Bilateral occipital metastases: Visual deficits and management considerations

INTRODUCTION

Brain metastases are the most common intracranial tumors in adults, with a rising incidence as systemic disease control improves patient survival and screening increases with readily available imaging modalities.[3,5,10] The decision to treat brain metastases balances the benefits of tumor control, symptom alleviation, and survival with the risks of functional impairment and reduced quality of life.[6]

The nuanced impact of the treatment of brain metastases is highlighted in the scenario of metastases involving bilateral occipital lobes, which pose heightened risk to vision loss with or without intervention.[2] As patients with metastatic brain metastasis have a poor prognosis,[1] understanding risk of visual deterioration is vital in considering treatment. We, thus, sought to analyze the rates of visual change following radiation and/or surgery in patients with bilateral occipital metastases to abet decision-making in these challenging cases.

MATERIALS AND METHODS

Statistical analysis

The volumes of enhancing tumor and associated peritumoral edema were independently segmented (Brainlab, Munich, Germany) for analysis before and following treatment using T1 postcontrast and T2 fluid attenuation inversion recovery (FLAIR) MRI sequences [Figure 1]. Descriptive statistics and unadjusted linear regression analyses were conducted using the R package version 3.3.3.[14]

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Figure 1:: Representative image of patient with bilateral occipital metastases highlighting tumor size and edema. (a) A representative T1 postgadolinium contrast signal of a patient is highlighted. Segmentation of the solid tumor was used for quantitative volumetric analysis. (b) A representative T2 FLAIR sequence signal of a patient is highlighted. Segmentation of surrounding edema was used for quantitative volumetric analysis. The outlined portions are as follows: red is right tumor volume, orange is R tumor edema, purple is left tumor volume, and green is left tumor edema.

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RESULTS

Patient characteristics

Eighteen patients (13 women and 5 men) with bilateral occipital metastases were identified [Table 1], with a median age of 64 years (range 27–89 years). The most frequent primary cancers were lung (n = 10), melanoma (n = 3), and breast (n = 2). The 10 lung cancers included 3 adenocarcinomas, 2 large cell neuroendocrine tumors, 2 poorly differentiated tumors, 1 small cell lung cancer, and 2 with unknown histopathology. Both breast cancer metastases were triple-positive tumors, with immunopositivity for estrogen receptor, progesterone receptor, and herceptin-2 (HER2).

Table 1:: Patient characteristics.

Clinical presentation

Visual symptoms were present in 12 patients (67%) at time of presentation with bilateral occipital metastasis. These patients exhibited visual field deficit (67%), diplopia (17%), and visual acuity deficit (17%) on neurologic examination [Table 2].

Table 2:: Description of case series.

Visual symptoms before and after treatment

In patients with pretreatment visual deficits, no visual deficits worsened following treatment with either radiation or surgical resection plus radiation. Three patients remained with a stable deficit, whereas 9 of 12 patients improved. Of the three that did not improve, one patient had a biopsy rather than a gross total resection and presented with diplopia which was presumed secondary to a cavernous sinus metastasis [Table 2]. Of those that improved, approximately half showed signs of visual improvement by day 7 posttreatment, and all the patients who did improve showed signs of improvement by day 30 [Table 3a].

Table 3:: Visual symptoms following treatment.

In patients without pretreatment visual symptoms, half remained at baseline and half worsened throughout treatment. Of three patients who received radiation alone, one patient remained at baseline, one developed blurry vision which resolved within 1 week of treatment, and one developed a visual field cut within 1 day of treatment and subsequently died or was lost to follow up. Of three patients who received surgery plus radiation, two remained at baseline, whereas one patient developed a contralateral field cut, optic ataxia, and simultanagnosia (Balint’s syndrome) following 24 Gy of fractionated SRS. The patient then underwent surgical resection approximately 18 months later, and his visual deficits showed only miniscule improvement at 90 day follow-up [Table 3b].

Volumetric analysis

Nine of 18 patients had imaging pre- and postintervention available for volumetric analysis. Surgical resection showed greater reductions in postcontrast T1 volumes than radiation alone. Changes in FLAIR signal were variable across treatment modalities [Table 4].

Table 4:: Percent change in volume of tumor and surrounding edema for patients with available follow-up imaging.

Mortality

Patients who underwent surgical selection plus radiation tended to have a higher likelihood of survival than those who underwent radiation alone at various follow-up times [Figure 2]. In this cohort, median overall survival was 38 (range: 6–371) versus 387 (range: 43–1918) days for patients undergoing radiation alone versus surgical resection plus radiation, respectively (P = 0.15).

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Figure 2:: Kaplan–Meier curve showing percent of patients alive through 12-month follow-up stratified by treatment cohort.

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DISCUSSION

There is an absence of published experience in the management of patients with tumors involving bilateral occipital lobes.

A major risk of treating these patients is iatrogenic visual deficits, including cortical blindness, weighed against deficits conferred by the disease itself. In the setting of patients presenting with bilateral occipital metastases and unilateral visual field deficit, the decision to undergo bilateral treatment depends on extent of intracranial and extracranial tumor burden. In those with more severe tumor burden, unilateral treatment is favored to avoid unnecessary morbidity without a mortality benefit. When the bilateral occipital metastases are present in the setting of stable primary disease, treatment – especially surgical resection – may be safely conferred.

In our study, no patients who presented with visual deficits exhibited worsening of symptoms following treatment with any modality. Patients who presented with visual field deficit or blurry vision treated with surgical resection tended to gradually improve over days to weeks, likely due to relief of mass effect and reduction of edema.[15] Diplopia is unlikely related to tumor in the occipital lobe and does not appear to improve following treatment aimed at the occipital lobes. Patients who did not show improvement in visual deficits within the 1^st month of treatment were unlikely to show improvement at 90-day follow-up.

In patients without pretreatment visual deficits, the risk of iatrogenic visual deficits is an important consideration. In our cohort, one patient’s vision worsened months after radiation therapy which did not improve following surgical resection, and two patients’ vision worsened acutely following radiation alone. In terms of visual complications that may arise during treatment, one patient developed Bálint syndrome months following SRS. This may have been related to radiation, but could also have been tumor progression. Interestingly, the patient’s visual status did not improve following surgical resection.

Functional preservation is essential in patients with metastatic brain tumors to maximize quality of life. For patients who undergo surgical resection, meticulous care to preserve functional brain parenchyma, including selection of natural anatomic corridors to the surface of the tumor when subcortical, offers promising results in improving visual deficits in patients with bilateral occipital metastases. As subtotal resection is associated with decreased survival compared to a gross total resection, a gross total resection should be achieved when safely possible.[4]

Patients in our cohort who underwent surgical resection followed by radiation had markedly improved prognosis compared to radiation alone, which likely reflects selection bias in those patients deemed suitable for surgery. Our results appear consistent with literature in brain metastasis indicating improved survival benefit with surgical resection plus radiation compared to radiation alone.[9,13] In addition to treatment type, other considerations that have been shown to be significant risk factors for mortality are systemic tumor burden, intracranial tumor volume, and number of intracranial metastases.[8,11,12]

CONCLUSION

The management of bilateral occipital metastases involves consideration of symptomatology, disease burden, and goals of care. Patients often present with visual symptoms, which may improve following treatment, especially surgical resection. However, newly developed visual symptoms, including cortical blindness, are a potential consequence of treating these lesions. Surgical resection is a safe method for treatment in select patients with bilateral occipital metastases, especially if there is preoperative visual compromise, with careful consideration of anatomical corridors and brain parenchyma-sparing surgical technique.