A Case of Complete Abscopal Response in High-Grade Pleiomorphic Sarcoma Treated with Radiotherapy Alone

Abstract

Background: "Abscopal response" refers to the spontaneous involution of untreated metastatic disease following local primary tumor-directed therapy. We report a case of an abscopal response of untreated lung metastasis in a man with pleomorphic sarcoma of the head and neck treated with hypofractionated radiotherapy.

Methods: An inoperable pleomorphic sarcoma of the postauricular soft tissue was treated with 40 Gy of radiation in eight fractions. Untreated disease in the lungs was followed with CT scans.

Results: At the two-month post-treatment follow-up, clinical exam and restaging CT demonstrated complete primary tumor involution. Additionally, CT chest images showed a dramatic disease response in the untreated pulmonary disease, which progressed to complete and persistent clinical response at one-year post-treatment follow-up.

Conclusions: We report the first described case of a complete abscopal resolution of untreated lung metastases in a patient with a primary pleomorphic sarcoma of the head and neck treated with hypofractionated radiotherapy.

Keywords: abscopal; head and neck cancer; radiotherapy; sarcoma.

Figure 1. Axial Post-Contrast CT Images of the Primary Tumor Before and after Two Months Post-Treatment

Axial post-contrast CT images of the primary tumor before (left, white arrow) and 2 months post treatment (right, white arrow). The involution in tumor size was so dramatic the radiology report was read as “status/post resection of the mass between the left sternocleidomastoid and parotid gland,” even though no surgery had been done. A representative image of the radiotherapy plan is also shown (center panel). 95% (A), 50% (B) and 30% (C) isodose lines are shown.

Figure 2. A Representative H+E Section of the Tumor Before Radiotherapy

A representative H+E section of the tumor before radiotherapy. The neoplastic cells are negative for S100, HMB 45, CD34, CD31 and CAM 5.2. The overall morphologic features and immunoprofile are consistent with high-grade undifferentiated pleomorphic sarcoma. No significant infiltration of lymphocytes or macrophages is noted.

Figure 3. A Representative Series of Images Demonstrating the Abscopal Response Noted in the Untreated Lung

Images shown are pretreatment (A) As well as post-treatment at two months (B) and four months (C). The other two lesions (not shown) showed a similar response, and all pulmonary disease had completely regressed at ten months follow-up.

Figure 4. Two Months Post-Treatment

At two months post-treatment, minimal skin changes over the treated site could be noticed. There were no subjective changes in hearing acuity or salivary gland function.