Vol 27, No 3 (2022)
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Radical external radiotherapy of a solitary plasmacytoma of C1

Sara Zorro1, Mavilde Arantes2, Dora Gomes1, Isabel Oliveira3, Ângelo Oliveira1
Rep Pract Oncol Radiother 2022;27(3):589-590.


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clinical vignette

Reports of Practical Oncology and Radiotherapy

2022, Volume 27, Number 3, pages: 589–590

DOI: 10.5603/RPOR.a2022.0059

Submitted: 31.01.2022

Accepted: 04.05.2022

© 2022 Greater Poland Cancer Centre.
Published by Via Medica.
All rights reserved.

e-ISSN 2083–4640

ISSN 1507–1367

Radical external radiotherapy of a solitary plasmacytoma of C1

Sara Zorro1Mavilde Arantes2Dora Gomes1Isabel Oliveira3Ângelo Oliveira1
1Department of Radiation Oncology, Instituto Português de Oncologia do Porto, Porto, Portugal
2Department of Imaging, Instituto Português de Oncologia do Porto, Porto, Portugal
3Department of Hematology-Oncology, Instituto Português de Oncologia do Porto, Porto, Portugal

Address for correspondence: Sara Zorro, Department of Radiation Oncology, Instituto Português de Oncologia do Porto, Porto, Portugal; e-mail: sara.zorro@ipoporto.min-saude.pt

This article is available in open access under Creative Common Attribution-Non-Commercial-No Derivatives 4.0 International (CC BY-NC-ND 4.0) license, allowing to download articles and share them with others as long as they credit the authors and the publisher, but without permission to change them in any way or use them commercially

Key words: solitary plasmacytoma; craniocervical instability; radiotherapy
Rep Pract Oncol Radiother 2022;27(3):589–590

Solitary bone plasmacytoma (SBP) is defined as a single lytic lesion due to monoclonal plasma cell (PC) infiltration, with or without soft-tissue extension [1]. It represents 2–5% of PC malignancies [2].

Bone marrow aspiration and biopsy are required to evaluate PC morphology and infiltration. Additionally to computed tomography (CT), magnetic resonance image (MRI) or fluorodeoxyglucose positron emission tomography (FDG-PET) are needed to exclude additional lesions [1, 3].

SBP of the craniocervical junction is a rare tumour. When there is vertebral instability, surgical intervention is recommended, followed by radiation therapy [4].

SBP is highly sensitive to radiation. The recommended dose guidelines for SBP are total dose of 35 to 40 Gy (1.8–2 Gy daily fractions) for SBP < 5cm, and of 40 to 50Gy for SBP5cm [5].

55-year-old women presented in October of 2018 with aggravating neck pain for several years. She had worked as a cleaner for many years, never smoked or drunk alcohol. Medical and surgical history included hypertension, irritable bowel syndrome, asthma, depressive syndrome, and hemithyroidectomy. Medication included levothyroxine, indapamide, bisoprolol, escitalopram, and alprazolam. Her mother has type 2 diabetes, and one uncle has colon cancer. She has one healthy daughter.

Laboratory findings (complete blood cell count, and metabolic panel) and neurological exam were normal.

MRI and CT showed multiple cervical adenopathy and a single osteolytic lesion at the C1 vertebra (Fig. 1A) with 68.9 mm of transversal diameter, 31.2 mm of antero-posterior diameter, and 18.3 mm of craniocaudal diameter. No spinal cord compression was observed. FDG-PET showed diffuse hypermetabolism in cervical and oesophageal adenopathy without evidence of metastasis elsewhere.

The cervical lesion caused cranio-cervical instability, hence the decision for surgical biopsy and occipitocervical arthrodesis.

Figure 1. Solitary bone plasmacytoma (SBP) of C1 in a 55-year-old woman. A. Computed tomography (CT), in axial plane, showing C1 lesion predominantly involving the anterior arch and lateral masses, but also the posterior arch of this vertebra, especially on the right; B. CT, in axial plane, showing C1 lesion after the surgery and radiotherapy; C. Definitive radiation therapy, with the clinical target volume (CTV) (blue), and planning tumour volume (PTV) (red) illustrated in sagittal perspective; D. Isodose distribution curves, in sagittal perspective

Biopsy report of C1 was positive for lambda light chains plasmacytoma. The bone marrow biopsy was negative for neoplastic involvement.

The imaging, histologic and cytogenetic study concluded for a non-high-risk solitary plasmacytoma of C1 and excluded multiple myeloma. She was then proposed for localized radical external radiotherapy.

She underwent CT simulation for treatment planning, and the images were compared to diagnostic images of CT, MRI, and PET. C1 vertebra was defined as clinical target volume (CTV) on simulation CT. Planning tumour volume (PTV) was defined as 0.8 cm margin expansion from CTV, and a total dose of 40.0 Gy in 20 fractions was prescribed. Intensity-modulated radiotherapy (IMRT) plan was constructed (Fig. 1CD). A volumetric modulated arc therapy (VMAT) was chosen. The patient was treated for 28 days, with no interruptions, and experienced only dysgeusia and xerostomia throughout the treatment sessions.

Post-treatments CT showed occipital fixation, and less contrast-enhancement of the osteolytic lesion of C1 (Fig. 1B). The cervical lymph nodes were significantly smaller in diameter.

Both surgery and radiotherapy treatments caused neck rigidity. After physiotherapy, complaints were subsequently relieved, and neck mobility recovered.

The patient had poor oral health and needed several dental interventions during the treatment. Therefore, she never received bisphosphonates.

She is regularly followed to monitor disease status and treatment-related adverse events. By the end of November 2021, she was alive with stable disease.

This case shows a successful occipitocervical arthrodesis for cervical stabilization, and local disease control with radiation therapy in a middle-aged female with a solitary C1 plasmacytoma.


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Reports of Practical Oncology and Radiotherapy