Case Report of Abdominal Recurrence of Osteosarcoma

Osteosarcoma is the second most common primary tumor of the skeletal system and the most common primary bone malignancy. Localized osteosarcomas are typically confined to the bone, with approximately 50% affecting the femur and 80% located near the knee (proximal tibia or distal femur). While pulmonary and osseous metastases are common, nonpulmonary, non-osseous sites are rare and underreported. We present the case of a 41-year-old woman treated for localized distal femur osteosarcoma who developed both local and abdominal recurrence 18 months posttreatment. The abdominal mass, located in the duodeno-pancreatic region, responded favorably to palliative chemotherapy.

Introduction

Osteosarcoma is the most common primary malignant bone tumor, typically arising in the metaphysis of long bones [1], [2]. Its metastatic spread predominantly targets the lungs and, less frequently, the skeleton. Rarely, extrapulmonary and extraosseous metastases, such as those involving the abdomen, have been reported. These atypical metastases are often linked to advanced disease and poor prognosis. However, timely diagnosis and appropriate management may improve outcomes [3]. We report a rare case of abdominal metastasis from osteosarcoma and provide a review of the literature.

Case Presentation

A 41-year-old woman with no significant medical history was diagnosed in 2021 with a localized osteosarcoma of the distal right femur. Initial treatment included neoadjuvant chemotherapy: two cycles of API (doxorubicin, cisplatin, ifosfamide) alternating with two cycles of AI (doxorubicin, ifosfamide), followed by surgical amputation. Histopathological evaluation revealed a favorable response (Huvos Grade IV). She subsequently received three cycles of adjuvant API chemotherapy and was followed up regularly.

Eighteen months later, the patient presented with local and abdominal recurrence. Imaging revealed:

• MRI of the right thigh: A recurrent lesion in the diaphysis of the right femur (26 × 22 mm, extending 75 mm vertically), with soft tissue infiltration.

• Thoraco-abdomino-pelvic CT: A 41 × 43 mm mass in the region of the pancreatic head, suggestive of metastasis.

Biopsy of the stump confirmed recurrent dedifferentiated osteosarcoma. Endoscopic ultrasound (EUS) revealed a 4 cm paraduodenal mass abutting the pancreas and antrum. Histopathological analysis of the biliopancreatic mass showed spindle-shaped atypical cells consistent with metastatic osteosarcoma.

The patient began palliative chemotherapy with ifosfamide and etoposide. After three cycles, imaging showed:

• A 20% reduction in the size of the femoral tumor on MRI.

• A decrease in the size of the abdominal mass (75 × 67 mm vs. 96 × 91 mm) on CT.

• No evidence of pulmonary metastases.

These findings supported continuation of the current treatment.

Discussion

Primary osteosarcoma is a highly aggressive malignancy with a predilection for metastasizing primarily to the lungs and secondarily to the bones. Although nonpulmonary, nonosseous metastases have been documented, their rarity has limited the ability to systematically study these occurrences [3]. Advances in multiagent cytotoxic chemotherapy since the 1970s have significantly improved the 5-year survival rate for localized, nonmetastatic osteosarcoma from 15% to 67% [4]–[7]. However, longer patient survival has also revealed new, significant extrapulmonary metastatic sites, including the abdomen [8].

In our case, the patient was initially treated for localized osteosarcoma but developed an abdominal recurrence 18 months after completing adjuvant chemotherapy. The treatment protocol used for our patient consisted of ifosfamide and etoposide, which are commonly employed in such scenarios. Treatment decisions often consider factors such as prior disease-free survival and previously administered chemotherapy regimens. Additional options may include cyclophosphamide, etoposide, carboplatin [III, B], or other active agents like gemcitabine and docetaxel [IV, C] [9].

The occurrence of abdominal metastases in osteosarcoma is typically associated with a poor prognosis, with survival rarely extending beyond 2 to 3 years [3]. Remarkably, our patient remains alive and is responding well clinically and radiologically after three months of treatment, allowing continuation of the chemotherapy protocol.

Surveillance plays a critical role in the management of osteosarcoma, especially for detecting early recurrences, whether local or metastatic, including rare sites like the abdomen. Regular monitoring enables timely therapeutic adjustments, maximizing disease control and improving patient outcomes. Multimodal imaging techniques such as MRI, CT, and PET-CT, as recommended by the NCCN [10], are essential for restaging and tracking disease progression. In this case, the patient’s surveillance allowed for the prompt detection of abdominal metastases and evaluation of treatment response, leading to tailored chemotherapy protocols and better palliative care.

Osteosarcoma is a highly aggressive malignant bone tumor that most frequently metastasizes to the lungs, followed by secondary skeletal involvement. While non-pulmonary, non-osseous metastases have been described, such occurrences are exceedingly rare and often underreported in the literature, limiting comprehensive analysis [3]. However, as survival outcomes improve due to the advent of multiagent chemotherapy, new metastatic patterns—such as abdominal involvement—are being increasingly recognized [8].

In this case, our patient developed an abdominal recurrence 18 months after completing treatment for localized osteosarcoma. This timeline and metastatic pattern are consistent with the findings of Serpico et al., who reported two similar cases of abdominal metastases arising during post-treatment follow-up, emphasizing the need for broader surveillance strategies [3]. Other published case reports, such as Yu and Yao’s, have also identified extrapulmonary metastases to visceral organs including the liver and kidneys, underlining the variability of metastatic behavior in osteosarcoma [8].

Our patient responded favorably to palliative chemotherapy combining ifosfamide and etoposide. This regimen is a commonly utilized second-line option, especially when prior chemotherapy regimens include agents like doxorubicin and cisplatin. Alternative regimens cited in the ESMO–EURACAN–GENTURIS–ERN PaedCan guidelines include carboplatin-etoposide and gemcitabine-docetaxel combinations, particularly in patients with prolonged disease-free intervals or limited treatment options [9].

The prognosis of osteosarcoma patients with abdominal metastases remains poor, with median survival rarely exceeding two to three years [3]. Nonetheless, early detection and tailored treatment—as seen in our case—can improve symptom control and potentially prolong survival. Our patient showed notable clinical and radiologic improvement after three cycles of chemotherapy, which is encouraging and supports the continuation of the same regimen.

Vigilant surveillance plays a pivotal role in managing osteosarcoma. Multimodal imaging tools such as MRI, CT, and PET-CT—as endorsed by the NCCN—are essential for detecting early signs of recurrence, including those at atypical metastatic sites [10]. In our case, timely imaging allowed prompt diagnosis of abdominal recurrence and initiation of effective palliative treatment.