Long-term risk of sarcoma following radiation treatment for breast cancer

Between 1954 and 1983, 7620 patients were treated for breast carcinoma at Institut Gustave Roussy (France). Of these patients, 6919 were followed for at least 1 year. Out of these, 11 presented with sarcomas thought to be induced by irradiation, 2 of which were Steward-Treves Syndrome, and 9 of which were sarcomas within the irradiated fields. All histological slides were reviewed and a comparison with those of breast cancer was done. The sites of these sarcomas were: parietal wall, 1 case; second costal cartilage, 1 case; infraclavicular region, 1 case; supraclavicular region, 2 cases; internal third of the clavicle, 2 cases; axillary region 2 cases; and the internal side of the upper arm (Stewart-Treves syndrome), 2 cases. The median age of these 11 patients at the diagnosis of sarcomas was 65.8 (49-83). The mean latent period was 9.5 years (4-24). Three patients underwent radical mastectomy and nine modified radical mastectomy. Only one patient received chemotherapy. The radiation doses received at the site of the sarcoma were 45 Gy/18 fr. for 10 cases and 90-100 Gy for 1 case (due to overlapping between two fields). The histology was as follows: malignant fibrous histiocytoma, 5 cases; fibrosarcoma, 3 cases; lymphangiosarcoma, 2 cases; and osteochondrosarcoma, 1 case. The median survival following diagnosis of sarcoma was 2.4 years (4 months- 9 years). Two patients are still alive: one with recurrence of her breast cancer, the other in complete remission, with 7 and 3 years follow-up, respectively. All other patients died from their sarcomas. The cumulative incidence of sarcoma following irradiation of breast cancer was 0.2% (0.09-0.47) at 10 years. The standardized incidence ratio (SIR) of sarcoma (observed n# of cases (Obs)/expected n# of cases (Exp) computed from the Danish Cancer Registry for the same period) was 1.81 (CI 0.91-3.23). This is significantly higher than one, with a p = 0.03 (One Tailed Exact Test). The mean annual excess (Obs-Exp)/100.000 person-years at risk during the same period/(100 000) was 9.92. This study suggests that patients treated by radiation for breast cancer have a risk of subsequent sarcomas that is higher than the general population. However, the benefit from adjuvant radiation therapy in the treatment of breast cancer exceeds the risk of second cancer; therefore, the potential of radiation-induced sarcomas should not be a factor in the selection of treatment for patients with breast cancer.