Abstract PL02-04: Cancer screening in developing countries
Authors: Sankaranarayanan Rengaswamy 
Published: May 2012

PL02-04

Cancers of the uterine cervix, breast and oral cavity are major cancers in developing countries which are amenable for control by screening. In recent years, an increasing burden of colorectal cancer is being observed in many medium-resourced countries. Currently, most cancer patients present in advanced stages in developing countries due to lack of effective screening programs.

Cervical cancer prevention efforts world-wide have so far relied on cytology screening which requires complex resources and inputs. In most routine settings, cytology has been shown to be poorly to moderately sensitive (20-70%). Existing cytology screening programs in some low- and medium-resource countries such as Argentina, Brazil, Cuba and Mexico among others had no or limited success in reducing cervical cancer burden. Of late, cervical cancer screening programs in countries such as Brazil, Chile, Costa Rica, Mexico, Singapore, Thailand and South Korea are being re-organized. The difficulties in implementing cytology screening have prompted the evaluation of alternative tests such as HPV testing and visual inspection with acetic acid (VIA) and visual inspection with Lugol’s iodine (VILI).

A number of studies have addressed the accuracy of Pap smear and the alternative tests in detecting CIN and the feasibility, effectiveness, cost-effectiveness, safety and acceptability of innovative programmatic approaches such as a single round of screening aiming at high coverage of targeted women, restricting the target population to women aged 30-59 years and a single-visit approach combining testing and treatment (‘screen and treat’) or testing diagnosis and treatment in one session to improve overall participation. HPV testing has clearly a higher sensitivity (pooled sensitivity 90%), but somewhat lower specificity (pooled specificity 88%) than cytology. However, it is limited by its high cost, cumbersome procedure and equipment, and there are efforts to develop inexpensive, rapid, yet accurate HPV test formats. Visual screening tests based on acetic acid (VIA) or Lugol’s iodine (VILI) application have somewhat moderate sensitivity (45-85%) and low specificity (40-86%), but real time results allow immediate treatment. The current evidence supports the use of VIA and/or VILI in countries where good quality cytology or HPV testing are not feasible and not available. The safety, acceptability, and the feasibility of combining VIA or HPV screening and cryotherapy in a single-visit approach have been demonstrated in rural Thailand, Ghana, Guatemala and South Africa. There are efforts currently focusing on developing simple, affordable, safe, accurate, reliable, rapid, portable and acceptable biochemical tests for use in low-resource settings. One is a rapid-batch test (careHPV test) that detects oncogenic HPV DNA, which is expected to be commercially available in 2009.

In a randomized trial in South Africa, cryotherapy for HPV test-positive women resulted in 77% and 74% decline in the prevalence of CIN 2-3 at 6 and 12 months respectively, while VIA followed by cryotherapy resulted in a 37% and 46% lower prevalence compared with a control group. A 25% reduction in cervical cancer incidence and a 35% reduction in mortality following a single round of VIA screening have been shown in a randomized trial in India. The results on the comparative effectiveness of a single round of screening with Pap smear, HPV testing or VIA from a randomized trial in India are expected in late 2008.

Oral cancer is often preceded by precancerous lesions such as leukoplakia, erythroplakia, lichen planus and submucous fibrosis. Early oral cancers clinically present as small indurated ulcers, surface thickenings, nodules, reddish velvety areas or ulceroproliferative growths, often with no symptoms. Both oral precancerous and early suspicious cancerous lesions can be readily clinically detected by trained clinicians, nurses and auxiliary health workers, by a systematic visual oral inspection and by palpation of oral mucosa and neck. Oral visual inspection has been shown to be a sensitive and specific test to detect oral precancerous lesions and early asymptomatic oral cancers in several studies; the sensitivity of visual examination for detecting oral lesions varied from 58 to 94% and the specificity from 76 to 98%. In a community-based cluster-randomized controlled oral cancer screening intervention trial involving three rounds of oral visual inspection at 3-year intervals provided by trained health workers during 1995-2004 in Trivandrum, South India, a statistically significant 33% reduction in mortality was observed among tobacco and/or alcohol users as compared to similar control subjects. Based on the findings from this study, routine use of oral visual screening among tobacco and/or alcohol users is an effective method of reducing oral cancer in addition to primary prevention efforts to reduce tobacco and alcohol use. The very low risk of oral neoplasia among non-users of tobacco or alcohol or both justifies the restricted use of screening among high-risk individuals. Considering the fact that oral cavity assessment is an integral part of a general physical examination, awareness among health care providers on the effectiveness of oral visual inspection is critical in the early detection of oral neoplasia.

Breast cancer incidence is increasing in all developing countries and effective control measures are urgently required to reduce mortality. There are no safe and effective primary preventive measures available now to reduce the burden of breast cancer. Currently, more than two-thirds of breast cancer cases are detected in advanced stages in low-resourced countries. Methods for early detection of breast cancer include screening by mammography, clinical breast examination (CBE) and breast self-examination (BSE). It is not feasible to implement mammography-based screening in developing countries for several decades to come. There is uncertainty about the magnitude of benefit of organized CBE screening due to inconsistent findings. Results from a large on-going randomized controlled trial of CBE screening on breast cancer mortality in Mumbai involving around 300,000 women are eagerly anticipated. A significant early detection associated with CBE is evident in this study. It seems that much could be achieved towards early detection by a package of interventions consisting of increased breast awareness, physical examination of the breast and improved access to diagnosis and treatment and evaluation of this approach is a major research priority. Currently, a randomized controlled trial involving 150,000 women is evaluating this approach in reducing breast cancer mortality in Trivandrum district, India.

Another research priority is to evaluate the impact of improving awareness and health services on clinical down-staging of cancers in routine health care settings, since clinical down-staging offers an intermediate solution for countries where organised screening programs are not feasible, due to inadequate human resources and inadequately developed health service infrastructure.

The large body of research findings and managerial guidelines, as well as further information from on-going studies on the cost-effectiveness of different screening approaches should be taken into account while organizing screening programs in low- and medium-resource settings. It is important to emphasize that the critical needs for a successful screening program include educational activities, adequate human resources for screening, diagnosis and treatment, information systems to evaluate inputs and outcome and sufficient financial resources in a nation-wide context. Improved awareness among the public and health care providers, supported by developed and accessible health services are critical for screening programs. Thus direct investments are required in many developing countries for implementing screening programs.

Citation Information: Cancer Prev Res 2008;1(7 Suppl):PL02-04.