Cancer in TB patients

Relationship between Cancer and Tuberculosis (TB)

TB and malignancy may be related in the following four ways:

1. TB as a marker for occult cancer: Occult cancer may lead to locally-reduced infection barriers and/or generalised immunosuppression, rendering a cancer patient susceptible to TB infection/ reactivation.
2. TB as a risk factor for cancer: TB may increase the risk of cancer locally and systemically through chronic inflammation, fibrosis and production of carcinogenic molecules.
3. Shared risk factors for TB and some cancers: Shared risk factors such as smoking, alcoholism, Chronic Obstructive Pulmonary Disease (COPD) and immunosuppression, including HIV, may lead to both TB and cancer, affecting both prevalent and subsequent cancer risk.
4. Treatment of cancer-fueling TB: Many cancers are treated with immunosuppressants or steroids. These drugs might induce immunosuppression in the patients undergoing treatment for cancer and hence, a flare-up of TB.

Mutual Risk of Cancer and TB

• TB patients are 2-11 times more likely than non-TB patients to develop lung cancer, according to studies.
• After cancer diagnosis, the incidence of TB also increases, both in the short term and long-term.
• All types of cancer increase the risk of the development of active TB, but with varying degrees. Haematologic cancer patients had the highest rates of active TB, followed by head and neck cancers, lung cancer and breast cancer patients.

There is intrinsic immunosuppression due to the cancer itself, immunosuppressive effects of chemotherapy, or other host factors (e.g., smoking, malnutrition) that may increase the susceptibility to both cancer and TB. Thus, there is increased incidence of TB in cancer patients, and vice-versa.

Diagnosis of TB in Cancer Patients: Under the Integrated Management Algorithm for TB disease and TB infection released by the National TB Elimination Programme (NTEP), cancer patients are first screened according to the four-symptom complex to rule out/in active TB and all presumptive TB cases need to undergo testing for TB.

Co-existence of TB and cancer poses a diagnostic challenge since clinical and radiological presentations between TB and cancers are similar, hence the need for bidirectional screening. E.g., if biopsy specimens reveal infiltration by malignant cells, still send sample for microbiological confirmation of M. tuberculosis. Thus, allowing for accurate diagnosis and initiation of anti-TB treatment instead of attributing clinical deterioration to chemotherapy complications and progression of underlying malignancy.

Diagnosis of lung cancer in TB patients is usually done in consultation with a clinical specialist and can include examination of induced sputum specimens for malignant cells, as well as use of other diagnostic tools such as Computed Tomography (CT) scans, bronchoscopy, Positron Emission Tomography (PET) scans, Magnetic Resonance Imaging (MRI), histopathology and the use of biological markers.

Treatment

TB treatment in cancer patients uses the standard DS-TB/DR-TB regimens and course, except that the treating physician should assess the drug interactions between anti-TB and anti-cancer drugs. For cancer treatment, drugs may have to be modified to accommodate anti-TB treatment and to aid better prognosis of the TB outcome. However, all decisions must be taken by a competent specialist after examining the individual case.

Curative resection, chemotherapy and radiation therapy are the mainstay treatment options for cancer in TB patients. Co-existence of TB in cancer patients necessitates anti-TB treatment with extended duration, if required. Follow-up during and after treatment also follows prevailing guidelines.

Prevention

Under the NTEP, TB prevention in cancer patients is essential and includes:

• Regular screening for signs and symptoms of TB infection among all patients on immunosuppressive therapy and anti-Tumour Necrosis Factor (TNF) medicines.
• Education and referral of patients who do not have TB symptoms for TB infection testing/assessment of their eligibility for TPT.

Resources

• NTEP at a Glance; Comprehensive Clinical Management Protocol of Tuberculosis, 2022.
• Training Modules (1-4) for Programme Managers and Medical Officers, 2020.
• Tuberculosis and Risk of Cancer: A Danish Nationwide Cohort Study, D. F. Simonsen et al., International Journal of Tuberculosis and Lung Diseases, The Union, 2014.
• Increased Risk of Active Tuberculosis after Cancer Diagnosis, Dennis F. Simonsen et al., Journal of Infection, 2017.
• Pulmonary Tuberculosis as Differential Diagnosis of Lung Cancer; MLB Bhatt et al., South Asian Journal of Cancer, 2012.

Assessment