PARATESTICULAR ANGIOSARCOMA FOLLOWING RADIATION THERAPY FOR PROSTATIC ADENOCARCINOMA
The most widely applied diagnostic criteria for radiation-associated sarcomas are adapted from Cahan's report of a sarcoma arising in irradiated bone1. These criteria can be summarized as a histologically proven neoplasm arising in the field of radiation with a latency period ranging from at least 3-5 years following radiation treatment. Our case fulfills these criteria, namely histologically proven angiosarcoma arising in paratesticular soft tissue 5 years after external beam radiation treatment for prostatic adenocarcinoma.
Radiation-associated angiosarcoma is a rare diagnosis. Risk estimates of post-irradiation sarcomas of any histologic subtype range 0.03 to 0.8%2,3. Studies generally agree that the largest proportion of radiation-associated sarcomas comprises of malignant fibrous histiocytomas and osteosarcomas, with angiosarcoma diagnosed less frequently. In a study of 37 patients with post-irradiation sarcoma, 13 cases (35%) were angiosarcomas; however, nearly half of these cases were secondary to radiation therapy for breast adenocarcinoma2. In a study of 53 cases of post-radiation soft tissue sarcomas at the Armed Forces Institute of Pathology, Laskin and colleagues4 found only one case of angiosarcoma arising in the chest wall 7 years following radiation therapy for mediastinal Hodgkin's disease. Two case-series from Memorial Sloan Kettering Cancer Center reported the prevalence of angiosarcoma/lymphangiosarcoma among radiation-associated sarcomas of soft tissue and/or bone to be 15%5,6.
Radiation therapy is a treatment option commonly employed in older male patients with prostatic adenocarcinoma7 with treatment efficacy that is similar to radical prostatectomy8. Brenner et al.9 demonstrated that radiation therapy for 51, 584 patients with prostatic carcinoma diagnosed between 1973-1993 was associated with a minute increase (6%) in the risk of any secondary malignancy in contrast to surgical treatment alone. This was attributed to an increased risk of bladder, lung, and rectal carcinomas and sarcomas in the field of radiation. The authors reported that the increased risk corresponds to 1 tumor in 125 men surviving > 5 years following radiation therapy, with a 6.5% risk that the tumor will be a sarcoma9. The risk of sarcoma outside the irradiation field was not increased by radiation therapy for prostatic carcinoma9.
To our knowledge, only two case reports of radiation-associated angiosarcoma following radiation therapy for prostatic adenocarcinoma have been published in the English literature. The first is a case of angiosarcoma arising in the bladder 13 years following radiation therapy for prostatic adenocarcinoma10. The second is a case of post-irradiation angiosarcoma of the prostate itself arising 10 years following irradiation11. Our case of paratesticular angiosarcoma arising 5 years following radiation therapy for prostatic adenocarcinoma represents the third reported case of post-irradiation angiosarcoma related to radiotherapy for prostate adenocarcinoma.
A recent study by Cha and colleagues6 examined the survival of patients with radiation-associated non-bony sarcomas. Their analysis revealed age >60 years, high-grade tumor histopathology and positive surgical resection margin status as negative prognostic factors for 5 year survival after the diagnosis of radiation-associated sarcoma6. Superficial radiation-associated sarcomas less than 5 cm in greatest dimension are at low risk for metastasis and are adequately treated by excision with negative margins3.
The recent literature suggests that there is a small risk of secondary sarcoma/angiosarcoma with radiation therapy for prostatic adenocarcinoma. This risk, albeit small, should be considered in follow-up evaluations of cancer patients who are status-post radiation therapy. Radiation-associated sarcoma should be included in the differential diagnosis of an enlarging mass in the field of radiation.
Contributed by Edward D. Plowey, MD, Jyoti P. Balani, MD, Uma N. M. Rao, MD and Rajiv Dhir, MD