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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

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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
In the past two decades, several trials have concluded that breast cancer screening for women between the ages of 50 and 69 years can reduce the rate of death from breast cancer by approximately 25% (1). Nevertheless, the role of mammography and other screening tools in breast cancer are still debated, chiefly because of concern regarding methodologic and procedural drawbacks of most randomized trials.

In this context, Mittra et al need to be complimented for doing a prospective, randomized controlled trial on the effect of screening by clinical breast examination (CBE) on breast cancer incidence and mortality(2). In the context of developing nations, the trial brings forth crucial in-house evidence related to an increasing health problem. This is further so, since this trial investigates and presents a cheap and readily available means for breast cancer screening.

However, some of the findings of the study need further introspection. A 30% reduction in mortality in women > 50 years is a promising outcome of the study. Why the strategy of CBE combined with awareness worked well only for women > 50 years needs further answers. Akin to mammography, it is possible that as the suppleness of breast increases with age, the sensitivity/specificity of CBE increases as well (3) ? In the same vein, women < 50 years of age who attended all four rounds of screening benefitted significantly from mortality reduction, likely because younger women risked a higher chance of getting the lump missed in CBE, if subjected to fewer rounds(4).

The increase in breast cancer mortality in the early years of screening has always been a controversial topic and has once again been brought up by this study. There is some evidence that connects increased CTC’s to the process of surgery (5). Is it the act of detection of cancer or an act of surgery that is leading to this increase in mortality? This is a question that begs answers in appropriately designed trials in future.

References
1. Duffy SW, Vulkan D, Cuckle H, Parmar D, Sheikh S, Smith RA, Evans A, Blyuss O, Johns L, Ellis IO, Myles J, Sasieni PD, Moss SM. Effect of mammographic screening from age 40 years on breast cancer mortality (UK Age trial): final results of a randomised, controlled trial. Lancet Oncol. 2020 ;21:1165-1172
2. Mittra I, Mishra GA, Dikshit RP, Gupta S, Kulkarni VY, Shaikh HKA et al 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 Feb 24;372:n256.
3. Kerlikowske K, Grady D, Barclay J, Sickles EA, Ernster V. Effect of age, breast density, and family history on the sensitivity of first screening mammography. JAMA. 1996;276:33-8
4. Chen TH, Yen AM, Fann JC, Gordon P, Chen SL, Chiu SY et al Clarifying the debate on population-based screening for breast cancer with mammography: A systematic review of randomized controlled trials on mammography with Bayesian meta-analysis and causal model. Medicine (Baltimore). 2017;96:e5684
5. Li, S., Yan, W., Yang, X. Chen L, Fan L, Liu HKun Liu, Less micrometastatic risk related to circulating tumor cells after endoscopic breast cancer surgery compared to open surgery. BMC Cancer 2019;19:1070

Competing interests: No competing interests

04 March 2021
ANUSHEEL MUNSHI
RADIATION ONCOLOGIST
MANIPAL HOSPITAL, DWARKA, NEW DELHI, INDIA
MANIPAL HOSPITAL, DWARKA, NEW DELHI, INDIA