4/17 Early detection of breast cancer Flashcards
highest risk of death from a non-smoking woman?
breast cancer
good news about breast cancer?
breast cancer mortality has fallen 30% in the last 20 years
why has breast cancer mortality has fallen 30% in the last 20 years?
1) better treatment – breast cancer treatment has improved a lot over the last 20 years
2) earlier detection (mammography) – screening has little to do with the decline in breast cancer mortality; if it works at all the benefit is small
What treatments are available for breast cancer?
1) primary therapy: surgery
2) adjuvant therapy: radiation, chemotherapy, and hormonal therapy
the majority of breast cancers are of this type
ER (+); indicates that its relatively well-differentiated
As treatment gets more effective, screening becomes less effective and less important. Why?
Sweden and Norway: huge increase in breast cancer screening, but the mortality rates hasn’t decreased significantly. Mortality has declined in all places due to BETTER TREATMENTS (ie national screening programs for testicular cancers/pneumonia do not exist because there are good treatments for these)
Screening has little to do with the decline in breast cancer mortality; if it works at all the benefit is small. Why?
there is no debate about diagnostic mammography to determine what a breast lump is, but there is question of using the screening methodology on women without breast lumps to look for microscopic changes
major harms of screening?
false +’s
overdiagnosis
what are the problems of false +s on breast screening?
suspect that something is wrong but on a cellular level is normal; patients walks away thinking that they don’t have cancer or have significant anxiety levels because they may have some mild diagnosis but there is nothing being done about It; they may feel this way up to 3 years out
what are the problems of overdiagnosis on breast screening?
may have some cellular abnormalities that may never progress to something that is pathologic; patient walks away thinking that they’re diagnosed with cancer and that nothing is being done about it.
how do you know overdiagnosis occurs?
often inferred from other data/randomized trial screenings
Malmo RCT of screening mammography found that there were 741 patients who underwent mammography and 626 patients who did not undergo mammography who developed breast cancer.
Overtime, of the 150, there were 35 cancers in the non-screening group that “caught up”, resulting in while the rest did not, indicating that they were over-diagnosed cancers.
over-diagnosed cancers occur via screening, routine breast exam (woman comes in with a lump in her breast and gets a mammography)
advancing the time of diagnosis without changing the outcome
lead time
2 prereqs in order for screening to lower cancer mortality
1) early treatment of cancer destined to cause death must confer some advantage over late treatment
2) screening must advance the time of diagnosis of cancers destined to case death early; ideally
if you screen the population, the expected effect on the rate of early-stage disease detection should
if you screen the population, the expected effect on the rate of late-stage disease detection should
Does this actually occur in real life?
increase
decrease (thinking that you’re moving patients from the late stage to the early stage (earlier detecting) but doesn’t change the overall incidence of cancer)
following the introduction of screening mammography in women age 40yo or older, the # of women diagnosed with early-stage breast cancer nearly doubled. However, the was little compensatory decrease in the number of women presenting with late-stage breast cancer
there has been little change in the rate of breast cancer among women under age 40, suggesting that there has not been a dramatic change in the underlying amount of breast cancer.
if you screen the population, the expected effect on the rate of late-stage disease detection should
decrease (thinking that you’re moving patients from the late stage to the early stage (earlier detecting) but doesn’t change the overall incidence of cancer)
