A substantial proportion of women with cervical cancer that have participated in cervical screening have a history of an abnormal cytology result. Our objective was to assess the impact of histological investigation and treatment of women with abnormal cytology on the subsequent risk of invasive cervical cancer. All invasive cervical cancer cases in Sweden 1999-2001 and five population-based control women per case were investigated. Clinical investigations and treatment were analysed in case women (N = 143) and control women (N = 176) below 67 with abnormal cytology results 0.5-6.5 years before the cases' diagnosis. Cervical cancer risk in relation to investigation [histology or not, punch biopsy, cervical curettage or cone/large loop excision of the transformation zone (LLETZ)], and treatment (treatment or not, excisional or ablative) was estimated as odds ratios (ORs) using logistic regression. Absence of histological assessment was associated with increased cancer risk, both after low-grade [OR 2.37; 95% confidence intervals (CI): 1.27-4.43] and high-grade squamous atypia (8.26; 2.37-28.8). Among women with histology, absence of treatment was associated with increased cancer risk (3.68; 1.53-8.84), also when biopsy showed low-grade atypia or normal findings (3.57; 1.18-10.8). Ablative therapy associated with increased risk compared with excisional (3.82; 1.01-14.4), and laser conisation associated with decreased risk compared with LLETZ (0.06; 0.01-0.36). In conclusion, low-grade as well as high-grade squamous atypical cytology results may warrant histological investigation, treatment reduced cancer risk even when histology was negative or showed low-grade atypia indicating a need for improvements in the diagnosis of high-grade lesions, and laser conisation was the most effective treatment.
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