|Year : 2018 | Volume
| Issue : 2 | Page : 23-24
Screening for early detection of cancer – Hope for cure
Tapan Kumar Sahoo
Department of Radiotherapy, HCG Panda Cancer Hospital, Cuttack, Odisha, India
|Date of Web Publication||21-Jun-2018|
Dr. Tapan Kumar Sahoo
Department of Radiotherapy, HCG Panda Cancer Hospital, Cuttack, Odisha
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Sahoo TK. Screening for early detection of cancer – Hope for cure. Oncol J India 2018;2:23-4
With improved understanding of cancer biology, through genetic and molecular researches, new advanced treatment modalities are being added to the armamentarium of cancer management. Despite these advances, mortality rate among cancer patients is still very high. This is attributed to the fact that majority of patients are diagnosed in advanced stage of the disease. Screening in both healthy and high-risk populations will give the opportunity to detect cancer at an early stage in order to improve morbidity and mortality due to cancer.
Carcinogenesis in solid tumors is a gradual process. Chronic exposure to carcinogens leads to irreversible genetic changes at cellular level, which progress over a period of time to develop into full-blown cancer. Understanding this carcinogenesis process has given an opportunity for cancer prevention at various levels such as (a) primary prevention (preventing exposure to known carcinogens so that the risk of developing cancer can be minimized. This approach is directed toward general population), (b) secondary prevention (it aims at early detection and treatment of disease. It involves screening tools and directed toward at risk population), (c) tertiary prevention (it aims for appropriate and timely treatment and rehabilitation of cancer patients so as to improve outcomes. It is directed toward diagnosed cases).
| Understanding of Cancer for Screening|| |
Cancer as an important cause of morbidity and mortality, understanding of the natural history of cancer, understanding of progression of preclinical phase to a clinical phase of cancer, and availability of safe and effective treatment are the important tools for the development of screening tests. Screening test for early-stage detection of cancer should be a proven, safe, and acceptable test.
Important issues in screening
The test's accuracy with relative lack of error is the important tool for the utility of screening. The screening may overdiagnose and detect few premalignant lesions and early invasive cancers which may not require any medical intervention in the lifetime of patients.
| Approaches for Screening of Cancer|| |
Clinical/self-examination, tumor biomarkers, Pap test and human papillomavirus testing, imaging, and circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA) are the different approaches for screening.
Skin examination for people at risk of skin cancers and breast examination by self and health-care providers have not been shown to reduce deaths from the cancer. However, such examinations may detect a lump or other unusual changes in the breast and may detect changes in skin such as new development of a mole and change to an existing mole.
Few tumor markers are used for screening of several cancers such as CA-125 for ovarian cancer, CA-15.3 for breast cancer, CA-19.9 for pancreas and gallbladder cancers, prostate-specific antigen for prostate cancer, alpha-fetoprotein for yolk-sac tumor and hepatocellular carcinoma, and carcinoembryogenic antigen for gastrointestinal, lung and ovarian cancers. However, the exact groups and the exact time schedule for these are not recommended till date.
Breast, colorectal, and lung cancers are the beneficiaries from early detection using imaging screening. Mammography plays an important role in the early detection of breast cancer particularly in the age group of 40–74 years. However, magnetic resonance imaging should be added to mammography for screening of breast cancer in women with BRCA1/BRCA2 carriers. Colonoscopy, stool-based guaiac/immunochemical testing, and sigmoidoscopy are the screening tools for colorectal cancers and generally recommended in the age group of 50–75 years. Low-dose computed tomography (LDCT) is the preferred method for screening in the early detection of lung cancer and a majority of organizations recommended annual LDCT for high-risk individuals such as patients aged 55–79 years with a >30 pack-year smoking history, former smokers who have quit within the past 15 years, or patients aged 50–79 years with more than a 20 pack-year smoking history who have additional risk factors., Transvaginal ultrasound is sometimes used in screening of women at risk of ovarian or endometrial cancer.
Pap smear and human papillomavirus testing
It detects premalignant lesions and cancers in early stage before they are symptomatic, thereby reducing the incidence of cervical cancer as well as their mortality. These tests are generally recommended in the age group of 21–65 years.
Circulating tumor cell and circulating tumor DNA
Recently, CTC and ctDNA have been introduced in the screening of cancers. A better understanding of the key biological mechanisms underlying cancer growth and dissemination may be possible due to these biomarkers. Furthermore, these markers can be used in future clinical applications in the field of surgical oncology, medical oncology, and radiation oncology.
Cancer screening, early diagnosis, prognostic assessment, evaluation and management of preoperative systemic or local therapies, postsurgical detection of minimal residual disease, and early detection of cancer relapse are the various aspects of such clinical applications. Tumor cells and tumor DNA are released into bloodstream both in the early phase of primary tumor formation and growth and from the metastatic sites. Apoptotic and necrotic tumor cells release their fragmented DNA into the circulation. Instead of primary mutation detection in tumors, CTCs and ctDNA are helpful in detecting secondary, acquired drug resistance mutations, and mechanisms. Reduced sensitivity to detect some mutations in ctDNA compared to tissue biopsies is the current limitation and should no longer remain an issue. Future clinical trials should focus on the clinical utility of CTCs and ctDNA and reliable CTC and ctDNA assays validated in international ring experiments are needed. Circulating exosomes or blood platelets may be the future candidates as novel blood-based biomarkers.,
| References|| |
Schiffman JD, Fisher PG, Gibbs P. Early detection of cancer: Past, present, and future. Am Soc Clin Oncol Educ Book 2015;35:57-65.
Kurian AW, Sigal BM, Plevritis SK. Survival analysis of cancer risk reduction strategies for BRCA1/2 mutation carriers. J Clin Oncol 2010;28:222-31.
Detterbeck FC, Mazzone PJ, Naidich DP, Bach PB. Screening for lung cancer: Diagnosis and management of lung cancer, 3rd
ed: American College of Chest Physicians evidence-based clinical practice guidelines. Chest 2013;143:e78S-92S.
Cabel L, Proudhon C, Mariani P, Tzanis D, Beinse G, Bieche I, et al.
Circulating tumor cells and circulating tumor DNA: What surgical oncologists need to know? Eur J Surg Oncol 2017;43:949-62.
Alix-Panabières C, Pantel K. Clinical applications of circulating tumor cells and circulating tumor DNA as liquid biopsy. Cancer Discov 2016;6:479-91.
Vendrell JA, Mau-Them FT, Béganton B, Godreuil S, Coopman P, Solassol J, et al.
Circulating cell free tumor DNA detection as a routine tool for Lung cancer patient management. Int J Mol Sci 2017;18. pii: E264.
Melo SA, Luecke LB, Kahlert C, Fernandez AF, Gammon ST, Kaye J, et al.
Glypican-1 identifies cancer exosomes and detects early pancreatic cancer. Nature 2015;523:177-82.
Best MG, Sol N, Kooi I, Tannous J, Westerman BA, Rustenburg F, et al.
RNA-seq of tumor-educated platelets enables blood-based pan-cancer, multiclass, and molecular pathway cancer diagnostics. Cancer Cell 2015;28:666-76.