Groundbreaking Findings from IIT Madras on Inherited Breast Cancer Risks
A landmark study led by researchers at the Indian Institute of Technology Madras (IIT Madras) has uncovered that one in four Indian breast cancer patients carries inherited genetic variants associated with heightened cancer risk, with the majority falling outside the well-known BRCA1 and BRCA2 genes. This revelation challenges the current focus on BRCA-only testing and calls for a more comprehensive approach to genetic screening in India.
The research, conducted in collaboration with Karkinos Healthcare and published in BMC Cancer, analyzed germline DNA from 479 unselected breast cancer patients sourced from the National Cancer Tissue Biobank (NCTB) at IIT Madras. Using high-depth whole exome sequencing—a method that examines nearly all protein-coding genes—the team identified pathogenic or likely pathogenic (P/LP) variants in 24.6% of participants. Only 8.35% involved BRCA1 or BRCA2, leaving 16.3% in other cancer susceptibility genes.
The Rising Burden of Breast Cancer in India
Breast cancer has emerged as the most common cancer among Indian women, with an estimated 200,000 new cases annually and a projected rise of 5.6% per year. Unlike in Western populations where the average diagnosis age is around 60, Indian women are often diagnosed a decade earlier, with higher rates of aggressive subtypes like triple-negative breast cancer (TNBC), which accounts for 25-31% of cases in India compared to 10-15% globally.
This early onset and prevalence of TNBC contribute to poorer outcomes, as these tumors lack targeted therapies like hormone or HER2 treatments. Factors such as genetic diversity across India's ethnic groups, lifestyle changes, and delayed screening exacerbate the challenge, making population-specific research crucial.
Methodology: Pioneering Genomics at IIT Madras
The study leveraged the NCTB, India's first national cancer tissue biobank established at IIT Madras in 2020 with support from the Department of Biotechnology, Government of India. Samples were collected from patients at partner hospitals like Kumaran Hospital and Chennai Breast Centre, ensuring representation across ages, stages, and family histories.
High-depth whole exome sequencing (mean 200x coverage) was performed on germline DNA, followed by variant calling, annotation, and classification per ACMG/AMP guidelines. This approach surpasses traditional BRCA hotspot panels, capturing rare and novel variants unique to Indian ancestries.
- Samples: 479 patients, median age 48 years
- Sequencing: Illumina NovaSeq, exome capture
- Analysis: GATK pipeline, ClinVar/POPDYST reference
- Validation: Sanger sequencing for select variants
The data contributes to the Bharat Cancer Genome Atlas (BCGA), an open-source platform hosting multi-omics data from over 1,000 Indian cancer samples, fostering collaborative research.Explore BCGA
Key Results: Beyond BRCA – A Diverse Genetic Landscape
Of the 118 patients with P/LP variants, 67% were non-BRCA, highlighting genes like TP53 (Li-Fraumeni syndrome), PALB2, CHEK2, and ATM (DNA repair pathway). Notably, 11.9% had variants in homologous recombination repair (HRR) genes beyond BRCA, critical for PARP inhibitor therapies.
| Gene | Prevalence (%) | Associated Risk |
|---|---|---|
| BRCA1/2 | 8.35 | High-penetrance hereditary breast/ovarian cancer |
| TP53 | ~2-3 (inferred) | Li-Fraumeni, early-onset cancers |
| PALB2, CHEK2, ATM | Combined ~5 | Moderate-risk DNA repair defects |
| MLH1, NF1, RB1 | Non-BRCA positives | Other syndromes |
Additionally, 21% had actionable variants in non-cancer genes (e.g., cardiac, metabolic), and pharmacogenomic insights like DPYD variants predict 5-FU chemotherapy toxicity in ~5-10%.
Photo by Abdullah Azeez on Unsplash
Global Comparisons and India-Specific Insights
Globally, germline variants occur in 5-10% of unselected breast cancer cases, with BRCA1/2 at 2-5%. India's 24.6% rate is strikingly higher, likely due to consanguinity, founder effects, and understudied moderate-risk genes in diverse populations. TNBC patients showed higher variant rates, aligning with aggressive profiles.
This underscores the limitations of Western-centric panels; Indian guidelines must evolve to include multi-gene or exome testing.Read the full BMC Cancer paper
Clinical Implications: Shifting from BRCA-Only to Comprehensive Testing
Current BRCA panels (cost ~₹10,000-30,000) miss 67% of heritable risks. Exome sequencing (~₹30,000-50,000) offers broader coverage but needs affordability scaling. Implications include cascade testing for families, risk-reducing surgeries, enhanced screening, and tailored chemo (e.g., avoiding 5-FU in DPYD carriers).
- Precision oncology: PARP inhibitors for HRR variants
- Family screening: Identify unaffected carriers
- Chemo safety: Pharmacogenomics integration
Lead researcher S. Mahalingam emphasized: "The findings have direct implications for clinical practice and national cancer guidelines."
IIT Madras' Leadership in Cancer Genomics Research
The NCTB has banked thousands of samples, enabling BCGA's pediatric leukemia, colorectal, and pancreatic databases. Collaborations with Hyundai, Karkinos, and global partners position IIT Madras as a hub for biotech innovation. This work exemplifies how IITs drive translational research, creating opportunities for PhD/postdocs in genomics.Explore research jobs at Indian universities
Students and faculty at IIT Madras use advanced tools like NovaSeq for multi-omics, fostering startups in precision medicine. Rate professors in biotech programs to find mentors.
Challenges in Precision Oncology for India's Diverse Population
India's 1.4 billion people span thousands of ancestries, complicating variant interpretation. Western databases underrepresent South Asians, risking misclassification. BCGA addresses this with open data, but needs national expansion for equitable access.
Photo by Athul Krishna on Unsplash
Future Directions and Actionable Insights
Researchers advocate national germline screening programs, India-specific databases, and subsidized exome testing. Integrating BCGA into clinics could reduce mortality by enabling early intervention. For aspiring researchers, programs at IITs offer hands-on genomics training.Academic career advice
Patients: Discuss multi-gene testing with oncologists. Families: Consider cascade screening. Academics: Contribute to BCGA for collaborative impact.
In summary, this IIT Madras study paves the way for ancestry-informed cancer care, positioning Indian higher education at the forefront of global health research. Explore higher ed jobs, university jobs, or rate my professor to join this revolution.
