation

Pros: i)If symptoms are uncontrolled medically, then benefits of surgery on seizures / raised ICT are fairly dramatic ii)Imaging can be misleading in upto 40% cases iii)Early Surgery delays reappearance of symptoms and

tumor growth iv)Survival advantage to gross resection in retrospective literature

Cons: i)Possibility of complications in a minimally symptomatic person

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Surgery

The key surgical issues in the management of supratentorial

low- grade gliomas are : whether to perform a biopsy on a patient

whose clinical presentation and imaging studies suggest a low-grade

glioma, and what should be the extent of resection.

Although one series in the literature suggests that the survival rate

of patients irradiated for presumed low-grade glioma is comparable to

that of patients irradiated for histologically verified low-grade

astrocytoma, the possibility of inappropriate management in up to

50% of cases diagnosed by imaging underscores the need for

histologic verification if a therapeutic intervention is planned.

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A number of retrospective studies have suggested a benefit for

greater extent of resection.

A long-term follow-up (median, 13.6 years) study fromthe Mayo Clinic reviewed 314 adult low-grade glioma patients

and found on multivariate analyses significantly improved OS and

PFS rates with gross total resection or nearly gross total resection.

Almost 50% of patients after gross total resection or nearly gross

total resection were free of recurrence 10 years after diagnosis.

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Investigators from the University of California San Francisco (UCSF) measured tumor volumes based on FLAIR imaging in 216 low-grade glioma patients.

Patients with at least 90% extent of resection had 5- and 8-year OS of

97% and 91%, respectively, whereas patients with less than 90% extent

of resection had 5- and 8-year OS of 76% and 60%, respectively. After adjusting for age, Karnofsky performance status (KPS) score, tumor location, and tumor subtype, OS and PFS outcomes were

both predicted by post-operative tumor volume.

Limitation of this study was the relatively short follow-up (4.4yrs).

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Prospective trials have also found a benefit for greater extent of

resection. The phase II portion of RTOG 9802 prospectively observed 111 low-risk cases after neurosurgically

defined gross total resection. Review of the post-operative MRI

emphasized the importance of post-operative imaging to confirm the

extent of resection because a substantial minority of patients

had residual disease (32% with 1 to 2 cm of residual disease and

9% with more than 2 cm of residual tumor). The crude incidence of tumor recurrence was 26% with

a residual tumor of less than 1 cm, 68% with a residual tumor of

1 to 2 cm, and 89% with a residual tumor of more than 2 cm.

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Although there are no randomized trials that directly assess the

impact of maximal tumor resection in low-grade gliomas, a review of

the literature suggests a benefit for Maximal Safe tumor Resection,

recognizing the importance of achieving this with as little morbidity as

possible.

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External Beam Radiation

The key external beam irradiation (EBRT) issues in the

management of supratentorial low-grade gliomas are twofold.

The issues include the timing of radiation with regard to when

radiation is given (post-operative vs. at the time of recurrence), and the appropriate dose and treatment volume.

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EORTC 22845 (Karim et al. 2002; van den Bent et al. 2005) –phase III: 311 patients (WHO 1–2, 51% astro., 14% oligo., 13%mixed oligo-astro) treated with surgery (42% GTR, 19% STR,35% biopsy) randomized to observation vs. post-op RT to 54 Gy.

RT improved median PFS (5.3 year vs. 3.4 year), 5-year PFS (55 vs.

35%), but not OS (68 vs. 66%). Sixty-five percent of patients in the

observation arm received salvage RT.

No difference in rate of malignant transformation (66–72%).

No survival benefit, but RT delays time to relapse by ~2 years.

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The RTOG phase II portion of protocol 9802 prospectively

observed 111 low-risk (age younger than 40 years and neuro-surgically

defined gross total resection) low-grade glioma patients.

In this “low-risk” population, the 5-year OS was 93%. Astrocytoma histology, residual tumor of 1 cm or more according to MR

imaging, and pre-operative tumor diameter of 4 cm or morewere found to be predictive of a poorer PFS.

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In patients with all three unfavorable prognostic factors, the 2- and 5-year rates of PFS were 60% and 13%, respectively.

In patients with none of the three unfavorable prognostic factors, the 2- and 5-year rates of PFS were 100% and 70%, respectively.

These data suggest that observation is a reasonable strategy for the most favorable subset (<1 cm residual tumor, preoperative tumor diameter <4 cm, and oligodendroglioma histology) of younger

patients after a gross total resection (GTR).

