medwireNews: Breast cancer screening by clinical breast examination (CBE) is a viable approach in low and middle income countries, suggests an Indian cluster randomized controlled trial (RCT).
“We showed that biennial CBE performed by trained female primary health workers significantly advanced breast cancer diagnosis by 16 months, and also downstaged the disease with fewer stage III or IV cancers in screened women,” write the investigators in The BMJ.
They continue: “Our study suggests that implementation of population screening by CBE in low and middle income countries is feasible, provided that adequate training of screening providers, careful monitoring, and quality of performance are assured.”
The team explains that “[m]ammography, which is widely practiced in Western countries, might not be an appropriate approach in low and middle income countries because of its cost and complexity,” whereas “[b]reast self-examination might not be useful as a general strategy, largely because it is not feasible to ensure women perform it well.”
Indraneel Mittra and co-workers from the Tata Memorial Centre in Mumbai, India, therefore evaluated the efficacy of CBE-based screening in a cluster RCT involving 151,538 women aged 35–64 years from 20 geographically distinct locations in Mumbai. The screening group received four rounds of CBE by trained female primary healthcare workers and cancer awareness education every 2 years, followed by five rounds of active surveillance every 2 years, while the control arm received one round of cancer awareness education followed by eight rounds of active surveillance every 2 years.
The average age at breast cancer diagnosis was significantly younger in the screening than control arm, at 55.18 and 56.50 years, respectively, and the proportion of women with stage III or IV disease at diagnosis was significantly lower, at 37% versus 47%.
The downstaging results were similar when participants were stratified by age; among women younger than 50 years, stage III–IV breast cancers were diagnosed in 37% of those who underwent CBE-based screening and 47% of those who did not, while the corresponding proportions were 35% and 46% among those aged at least 50 years.
Overall, the crude rate of breast cancer deaths over the 20-year study period was 20.82 per 100,000 person–years in the screening group and was 24.62 per 100,000 person–years in the control group. This equated to a 15% reduction in the mortality risk with screening, albeit without reaching statistical significance.
However, stratification by age group showed that screening was associated with a significant 29% reduction in the risk for breast cancer mortality among women aged 50 years or older, with crude incidence rates of 24.62 versus 34.68 per 100,000 person–years in the screening and control groups, respectively. But there was no significant decrease in the risk among women younger than 50 years.
This “[l]ack of mortality reduction in younger women is consistent with data reported in some mammography trials, and could point to undetermined biological factors,” say the researchers.
They also note that the number of screening rounds attended appeared to be crucial in the younger age group, such that women who attended all four rounds of screening had a significant 34% decrease in breast cancer mortality risk, whereas no such benefit was observed for those who only attended three rounds.
The team highlights, however, that the subset analyses based on the 50-year threshold were not stipulated in the protocol and are therefore exploratory in nature.
Finally, there was a nonsignificant 5% reduction in all-cause mortality in the screening versus the control arm, but Mittra and colleagues note that “because breast cancer deaths comprise less than 3% of all deaths in women in India, we did not expect a reduction in all cause mortality in our study.”
They conclude that the success of CBE-based screening with regard to reductions in mortality “can only be ascertained several years after CBE has been implemented as [a] public health programme.”
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