Second primary malignancies among women with uterine sarcoma

Objective: Uterine sarcomas (US) are rare malignancies with unclear aetiology. Studies on uterine sarcomas in the setting of second primary malignant tumours can provide clues to aetiology and identify side effects of different treatments.

Methods: A cohort of 8606 cases of US was extracted from the data from 13 cancer registries and followed for second primary cancers within the period 1943-2000. Standardized incidence ratios (SIRs) were calculated, and Poisson regression analyses were performed.

Results: There were 499 cancer cases observed after a first diagnosis of US (SIR 1.26, 95%CI 1.16-1.38). SIRs were elevated for cancers of the mouth and pharynx (2.16, 95%CI 1.15-3.69), colorectum (1.60, 95%CI 1.28-1.98), lung (1.73, 95%CI 1.27-2.29), breast (1.25, 95%CI 1.05-1.49), urinary bladder (1.74, 95%CI 1.02-2.79), kidney (2.00, 95%CI 1. 24-3.06), thyroid gland (2.74, 95%CI 1.42-4.79), and soft tissue sarcoma (5.23, 95%CI 2.51-9.62). The risk of breast cancer increased along with increasing age of US diagnosis (p trend 0.040). The risk of kidney cancer increased along with decreasing age of US diagnosis (p trend 0.004) and short time since the US diagnosis (p trend 0.018).

Conclusions: Our study demonstrated increased risk of certain cancers following a diagnosis of US. The elevated risk for breast cancer may indicate shared hormonal aetiology, while the increased risk of colorectal and bladder cancers after US may be caused by radiation therapy of US. The clustering of smoking-related cancers after US is worth exploring in the future.