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Radiation, however, has several other beneficial effects besides the potential delay in tumor recurrence.

In a small series of 25 patients with medically intractable epilepsy

resulting from an underlying cerebral low-grade glioma, achieved a

significant reduction (>50% decrease) in seizure frequency after radiotherapy.

In the EORTC phase III randomized trial 22845, there were no differences in seizure control at baseline, but at 1 year there were significantly fewer seizures in the irradiated group (25%) than in

the observation group (41%).

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It has been suggested that radiation therapy may either increase or

decrease the likelihood of malignant transformation or may delay its onset.

However, in the EORTC phase III randomized trial 22845, there were no differences in the malignant transformation rate (observation group-66% vs.72% in the irradiated group) between the study arms at the time of progression.

These data imply that irradiation neither increases nor decreases the

likelihood of malignant transformation, suggesting that dedifferentiation

is a biologic phenomenon observed in low-grade gliomas independent

of the treatment.

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Dose of Radiation

Regarding the potential benefit of higher doses of radiation

therapy compared with lower doses, two prospective randomized

clinical trials (EORTC 22844 and NCCTG 86-72-51) failed

to show improved outcome with higher radiation therapy doses.

Taken together these trials support moderate doses in the

range of 45 to 54 Gy using localized fields.

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EORTC 22844 (Karim et al. 1996) – phase III: 343 patients(WHO 1–2, astro., oligo. and mixed) treated with surgery (25%

GTR, 30% STR, 40% biopsy) randomized to post-op RT 45 Gy vs. 59.4

Gy radiation therapy using multiple localized treatment fields. Initial analysis failed to demonstrate a difference in survival rates between the two doses. The 5-year OS was 58% with 45 Gy and

59%with 59.4 Gy.

Five-year OS oligo vs. astro = 75 vs. 55%, <40 year vs. >40 year = 80 vs. 60%. Age <40 year, oligo histology, low T-stage, GTR, and good

neurologic status are important prognostic factors.

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INT/NCCTG (Shaw et al. 2002) – phase III: 203 patients (WHO 1–2, astro, oligo, mixed) treated with surgery (14% GTR, 35% STR, 51% Bx) randomized to post-op RT 50.4 Gy vs. 64.8

Gy. also using multiple localized treatment fields.

Initial analysis also failed to demonstrate a difference in survival

rates between the two doses. The 5-year OS was 73% with50.4 Gy and 68% with 64.8 Gy.

Best survival in patients <40 year, tumor <5 cm, oligo histology and

GTR.

Pattern of failure: 92% in field, 3% within 2 cm of RT field.

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Several series analyzing failure patterns in irradiated patients with

low-grade hemispheric gliomas suggest that when tumor progression

occurs, it almost always is at the site of the primary tumor within the

treatment volume, which implies that Partial Brain Irradiation is appropriate.

This was confirmed in NCCTG 86-72-51 (prospective dose response trial) with 92% of failures occurring in the treatment

field, 3% within 2 cm of the treatment field, and 5% more than 2 cmbeyond the treatment field. These data support the appropriateness of partial brain

irradiation.

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Several phase II Chemotherapy studies have shown efficacy ofboth Temozolomide and PCV (procarbazine,CCNU, vincristine) chemotherapy in either newly diagnosed or progressing low-

grade gliomas.

The studies on newly diagnosed tumors show that the response

assessment may be difficult, and that most cases have radiologically

stable disease as their best response to chemotherapy(at times, even despite clinical improvement and improvedseizure control). As a result, the PFS appears to be a more informative endpoint

than the radiologic improvement rate.

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Data from phase III studies on chemotherapy in low-gradegliomas are scarce.

The most significant study is the INT/RTOG 9802 trial (ASCO abstract 2008): phase III of low-grade gliomas. Low-risk (<40 year + GTR) observed until symptoms.251 high-risk (>40 year or STR or biopsy) patients

randomized to RT alone vs. RT --> PCV ×6 cycles q8 weeks. RT 54 Gy to FLAIR + 2 cm margin. No boost. Five-year OS was 72 vs. 63% (p = 0.33), 5-year PFS was 63

vs. 46%(p = 0.06) in favour of addition of chemotherapy.

This study noted an increase of PFS but not OS with radiotherapy

followed by PCV chemotherapy.

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Recently, Temozolomide has shown its effectiveness in the initial

treatment of low-grade glioma.

