Adjuvant volumetric modulated arc therapy for incompletely resected type II pleuropulmonary blastoma: a case report

Abstract

Background: Pleuropulmonary blastoma (PPB) is a rare and aggressive pediatric thoracic malignancy within the DICER1 syndrome spectrum. Despite well-established multimodal treatment based on surgery and chemotherapy, evidence guiding the use of adjuvant radiotherapy remains scarce, given the rarity of this tumor. Case report: A 3-year-old girl with type II PPB, presenting with recurrent pyopneumothorax, achieved a 76% tumor reduction after seven cycles of IVADo chemotherapy, allowing incomplete surgical resection with residual viable tumor. Adjuvant VMAT (45 Gy/25 fractions) achieved excellent target coverage with organ sparing and was well tolerated (grade 2 radiodermatitis only), and the patient remained disease-free at 9 months. Conclusion: This case highlights the feasibility of modern VMAT-based adjuvant radiotherapy for incompletely resected type II PPB and illustrates how advanced treatment planning can optimize local control while limiting radiation exposure to critical organs.

Introduction

Pleuropulmonary blastoma (PPB) is a rare and highly aggressive embryonal malignancy of the lung parenchyma and pleura, associated with the DICER1 syndrome occurring almost exclusively in children younger than six years of age [1]. Giving its rarity (estimated incidence of 0.35–0.65 cases per 100 000 live births), therapeutic recommendations rely mainly on registry data and expert consensus rather than clinical trials. Complete surgical removal of the tumor represents a major determinant of prognosis and may be performed upfront or after neoadjuvant therapy, which generally consists of chemotherapy and, in certain situations, radiotherapy [2].

In this report, we describe the feasibility, dosimetric characteristics, acute toxicity, and early clinical outcomes of adjuvant volumetric modulated arc therapy (VMAT) in a child with incompletely resected type II PPB.

Case report

We report the case of a 3-year-old girl with a one-month history of weight loss, fatigue, fever and cough. On admission, chest radiography revealed a left-sided pyopneumothorax requiring chest tube drainage (Fig. 1). Following recurrence, chest CT confirmed a persistently large, left-sided pyopneumothorax (Fig. 2).

Figure 1.

Frontal chest radiograph of a pediatric patient showing a left-sided pyopneumothorax with an air-fluid level, indicated by an arrow.

Figure 2.

Axial CT scan of the chest showing a large left pyothorax with air bubbles causing subtotal pulmonary collapse, with a few basal linear bands of right atelectasis, indicated by an arrow.

Thoracoscopy with biopsy revealed, one week later, a pleural effusion, a collapsed left lung adherent to the pleura, and a mass with a tumoral appearance.

Three weeks after admission, histopathological examination showed a mixed cystic and solid tumor with blastematous and sarcomatous differentiation, marked atypia, and extensive necrosis, confirming a type II pleuropulmonary blastoma.

Germline DICER1 testing was recommended but could not be performed because of financial limitations, limiting surveillance for associated neoplasms and familial genetic counseling. Staging investigations, including bone scintigraphy and brain MRI, demonstrated no evidence of metastatic disease. The patient received seven cycles of neoadjuvant IVADo chemotherapy (ifosfamide, vincristine, actinomycin D, and doxorubicin) over approximately five months, starting shortly after histological confirmation. According to RECIST version 1.1 criteria, tumor assessment showed a 55% reduction after the third cycle and a 76% reduction after completion of chemotherapy, consistent with a partial response (Fig. 3). Approximately one week after completion of chemotherapy, she underwent a left posterolateral thoracotomy with en bloc resection of a non-encapsulated left lower lobe tumor involving the parietal pleura, diaphragm, and adjacent lung. Complete resection was not achieved because of persistent infiltrative disease. Histopathological examination confirmed residual viable pleuropulmonary blastoma with marked post-chemotherapy changes (approximately 88%). Surgical margins could not be assessed because of the fragmented specimen. Therefore, adjuvant radiotherapy was indicated in accordance with the current EXPeRT recommendations [3].

Figure 3.

Axial CT scans of the chest in four panels showing progressive regression of a left pleural mass during chemotherapy: panels A show a 55% size reduction after the third cycle, and panels B show a further 76% reduction after the sixth cycle, both with arrows indicating the residual mass.

CT simulation was performed nine days after surgery with the patient in the supine position using a pediatric vacuum immobilization device. General anesthesia was not required because the child remained cooperative throughout the treatment. Considering the patient’s young age and previous exposure to anthracyclines, a total dose of 45 Gy in 25 fractions (1.8 Gy per fraction, five fractions per week over five weeks) was prescribed to optimize local control while limiting late toxicity. The clinical target volume (CTV) encompassed the post-chemotherapy and pre-surgical tumor volumes, including the adjacent pleura when involved. A planning target volume (PTV) margin of 1 cm was added to account for setup uncertainties and respiratory motion (Fig. 4).

