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Requests for reprints should be addressed to Joseph A. Moore, MD, Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9030.
Of the many subtypes of non-Hodgkin lymphoma, small lymphocytic lymphoma/chronic lymphocytic leukemia comprises 18.3% and presents primarily with asymptomatic lymphadenopathy or abnormal complete blood count, or both. Central nervous system involvement with small lymphocytic lymphoma is rare.
Study Objective
The objective of this study was to report a case of small lymphocytic lymphoma presenting with hypopituitarism due to sellar involvement.
Case Description
A 71-year-old white man presented with fatigue, cold intolerance, and decreased alertness. The patient denied headache or visual changes. Physical examination was unremarkable, including normal visual fields. Laboratory studies revealed low thyroid-stimulating hormone (0.407) with low free T4 (0.034 ng/dL), indicating secondary hypothyroidism. Additional studies showed low testosterone (<3 ng/dL) and a depressed morning cortisol level (5.3 μg/dL). Contrast-enhanced T1-weighted magnetic resonance imaging of the brain revealed a 1.1 × 1.8 × 1.1-cm enhancing suprasellar mass, consistent with macroadenoma, abutting the optic chiasm without displacement (Figure). Transsphenoidal resection of the pituitary mass revealed small lymphocytic lymphoma. Bone marrow biopsy confirmed disease involvement from small lymphocytic lymphoma with 10%-20% involvement. The patient received radiation therapy to the pituitary using an involved site technique with 24 Gy given in 1.8- to 2-Gy fractions. Radiation was well tolerated and the patient is being monitored in follow-up with physical examinations, complete blood counts, and serial magnetic resonance imaging. Systemic therapy is being reserved for disease progression in this patient, who is currently asymptomatic.
FigureContrast-enhanced magnetic resonance imaging of the brain showing presurgical suprasellar mass (left) and postradiation therapy resolution of the pituitary (right).
Treatment of lymphoma involving the central nervous system is challenging due to the various degrees of difficulty for some drugs to cross the blood–brain barrier, resulting in sub-therapeutic concentrations of the medications in the cerebrospinal fluid. Medications such as methotrexate, when administered intravenously at high doses, can achieve therapeutic levels in the cerebrospinal fluid. Rituximab has also been used successfully in central nervous system lymphoma regimens for CD20+ lymphomas. Therapeutic challenges in this patient included a low mitotic rate and a low percentage of CD20 expression, which would be anticipated to limit the efficacy of CD20-targeted immunotherapy. Furthermore, given the indolent nature of small lymphocytic lymphoma and the localized, low disease burden in this patient, aggressive systemic therapy could be considered overtreatment. Given the radiosensitive nature of this histology, low to moderate doses of 20-24 Gy can achieve excellent tumor control with minimal long-term toxicity.
The therapeutic goal was local control. When administering radiation therapy to the pituitary region, dose-limiting toxicities include the proximity to the optic chiasm, with risk of visual loss occurring with doses above 45 Gy.
Anterior pituitary hormones are more radiosensitive at doses of 30 Gy or higher, and the majority of patients present with the typical temporal sequence of pituitary failure—growth hormone deficiency, gonadotropin deficiency, adrenocorticotropic hormone deficiency, and lastly, with thyroid-stimulating hormone deficiency.
However, radiation-induced hypopituitarism can present with any temporal sequence of hormonal deficiencies. The posterior pituitary is a more radio-resistant tissue, with only rare episodes of diabetes insipidus observed.
With regard to radiation dosimetry, there was a question as to the therapeutic efficacy of various radiation doses for the treatment of small lymphocytic lymphoma. This patient was successfully treated with radiation therapy to a total dose of 24 Gy and achieved complete radiographic resolution of the pituitary. He remains alive and asymptomatic with marrow-only involvement by small lymphocytic lymphoma 18 months after radiation therapy. The patient remains on levothyroxine, hydrocortisone, and testosterone replacement therapy. This case illustrates a rarely described presentation of a patient with small lymphocytic lymphoma manifesting as hypopituitarism. To the best of our knowledge, this represents only the fourth such case described.
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