In the largest reported retrospective analysis of 149 patients,

Kaloshi and colleagues reported a 15% partial response (PR) and 37%

stable disease with temozolomide as the initial therapy. The median

PFS was 2.8 years and the 3-year overall survival was 70%.*

*(Kaloshi G, Benuaich-Amiel A, Diakite F, et al: Temozolomide for low grade gliomas: predictive impact of 1p/19q loss on response and outcome. Neurology  2007; 68:1831-1836.)

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Abstract of the study by Kaloshi et al

OBJECTIVE: To evaluate the predictive impact of chromosome 1p/19q deletions on the response and outcome of progressive low-grade gliomas

(LGG) treated with up-front temozolomide (TMZ) chemotherapy.

METHODS: Adult patients with measurable, progressive LGG (WHO grade II) treated with TMZ delivered at the conventional schedule (200 mg/m(2)/day for 5 consecutive days, repeated every 28 days)

were retrospectively evaluated for response by central review of MRI-s. Chromosome 1p and 19q deletions were detected by the loss of

the heterozygosity technique (LOH).

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RESULTS: A total of 149 consecutive patients were included in this retrospective, single center observational study. The median number of TMZ cycles delivered was 14 (range 2 to 30). 77 patients (53%) experienced an objective response (including 22 [15%] cases of partial response and 55 [38%] cases of minor response), 55 (37%) patients had stable disease, and 14 (10%) had a progressive disease. The median time to maximum tumor response was 12 months (range 3 to 30 months). The median progression-free survival (PFS) was 28 months (95% CI: 23.4 to 32.6). Combined 1p/19q LOH was present in 42% of the cases and was significantly associated with a higher rate (p = 0.02) and longer objective response to chemotherapy (p = 0.017), and both longer PFS (p = 4.10(-5)) and overall survival (p = 0.04).

CONCLUSION: Low-grade gliomas respond to temozolomide and loss of chromosome 1p/19q predicts both a durable chemosensitivity and a favorable outcome.

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An EORTC trial attempts to address the role of temozolomide in

newly diagnosed low-grade glioma patients. This EORTC trial randomizes patients with progressive disease, uncontrolled

seizures despite anticonvulsants, or neurologic symptoms to standard

radiation therapy or daily low-dose temozolomide. Patients are stratified

basedon 1p status (intact vs. deleted), as well as age, tumor size,and Karnofsky performance status (KPS) score with a primaryendpoint of PFS.

An Intergroup phase III trial with similar eligibility criteria and stratification factors is investigating the efficacy of combined chemoradiation with temozolomide compared with radiotherapy alone.

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Recommended Treatment

Juvenile Pilocytic Astrocytoma, Subependymal Giant Cell

Astrocytoma, Pleomorphic Xanthoastrocytoma,Dysembryoblastic Neuroepithelial tumor :

i) Gross Total Resection Observation

ii) Sub Total Resection consider Observation vs. Re-resection vs. Radiotherapy vs. Stereotactic Radiosurgery, depending on the location of tumor, symptoms, age of

patient

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Oligodendroglioma, Oligoastrocytoma, Astrocytoma (adults) :

i) Maximal safe resection (GTR or STR) Observation if - age <40 years, oligodendroglioma, GTR, good function Serial MRIs - if progresses Radiotherapy 50–54

Gy (standard dose for low-grade

gliomas is 54 Gy)

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Or,

ii) Immediate Post-operative Radiothrapy to 54 Gy. No survival benefit, but RT delays time to

relapse by ~2 years (EORTC study) Quality of life gained by delaying recurrence

must be weighted against QOL lost due to late

toxicities of RT

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Oligodendroglioma, Oligoastrocytoma, Astrocytoma (children) :

i) Maximal safe resection (GTR or STR) Observation and serial MRIs. Adjuvant Radiotherapy may improve DFS,

but not recommended for children <3 years.ii) Consider Second Surgery for operable progression,

and Radiotherapy for inoperable progression (doses 45–54 Gy)

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Dose : EBRT: 1.8 Gy/fx to 50.4–54 Gy. Volume of Treatment : Pilocytic AstrocytomasGTV: contrast-enhancing lesion and any associated cystPTV: GTV plus 1–1.5 cm Infiltrating Low-Grade GliomasGTV: (FLAIR)/T2 abnormality and any contrast

enhancementPTV: GTV plus 1–1.5 cm

Follow Up :MRI 2–6 weeks after Radiotherapy, then every 6 month

for 5 years, then annually.

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thank you