Why Does Lung Cancer Come Back? What Are The Types Of Recurrence, New Indian Study Explained

What Are The Findings?

Patients with lung adenocarcinoma carry a specific mutation in the Epidermal Growth Receptor Factor (EGFR) gene, and are treated with a class of targeted drugs called “EGFR tyrosine kinase inhibitors" that suppress the unusual growth of the cancerous cells, an Indian Express report mentioned.

But relapse happens due to patients’ resistance to these therapies.

The study analysed data from 483 lung cancer patients with EGFR mutations, and found that patients who also had mutations in certain TSGs had significantly worse survival rates.

The researchers performed detailed genetic sequencing on tumor samples from 16 patients before and after their cancer relapsed to understand how these genetic changes contribute to disease relapse. “A group of 17 TSGs that were frequently mutated in patients who relapsed early were identified. These genes were found to play a key role in driving resistance to EGFR-targeted treatments," Amit Dutt, Professor and Tata Innovation Fellow, Integrated Cancer Genomic Laboratory, Department of Genetics, University of Delhi South Campus, told The Indian Express.

An important aspect of this study was its use of liquid biopsy — a blood test that detects cancer-related DNA fragments in the blood using a comprehensive genomic profiling panel developed by One Cell Diagnostics.

It analysed 200 blood samples from 25 patients to track how the genetic makeup of the tumours evolved during the treatment. The researchers found that in patients who relapsed early (within 10 months of starting treatment), mutations in these 17 TSGs were already present.

What Are Types Of Recurrence?

After treatment, some tiny cells could be left untreated in your body that can multiply and grow in cancer again. There are three types of cancer recurrence:

Local: The cancer has come back to your lungs.

Regional: The cancer is in the lymph nodes near the lungs.

Distant: The cancer is in another part of the body, like the liver, bone, or brain. Even though it’s in a different area, it’s still called a lung cancer recurrence.

Chances of recurrence depend on the type of lung cancer and its stage. The kind of treatment that a patient has received may also play a role in recurrence.

Types Of Lung Cancer

Non-small-cell lung cancer (NSCLC) is the most common, accounting for roughly 85% of cases. The other kind is small-cell lung cancer (SCLC).

In NSCLC, the chance of a recurrence depends on the cancer stage. In general, the higher the stage, the chance of cancer spread is higher, and the greater chance that it will come back. For example, research shows that one in three people with stage I will have a recurrence. For those diagnosed with stage III, the lung cancer will return about 63% of the time.

SCLC is the most aggressive kind of lung cancer. Although SCLC responds well to treatment at first, most people will have a recurrence in a year or two. When SCLC comes back, it tends to spread faster.

Lung Cancer In India

The most commonly diagnosed cancers worldwide are lung (1.61 million, 12.7% of the total), breast (1.38 million, 10.9%), and colorectal cancers (1.23 million, 9.7%). The most common causes of cancer deaths are lung cancer (1.38 million, 18.2% of the total), stomach cancer (738,000 deaths, 9.7%) and liver cancer (696,000 deaths, 9.2%) [5].

The rate of lung cancer has surged from 6.62 per 1,00,000 in 1990 to 7.7 per 1,00,000 in 2019, and a significant rise is expected in urban areas by 2025.

According to the researchers, including experts from Tata Memorial Hospital, the ratio of lung cancer research output from India to global research output stands at 0.51. The study, published in Lancet’s eClinical Medicine Journal, showed that the lung cancer age arrives in India 10 years earlier as compared to Western countries, where the age of diagnosis is between 54 and 70.

It might be the result of India’s younger population (median age 28.2 years) compared to the USA (38 years) and China (39 years).

According to a paper in Asian Pacific Journal of Cancer Care, there is a history of active tobacco smoking in 87% of males and in 85% of females. History of passive smoking is found only in 3% cases. In India, lung cancer is most common cancer in males in all urban regions. It is estimated that every year in India about 30,000 new lung cancer cases are registered.

The ratio increases progressively up to 51-60 years and then remains the same. The smoker to non-smoker ratio is high up to 20:1 in various studies. The demographic pattern of lung cancer in India is similar to that of Western countries 40 years ago.