The 4th workshop of the UICC project on screening for cancer was held in Helsinki, Finland on April 7-9, 1986.
In developed countries there are more data available from controlled trials on the effectiveness of screening for breast cancer than for any other cancer. Nevertheless, full information is not available on every issue, and indeed interpretation of some of the available data is controversial.
Review of available study 1. Zhe HIP study
The most recent results covering 18 years of follow-up were presented for the New York Health Insurance Plan (HIP) Study. The study and control groups were very similar with respect to overall mortality and breast cancer incidence. However, within the study group, there were differences between acceptors and rejectors, with the latter showing higher overall mortality and lower rates of breast cancer incidence. At 5 years after entry into the study group, 74% of cancers were found in the ever-screened group and 26% in the refusers. Cancers picked up at screening were more likely to be node-negative. Case survival rates show an advantage for mammography-detected cases even over a long period of time. Breast cancer mortality was lower in the study group than in the control group at 5 years, and at 18 years the differential persisted, study group mortality being 23 % less than that of the control group.
Case survival rates reflect a similar beneficial effect for the study group. There was only a small difference between the control and study node-negative cases with respect to cumulative survival by the end of the followup period. A larger difference existed between the two groups for node-positive disease. In terms of the proportion node-negative at diagnosis, women in the 40-49 age-group did not benefit as much as older women.
After 18 years of follow-up, proportional reduction in mortality for the study group was observed for each quinquennium of age at entry between ages 40 and 64. However, the difference did not begin to appear until after 8 years post-entry for women aged 40 to 44 at entry and after 5.5 years for women aged 45 to 49, while for women aged 50-59, the effect began at 3 years. In terms of person/years of life lost, the advantage at 18 years post-entry for women aged 40-49 was substantially lower than for women aged 50 and over. The mortality reduction among women aged 4049 on entry did not achieve statistical significance. Estimated lead time achieved by screening was greater for women aged 50-59 (21.9 months k 5.9) than for those aged 40-49 at entry (5.2 months & 9.6).
It was concluded that, according to HIP data, screening does reduce breast cancer deaths. The gain achieved in women aged 40 to 49 is still open to question.