After excluding the first year of follow-up, a decreasing trend in SIR with increasing time since first primary CRC was found for all cancers (SIR 1,18; 95% CI 1.07–1.30; SIR 0.88; 95% CI 0.80–0.95; SIR 0.82; 95% CI 0.75–0.89 for 1–4, 5–9 and 10 or more years since first primary, respectively; p -trend < 0.001), A decreasing trend in SIR was also found for lung cancer ( p < 0.001), stomach cancer ( p = 0.001), ovarian cancer ( p = 0.003), CRC ( p = 0.003), liver cancer ( p = 0.004), kidney cancer ( p = 0.01) and bladder cancer ( p = 0.04).
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The overall higher SIR was, nevertheless, due to few specific cancer types, including ovary, kidney, endometrial and bladder cancer, and stomach cancer with borderline significant increase.
When looking at Table 4 , however, some exceptions can be noticed: breast and prostate cancer showed no trend, consistent with the fact that they did not turn out to be associated to CRC as FPC; thyroid cancer also lacks a significant trend, likely due to the small number of cases included in the study; endometrial cancer was the only cancer type which showed to be at an increased risk with a constant trend in time.