Lung cancer screening: The Thailand perspective

Shobha Shukla and Bobby Ramakant, CNS (Citizen News Service)
Dr Natthaya Triphuridet
The survival rate for lung cancer is strongly related to the stage of the disease. The earlier its detection, the better its survival rate. “Currently, low-dose computed tomography (LDCT) is the standard technique for lung cancer screening. The National Lung Screening Trial (NLST), launched in 2002, found that screening with LDCT resulted in a 15-20 percent lower lung cancer-specific mortality and 6.7 percent lower all-cause mortality relative to chest radiography (X-ray) over a median of 6.5 years of follow-up,” said Dr Natthaya Triphuridet, Pulmonologist and Assistant Director for Medical Affairs at Chulabhorn Hospital, Bangkok, Thailand.

Dr Triphuridet is among the faculty members of the International Association for the Study of Lung Cancer (IASLC) Asia Pacific Lung Cancer Conference (APLCC 2016).

Dr Triphuridet added, “Since the release of the NLST data, many guidelines have endorsed the use of LDCT screening for high-risk individuals. In 2013, the U.S. Preventive Services Task Force (USPSTF) recommended annual screening for lung cancer with LDCT in adults aged 55-80 years who have a 30 pack-year tobacco smoking history and currently smoke or have quit within the past 15 years. The numbers needed to screen (NNS) to prevent 1 lung cancer death was 320 among participants who completed 1 screening, and was 219 to prevent 1 death overall over 6.5 years. These benefits are comparable to NNS with mammography of 1339 to prevent 1 breast cancer death after 11-20 years of follow-up, and NNS with flexible sigmoidoscopy of 817 to prevent 1 colon cancer death.”

Major advancements in early diagnosis, but challenges remain

Despite the pivotal results of LDCT, there are many concerns regarding high false positives (96 percent), over diagnosis, accumulation of radiation exposure, and high cost of screening.

Tuberculosis (TB) and lung cancer: Sinister linkages?

According to Dr Triphuridet, generalization of lung cancer screening with LDCT in the TB endemic Southeast Asia region, a geographic area that accounts for 41 percent of the global TB burden, is very challenging.

“TB mimics lung cancer. Pulmonary TB may present as an asymptomatic solitary pulmonary nodule, imitating early stage lung cancer. Symptoms of cough, hemoptysis, chest pains, weakness, weight loss, fever, and night sweats are common in both active pulmonary TB and symptomatic lung cancer. The radiographic findings of TB can mimic lung cancer, such as mass-like lesion, solitary/multiple pulmonary nodule(s), mediastinal lymph node enlargement, or pleural effusion. These findings are also important in staging of non-small cell lung cancer in the TNM system: Size of primary tumour (T), Mediastinal lymph nodes (N), and metastasized (M) to other organs of the body,” she said.

“Furthermore, pre-existing TB increases risk of lung cancer and lung cancer may promote TB infection or reactivation of latent TB infection, or cause new exogenous infections. All this makes it difficult to manage screening, diagnosis, staging, treatment, monitoring, and surveillance of lung cancer in TB-endemic areas. No clear evidence of lung cancer screening benefit has been established in high-risk populations in a TB endemic area.”

Thailand’s lung cancer screening project

Dr Triphuridet, who is also the Principal Investigator of the Integrative Lung Cancer Screening Project in Thailand, shared the findings of a five-year “Integrative Lung Cancer Screening” project using LDCT that was started at Chulabhorn Hospital in Thailand in 2012. The study’s objectives were to:
  • Determine the role of lung cancer screening using LDCT in a high-risk population residing in Thailand—a high TB-burden country; and to
  • Study an alternative screening modality called chest digital tomosynthesis (DT) that is reported to be as sensitive as CT for the detection of actionable lung nodules with a much lower radiation dose and lower cost compared with LDCT.

Former and current heavy smokers (>30 pack-years) aged 50-70 years, without a history of active TB within a recent year, were included in the study. Out of the 634 high risk subjects (mostly males) investigated, 66 percent had lung nodule(s) in their initial LDCT screening (58 percent with multiple nodules). Nine out of these 634 cases (1.4 percent) were diagnosed to have lung cancer - five of stage I, one of stage II/III, and two of stage IV lung cancer. All six cases of stage I and II had multiple lung nodules, while three cases of stage III and IV had a single lung nodule.

Dr Triphuridet received the IASLC Global Mentorship Award in 2013 for “Screening of Lung Cancer by Low-Dose CT (LDCT), Digital Tomosynthesis (DT) and Chest Radiography (CR) in a High Risk Population.” Dr. Triphuridet shared that the study showed that, despite a high burden of TB in Thailand, LDCT screening in heavy smokers could yield a high rate of primary lung cancer in high risk populations. However, high prevalence of lung nodules is one of the major problems in diagnosis and staging of lung cancer in endemic areas of TB.

Integration of smoking cessation in lung cancer screening 

“All study participants were also made to realize the harmful effects of tobacco smoking and smoking cessation clinics were integrated with the lung cancer screening programme,” shared Dr Triphuridet. “As per the WHO Report on the Global Tobacco Epidemic 2015, at present 19.9 percent of adults in Thailand are tobacco smokers (39 percent males and 2.1 percent females). There is data that shows a strong linkage between smoking cessation rate and cost-effectiveness of CT screening. For example, at the smoking cessation rate of 3 percent, the annual screening for smokers aged 50-74 years (with 40-pack years) costs $110,000-$166,000/QALY (quality-adjusted life-years gained). But, if the cessation rate is doubled the cost is reduced to <$75,000/QALY. If quit rates are halved, benefits from screening are almost wiped out.” Thus, integration of smoking cessation practices into lung cancer screening programmes is an important step in improving the cost-effectiveness of screening.

Challenges in implementing LDCT in Thailand 

Currently, only a few hospitals, including Chulabhorn Hospital, offer lung cancer screening to heavy smokers. While admitting that there are many challenges in the implementation of LDCT screening in Thailand, Dr Triphuridet advocates, “For maximizing the benefits and minimizing the risks of screening, and promoting efficient utilization of healthcare resources, screening referral centre models may be useful for initial implementation of lung cancer screening with LDCT. The screening referral centre comprises a multidisciplinary specialized team of radiologists, pulmonologists, thoracic surgeons, and medical/radiation oncologists, who are capable of developing standardized practices (including lung nodule management protocol and interventions, diagnosis, staging, and treatment) and integrating smoking cessation practice into screening programmes to improve the cost-effectiveness of lung cancer screening and studying the remaining areas of uncertainty regarding lung cancer screening.”

Shobha Shukla and Bobby Ramakant, CNS (Citizen News Service)
13 May 2016