Figure 4.

Four-panel radiation therapy planning image showing axial, coronal, and sagittal CT views with color-coded isodose lines around the tumor volume, alongside a dose-volume histogram showing the percentage of organ volumes receiving each radiation dose.

Treatment was delivered using dual-arc VMAT with 6 MV flattening filter-free photon beams. The dosimetric parameters of the treatment plan are summarized in Table 1 [4].

Table 1.

Dosimetric parameters of the treatment plan.

Structure	Dosimetric parameter	Value
Planning Target Volume (PTV)	RTOG Conformity Index (CI)	1.10
	ICRU 83 Homogeneity Index (HI)	0.13
Ipsilateral lung (left)	Mean dose	12,99 Gy
	V20	14,42%
Contralateral lung (right)	Mean dose	9 Gy
Heart	Mean dose	8,81 Gy
Spinal cord	D 0,03 m3	20,56 Gy
Vertebral body	Mean dose	23 Gy
Liver	D100%	10 Gy

No acute toxicities were observed, except for a grade II radiodermatitis (Fig. 5), which resolved within four months after the completion of radiotherapy.

Figure 5.

Clinical photograph of the skin overlying the treatment field showing grade II radiodermatitis, characterized by erythema and patchy desquamation.

At 9 months follow-up, the patient remained clinically well with no evidence of local recurrence, distant metastasis, or late radiation-induced toxicity.

Discussion

PPB is a dysembryoplastic disease classified into three progressive subtypes with distinct prognostic implications: Type I (cystic), Type II (mixed solid-cystic), and Type III (solid) [5].

The clinical presentation is often nonspecific and may mimic common respiratory conditions. Multimodal treatment has significantly improved survival rates, with reported cure rates exceeding 70% for type II disease. Complete surgical excision remains the most important determinant of outcome [6].

Resection may range from wedge resection to pneumonectomy depending on disease extent, though large tumors are often difficult to resect with negative margins, and pneumonectomy carries a risk of post-pneumonectomy syndrome [1].

Consequently, neoadjuvant chemotherapy has become an important component of treatment for locally advanced PPB [7]. In the present case, IVADo chemotherapy induced substantial tumor regression, facilitating subsequent surgery, although complete resection was not achieved.

The role of radiotherapy in PPB remains controversial because of the rarity of the disease and the absence of randomized studies. Early series and registry-based studies reported conflicting results, with Williams et al. finding no survival benefit from radiotherapy in type II/III PPB [8, 9], whereas the EXPeRT study and the larger Schultz et al. registry analysis both showed improved survival with radiotherapy in patients with residual disease [7, 10].

The current EXPeRT/PARTNER recommendations therefore advocate postoperative radiotherapy for patients with microscopic or macroscopic residual disease, incomplete resection, pleural dissemination, or recurrent disease. Recommended doses generally range from 45 Gy for microscopic residual disease to 54 Gy for gross residual disease [3].

In the present case, postoperative radiotherapy was individualized according to the patient’s age, prior anthracycline exposure, and the risk of late toxicity. Following multidisciplinary discussion and in accordance with the EXPeRT/PARTNER recommendations, a lung-preserving approach with postoperative VMAT delivering 45 Gy in 25 fractions was selected to optimize local control while minimizing long-term treatment-related toxicity. Delineating the CTV on the post-chemotherapy rather than initial tumor volume minimized irradiation of healthy lung tissue. Although proton therapy could potentially further reduce the integral dose, it is currently unavailable at our institution. Dosimetric results demonstrated satisfactory target coverage while maintaining the heart and lung doses within the accepted pediatric tolerance levels.

Finally, the 9-month follow-up remains too short to confirm durable local control or exclude late radiation-induced toxicity, particularly in a child of this age; longer-term surveillance is warranted.

Conclusion

This case demonstrates the feasibility and safety of adjuvant VMAT for incompletely resected type II pleuropulmonary blastomas. Postoperative radiotherapy achieved early local control with minimal acute toxicity, supporting its role in the multimodal management of selected patients.

Conflicts of interest

The authors declare no conflict of interest.

Funding

This study did not receive any external funding.

Ethical approval

Ethics committee approval was not required for this case report in accordance with the institutional policy of the National Institute of Oncology, Rabat, Morocco.

Informed consent

Written informed consent was signed by the patient’s legal guardian, granting approval for the publication of this clinical case, including the accompanying radiological images and the photograph of the treatment-related side effect, in the hope that this report may help other physicians facing this rare condition.

Guarantor

Dr. Salma Ichou accepts full responsibility for the integrity of the work as a whole, from inception to the published article.