- Cancer of the cervix is the cause of death in 2.3 of every 100,000 white women annually in the United States.
- For breast cancer, the death rate in the same population is, comparatively, more than 10-fold: 24.4 of every 100,000 women.
Those numbers, from the American Cancer Society, immediately raise a question for me: Why is the rate of death from cervical cancer so low in comparison to what’s been reported for breast cancer?
The answer, in part, is that ObGyns and other clinicians have worked hard to implement effective cervical cancer prevention and screening programs and have treated preinvasive precursor lesions aggressively. ObGyns have led the way in reducing death from cervical cancer.
My second question, then, is: As guardians of women’s health, can’t ObGyns be doing more than we are to reduce the rate of death from breast cancer?
Here are some observations, gathered from a look at the scientific literature, on what we can do to make a difference, and where we remain stymied, in the battle against breast cancer.
A lack of “molecular intelligence” puts us at a disadvantage
Harald zur Hausen was co-awarded the Nobel Prize in Physiology or Medicine in 2008 for discovering the role of human papillomavirus (HPV) in cervical cancer. Thanks to his work, and that of his colleagues and other researchers, the molecular mechanisms that give rise to cervical cancer are reasonably well understood: When oncogenic types of HPV integrate into the genome of cervical cells, that integration prompts expression of two viral proteins: E6, which binds to p53, and E7, which binds to retinoblastoma protein (Rb)—leading to an increase in cell proliferation and oncogenesis.
Understanding the basic biology of cervical cancer has helped us design prevention, screening, and treatment strategies that work.
In contrast, the molecular mechanisms that cause breast cancer aren’t understood. Men rarely get breast cancer, however, so we can deduce that female reproductive hormones, including estradiol and progesterone, probably play an important role in the pathogenesis of breast cancer.
Reproductive risk factors are well-established
Epidemiologic studies show that the risk of breast cancer is increased by:
- early menarche
- late menopause
- late age at first birth
- obesity in postmenopausal women.
Conversely, breastfeeding and exercise reduce the risk of breast cancer.
The evidence suggests, therefore, that you should counsel your patients to:
- exercise regularly
- breastfeed their newborn
- maintain normal body mass.
The value of examination
Mammography and the clinical breast exam detect about 90% and 50% of breast cancers, respectively, in screening programs. In a prospective trial of more than 39,000 women who were 50 to 59 years old and followed for as long as 13 years, a standardized and thorough clinical breast exam was as effective as a breast exam plus mammography for detecting invasive breast cancer that caused death.1
Clinical breast exam. According to some experts, a thorough clinical breast exam requires at least 6 minutes of examination time. One recommended technique includes the following steps:
- flatten breast tissue against the chest
- examine the breast in vertical strips
- use three different degrees of pressure to examine the breast
- examine each breast for at least 3 minutes.2
Breast self-exam hasn’t been demonstrated to effectively detect breast cancer, but it does increase the rate at which women detect benign breast lesions.3 It may be that breast self-examination, as taught today, is insufficiently thorough to detect breast cancer.
Screening technology: Use it properly
Mammography. For women older than 50 years, annual mammography reduces mortality from breast cancer by approximately 35%.4 For women who are 40 to 50 years old, annual or semiannual mammography reduces mortality from breast cancer by about 15%.5 In my practice, I recommend that all women older than 40 years have a mammogram annually.
Magnetic resonance imaging of the breast is much more expensive than mammography. It requires a contrast agent, such as gadolinium, which can cause nephrogenic systemic fibrosis.
MRI of the breast is more sensitive, but less specific, than mammography.
The American Cancer Society cautions against using MRI as part of a screening algorithm for breast cancer unless the woman’s lifetime risk of breast cancer is greater than 20% to 25%.6 This level of risk is found most often in women who have a BRCA mutation; who have had chest irradiation (for example, for lymphoma); and who have a strong family history of breast cancer.
Some women benefit from chemoprevention
The Gail model. Women who are at high risk of breast cancer may benefit from hormonal chemoprevention with a selective estrogen receptor modulator (SERM). The Gail model is the most widely used tool for assessing such risk.