Cancer Prevention and Control.Indd
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COMMENTARY Cancer Prevention and Control Then and Now Patricia A. Ganz, UCLA Jonsson Comprehensive Cancer Center October 22, 2018 Controlling or reducing the risk for cancer was a prin- obstruction of the drainage system from the kidneys. cipal goal of the National Cancer Act, signed by Presi- While radical hysterectomy is still performed today, dent Nixon in 1971. Long before the human genome the exenteration surgical procedure was abandoned was sequenced, and the etiology of many cancers was due to its extreme morbidity and failure to prevent understood, Americans were determined to fi nd a way both local and distant metastatic disease. to reduce the burden of cancer in the population. The Today, we understand that almost all cervical cancer act was passed only seven years after the fi rst US Sur- results from infection with oncogenic serotypes of HPV geon General’s report on the health consequences of that are sexually transmitted. Pap smears are still per- cigarettes and smoking. As we approach the 50th year formed, but at less frequent intervals. Testing for high- since the War on Cancer began, it is helpful to refl ect on risk HPV DNA can be conducted instead, or co-testing past and current cancer prevention and control. This can be performed [2]. There are several highly eff ec- paper focuses on 1) early detection and prevention of tive vaccines that protect against HPV infection. Active cancer and 2) cancer survivorship, areas highlighted in campaigns are underway to immunize all pre-teenage the recent Lancet Oncology Commission report on fu- girls and boys, although uptake has been lower than ture cancer research priorities in the United States [1]. expected [3]. Immunization as a cancer prevention strategy has already shown benefi t for hepatitis B virus Early Detection and Prevention of Cancer and liver cancer [4]. In the United States, HPV immuni- Cervical Cancer zation has taken on even greater importance because In the early 1970s, the only established cancer screen- of an epidemic of other HPV-associated malignancies ing test was the cervical cancer Papanicolaou (Pap) (oropharynx, anal), increasing the cancer prevention smear. During a woman’s annual pelvic examination, value of HPV immunization [5]. cervical material was spread on a glass slide, dropped There are about 10,000 new cases of cervical can- in fi xative, and sent for examination. Clinicians under- cer each year in the United States. In spite of highly stood that cancers could be detected in this way, but eff ective tests for early detection, many women are they had little knowledge of cervical cancer’s natural diagnosed with advanced local or metastatic disease history and its relationship to various risk factors (i.e., and have a fi ve-year survival rate that is just over 60 sexual behavior, human papillomavirus [HPV] infec- percent [6]. Disparities in treatment and survival out- tion, or smoking). Clinicians had only begun to routine- comes are substantial, especially for African American ly screen younger women who were sexually active. women, and much more needs to be done to improve Cervical cancer was the number one cause of female prevention and early detection of cervical cancer in all cancer deaths worldwide, prematurely taking the lives women through immunization and screening. of women in their thirties and forties. I recall taking care of young women who received a Prostate Cancer radical surgical procedure called pelvic exenteration— Other evidence-based cancer screening tests have been an attempt to eradicate advanced cervical cancer introduced over the past decades (e.g., mammography through removal of the cervix, uterus, ovaries, bladder, for breast cancer, and fecal occult blood tests, sigmoid- lymph nodes, and sometimes bowel. Radiation thera- oscopy, and colonoscopy for colorectal cancer) [7]. py was ineff ective in preventing the return of the dis- Some tests were adopted without suffi cient evidence, ease, and death by renal failure was common, due to for example, use of the prostate-specifi c antigen (PSA) Perspectives | Expert Voices in Health & Health Care COMMENTARY blood test for prostate cancer screening. The PSA test screening. However, there are signifi cant challenges was developed to detect metastatic recurrence in pros- in implementing eff ective screening programs, includ- tate cancer patients, but in the 1980s, the PSA test was ing variable access to the technology and clinical ex- rapidly adopted as a screening test without evidence pertise needed for screening [12,29]. Screening should that it reduced mortality from prostate cancer. This led also be coupled with interventions for tobacco cessa- to an explosion in the number of prostate cancers di- tion, which can greatly reduce the risk of lung cancer agnosed each year, peaking in 1992 [8,9]. Ultimately, it and other life-threatening conditions. Many individu- was recognized that the PSA test identifi ed a reservoir als who are eligible for screening are also not receiv- of