Radiation-induced sarcoma presenting as a gluteal abscess: a diagnostic and therapeutic challenge

Discussion

Second malignancies are a devastating consequence of cancer treatment with ionising radiation. It was first described by Beck in the 1920s on a patient who developed sarcoma following radiation for benign conditions.2 The incidence of second malignancies is increasing because of the widespread administration of radiotherapy for cancers in recent years and the improved longevity of patients with cancer owing to advances in healthcare.

Sarcomas involving bone and soft tissues are the most common second malignancies occurring in patients with a history of radiotherapy. The most common types are osteosarcoma, fibrosarcoma, malignant fibrous histiocytoma and angiosarcoma. Cancers arising from breast, lung and stomach have also been described in patients who received radiotherapy for Hodgkin lymphoma.3 4

Cahan and Woodard postulated that RISs are lesions of different histology to that of non-irradiated sarcomas arising within a previously irradiated field with a latency period of minimum 4 years.5 The latency period following radiation exposure was modified by Arlen et al, who suggested that sarcomas can arise as early as 3 years following radiotherapy.6 Most studies have shown a longer period for the development of second cancer following initial radiotherapy, which ranges from 7 to 45 years with a mean of 16.8 years.7 Concurrent use of chemotherapy during radiation treatment has been shown to shorten the latency of the occurrence of RIS significantly.8

Our patient is a case of secondary high-grade pleomorphic gluteal sarcoma following radiotherapy for squamous carcinoma of the cervix which occurred after a latent period of 5 years.

Carcinoma of the cervix is a common malignancy in women, and radiation remains a mainstay in its treatment. It is found that survivors of carcinoma of the cervix have an 80% increased risk of developing a second malignancy when compared with the general population.9 Most reported cases of secondary sarcomas among patients treated for carcinoma cervix with radiation involved the pelvic bones. Moreira et al described a case of uterine carcinosarcoma, and Nakanishi et al reported five cases of pelvic bone sarcoma that developed following pelvic radiotherapy.2 10 Rare cases of pelvic RIS were also described following radiation treatment for rectal and prostate cancers.11 Our patient had a gluteal sarcoma which was an unusual location for RIS on cervical cancer survivors. It is found that RISs develop more commonly from the margins of the previously irradiated field where the initial radiotherapy was not sufficient enough to cause the cell death but is competent enough to cause genetic mutation, hence the occurrence of sarcomas at the sites mentioned above.

RISs are generally highly aggressive and exhibit a varied clinical spectrum. They seldom show any symptoms or signs in early stages and early diagnosis is rarely achieved. The symptom complex varies with the site of origin of secondary malignancy. Pelvic sarcomas usually present with a dull-aching pelvic pain and are commonly mistaken for skeletal metastases in pelvis bones. Bleeding can be presenting symptom in patients with sarcomas arising from vagina and rectum, manifesting as vaginal and rectal bleeding, respectively.12 13 Our patient presented with the classic clinical picture of gluteal abscess; thus, secondary gluteal sarcoma was not considered initially. These tissues are highly friable and are prone for profuse bleeding, significant life-threatening complication; this is evident in our patient where haemostasis was achieved only after radiation following failed attempts of surgical and radiological interventions.

MRI and CECT are the imaging modalities of choice to evaluate and follow RIS, which give us information about the local and distant spread of the disease.14 Imaging features are not pathognomonic and can be challenging to interpret. It is difficult to exclude a recurrence of the primary tumour by imaging alone. Thus, core needle biopsy remains the mainstay in the diagnosis. Biopsy not only helps in differentiating the new sarcoma from local recurrence, but it also enlightens on the histological subtype, grade of the sarcoma, postoperative and post-radiotherapy changes. Angiography can be used in patients who present with tumour bleed and can guide interventional procedures as in our case.

Radical resection with negative histological margins (R0) is the treatment of choice, though challenging because of distortion of anatomical and tumour planes due to radiotherapy. Chemotherapy is of limited benefit in these patients but is mainly used with palliative intent in patients with metastatic disease. Radiotherapy is not used in the management of RIS as the fields were previously irradiated, and providing radiotherapy would result in increased side effects in these patients. It can be used as a symptom control measure like achieving haemostasis as in our case.

The estimated 5-year survival of RIS varies between 17% and 58%. Most published studies state that the 5-year survival rate of RIS patients is significantly lower than that of patients with de novo soft tissue sarcoma.15 Positive surgical margin, microscopic tumour necrosis, metastases at the time of diagnosis and central location of the tumour are the various factors associated with more unsatisfactory outcome in patients with RIS.16