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Effect of screening by clinical breast examination on breast cancer incidence and mortality after 20 years: prospective, cluster randomised controlled trial in Mumbai

BMJ 2021; 372 doi: https://doi.org/10.1136/bmj.n256 (Published 24 February 2021) Cite this as: BMJ 2021;372:n256

Linked Opinion

The story of the Mumbai breast screening study

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Re: Effect of screening by clinical breast examination on breast cancer incidence and mortality after 20 years: prospective, cluster randomised controlled trial in Mumbai

Dear Editor

The results of the Mumbai breast cancer mortality study should be considered with caution.

Mittra et al. performed 3 tests to reach their conclusion (the test planned in the protocol on all women regardless of age and the 2 post-hoc tests for women younger than 50 and women aged 50 and older). As a result, the significance threshold should have been adjusted due to these multiple tests. With 3 tests, a significance threshold of 0.0167 is required in order to keep the Type I error less than or equal to 0.05. With this adjusted threshold, the decrease in breast cancer mortality observed in the subgroup of women aged 50 and older is no longer statistically significant.

Further studies are therefore needed before concluding that screening by clinical breast examination is effective in reducing mortality from breast cancer.

Competing interests: No competing interests

03 March 2021
Vincent ROBERT
MD retired
Rombas, France