indolent prostate cancers whose early detection and ing this test due to lack of insurance to pay for the treatment did not decrease mortality. Prostate cancer screening and the post-screening medical evaluations screening guidelines have since been revised, and that may be necessary. In addition, low-dose chest CT recommendations for PSA screening are much more screening often identifi es other incidental radiographic limited to populations at increased risk [8,9]. This was fi ndings, some of which are serious and others that are one of the earliest examples of an “over diagnosis of benign, leading to further invasive procedures and un- cancer”, in which screening detects nonlethal, early necessary testing. Thus, low-dose chest CT lung cancer cancers. Once an early cancer is detected, the person screening presents new ethical, social, and fi nancial is likely to receive complex therapy that can have sig- challenges, and also suff ers from “over diagnosis” [13]. nifi cant and long-term side eff ects, but the treatments do not alter the person’s lifespan. Genetic Testing for Hereditary Cancers Cancer is now preventable for a segment of the popu- Breast Cancer lation who have certain inherited cancer susceptibility Screening mammography can reduce mortality from genes [14]. There have been great advances in knowl- breast cancer among women. However, implementa- edge about familial cancer syndromes through initial tion of regular mammography screening also led to a genetic studies in families with multigenerational early rapid expansion of cases of ductal carcinoma in situ— onset cancers (e.g., breast, colon, ovary, uterus) and a noninvasive pre-cancer that was virtually nonexis- subsequent identifi cation of the associated genes. tent in the 1970s, but now accounts for about 60,000 More knowledge has also come from advances associ- new cases of breast cancer each year. As in the case ated with the Human Genome Project and laboratory of prostate cancer, many of these early breast abnor- and commercial developments leading to the wide- malities will not develop into lethal cancers. In order spread availability of clinical testing. Genetic counsel- to maximize benefi ts and reduce the harms of screen- ing and testing for cancer predisposition is now widely ing, guideline developers are currently struggling to available, providing an opportunity for carriers of del- recommend and implement more rational, risk-based eterious gene mutations to engage in more intensive approaches to breast cancer screening, matching the screening, chemoprevention, or risk-reducing surgi- woman’s risk for disease, based on age and other cal procedures. Although the opportunity to prevent factors, with the appropriate screening interval and cancers in these families is at hand, access and uptake technology. Example strategies include implement- (care delivery) barriers still exist and highlight an im- ing more frequent screening in those at high risk for portant missed opportunity [15]. breast cancer and less frequent screening in those at low risk, to minimize the likelihood of overdiagnosis Cancer Survivorship and treatment of indolent disease [10]. There are over 15 million cancer survivors today, with 18 million expected by 2022 [16] (Figure 1). When the Lung Cancer National Cancer Act was signed, there were about 3 Lung cancer is the primary cause of cancer mortality in million cancer survivors. Great strides in early detec- both men and women. Recently, the National Cancer tion and more eff ective treatments due to better un- Institute completed a very large lung cancer screen- derstanding of the biology of cancer have improved ing trial using low-dose computerized tomographic survival and patient outcomes, but these advances (CT) chest imaging in high-risk individuals [11]. The have not come without substantial personal and eco- trial was a success in terms of documenting a statis- nomic costs to patients and their families [17,18]. tically signifi cant mortality reduction associated with Fifty years ago, most cancers were treated with ex- Page 2 Published October 22, 2018 Cancer Prevention and Control: Then and Now Figure 1 | Cancer Survivors in the United States Estimated and projected number of cancer survivors in the United States from 1977 to 2022, by years since diagnosis. SOURCE: De Moor, J. S., A. B. Mariotto, C. Parry, C. M. Alfano, L. Padgett, E. E. Kent, L. Forsythe, S. Scoppa, M. Hachey, and J. H. Rowland. 2013. Cancer survivors in the United States: Prevalence across the survivorship tra- jectory and implications for care. Cancer Epidemiology, Biomarkers & Prevention 22(4):561-570. Reprinted with permission. tensive surgical resections. For example, the radical tumors often spread to distant organs (lung, bone, mastectomy for breast cancer was initiated by William liver, brain) early in the course of tumor growth. These Stewart Halsted in the late 19th century for control of occult metastatic deposits would become apparent tumors that often involved the entire breast and were months to years after removal of the primary tumor.