Personalized Cancer Therapy in Gurgaon

What is Next-Generation Sequencing?

A host of cutting-edge personalised cancer therapy and treatment options are now available for cancer patients in Gurgaon. Next-Generation Sequencing (NGS) is also referred to as “deep sequencing” or “massive parallel sequencing”. NGS is a broad term that encompasses a number of broad sequencing technique, such as whole genome sequencing (for sequencing the whole human genome), whole exome sequencing (for sequencing the exome, the protein-coding regions of the human genome that constitute about 1% of the human genome), RNA sequencing (for transcriptome analysis), and bisulfite sequencing (for epigenomic profiling). All the genetic and epigenetic alterations in the cancer cells can be identified by NGS techniques rather than the identification of a few targeted alterations by targeted panels. This technique enables the identification of various individual-specific genetic/epigenetic alterations besides the common genetic alteration observed in a particular cancer type, and thus, have a potential role to play in the development of personalized medicine, a futuristic perspective of Personalised cancer doctor in Gurgaon.

How NGS Works?

NGS utilized different solid supports (commonly known as chips or flow cells) to immobilize millions of DNA fragments to be sequenced in parallel. Each DNA strand is uniquely placed on the array of solid support and sequenced in parallel. Thus, this technique enables the parallel sequencing of millions of DNA fragments representatives of the whole genome. 

The number of times an individual base is sequenced is known as depth of coverage (DOC). High DOC is generally required for the sequencing cancer genome due to high heterogeneity in cancer cells. Although an increase in the DOC increases the reliability of the sequencing or the chances of all mutation getting identified, it also increases the cost of analysis and the amount of data generated per analysis.

Two types of methods are most widely used for NGS of the DNA, Ion Torrent and MiSeq. In Ion Torrent method, the sequencing is achieved by measuring the change in pH due to the release of a hydrogen ion during DNA polymerase reaction using an integrated semiconductor array for non-optical sequencing. In MiSeq method, a “sequencing by synthesis” approach is utilized wherein sequencing is done by serial additions of ?uorescent-labeled nucleotides to immobilized products across a two-dimensional array that allows for parallel sequencing of thousands of nucleotide strands. Different studies have demonstrated a high degree of concordance between the two systems. Also, some studies have advocated the use of both systems simultaneously with one confirming the mutations found by another technique.

What are the advantages of NGS?

Cancer is believed to be a genetic disease i.e. various genetic mutations build-up to give rise to cancer. These mutations may be inherited in some cases or in most cases developed due to exposure to different environmental risk factors. This is why most cancers affect old age individuals in Gurgaon. personalised cancer treatment doctors in gurgaon

Although similar cancer types share some common characteristics and prognosis, each individual is unique and have a unique set of genetic mutation leading to the disease. NGS has high sensitivity for the identification of all of the concomitant genetic mutations along with the most common mutations previously reported for the disease. This enables the physician to select the most appropriate existing therapy for the patient. 

A few cancer types are particularly susceptible to targeted therapy. In such cases, the role of NGS is indispensable for the selection of most appropriate targeted therapy among the various available options with minimal side effects for the patient. Also, in a few cases when the disease is not responding to the available standard therapy, the role of NGS become crucial to identify the driver mutations, and thus, the appropriate targeted therapy.

With the advancement in technology, various new aspects of NGS are evolving that have a potential role in the development of precision medicines. Various applications of the newly available NGS methods include gene fusion detection by sequencing RNA/cDNA, micro microsatellite instability detection by sequencing repeated regions or by evaluating the mutational signatures, detection of cancer (or recurrence in case of treated patients) by sequencing circulating tumor DNA, and others. 

What are the Limitations of NGS?

it is imperative to note that whole-genome sequencing of many cancers has revealed several thousands of mutations, out of that only a few mutations are responsible for the development of cancer (known as driver mutations) while most of them do not have any role in the development of cancer (known as passenger mutations). Also, due to the heterogenicity of cancer, all cancer cells do not contain the same mutations, which means the mutations detected in the sample might not represent the mutation in all existing cancer cells. Moreover, mutations in cancer cells might evolve over time, that is, mutations detected at one particular time might not represent the mutation present after some time. All these factors limit the use of NGS for designing a robust targeted medicine that can be beneficial for all patients with a particular cancer type. 

Many targeted drugs beneficial at a particular time generally become useless after some time due to the evolution of cancer cells with different mutations. Last but not least, NGS may detect sporadic mutations for which there is no targeted therapy available. Thus, patients would have the only choice to continue the available standard therapy. In such cases, participating in a clinical trial testing an investigational drug may prove to be beneficial.