Cancer is increasingly seen as an interplay of inherited susceptibility and environmental exposure. Discuss with reference to India's cancer-screening strategy.

In 1925, Dr. Louis Sambon's epidemiological study found that "cancer houses" and "cancer areas" exist. This was an early sign that cancer clusters can come from shared surroundings and not only from shared genes [1]. Today, WHO notes that only about 10% of children with cancer have a genetic predisposition [2]. Most cancer arises when inherited risk meets exposure, so India's screening strategy must address both.

Interplay of inheritance and environment

• Inherited (germline) susceptibility: variants in genes such as BRCA1/2 raise the risk of breast and ovarian cancer. Close relatives of a carrier may share that risk.
• Environmental exposure: chronic infections (HPV, hepatitis B/C, H. pylori) cause a substantial share of cancers [3]. Tobacco, diet and pollution add more.
• Interaction: familial clustering is not the same as heredity. A family shares genes, but it also shares food, water and smoke [1]. A gene raises risk, and exposure often decides whether cancer actually appears.

India's screening strategy: strengths

• Under NP-NCD, everyone aged 30 and above is screened for oral, breast and cervical cancers at Ayushman Arogya Mandirs [4]. These are largely exposure-driven cancers.
• GenomeIndia (DBT) has sequenced 10,074 genomes from 83 populations [5]. This gives India its own reference data for reading genetic test results.

Gaps

• Screening is age-based, not risk-based. There is no family-history step, so high-risk hereditary families go unflagged.
• Genetic testing is limited to tertiary centres. Many results come back as "variants of uncertain significance" because reference panels are mostly Western.
• Genetic data raises questions of privacy, consent and discrimination, which fall under the DPDP Act, 2023.

Way forward

• Add family-history questions to the NP-NCD screening visit [4]. Follow this with cascade testing of carriers' relatives.
• Build Indian variant panels from GenomeIndia data to reduce uncertain results [5].
• Keep prevention as the main tool: HPV vaccination, hepatitis control and tobacco cessation [3].

Cancer comes from genes and environment working together. India's screening model handles the environmental side well but largely misses the inherited side. A risk-stratified approach would fix this: population screening for everyone, targeted genetic testing for high-risk families, and prevention at the centre. This would advance SDG 3.4 (cutting premature NCD deaths) and the Article 21 right to health.