What is Targeted Therapy for GIST Tumours and its Cost?

Precision in Cancer Care: Understanding Targeted Therapy for GIST and Its Cost

Tyrosine Kinase Inhibitors (TKIs) are the primary targeted therapy for Gastrointestinal Stromal Tumours (GISTs). TKI costs vary widely depending on the drug. Imatinib may cost ₹440–₹2,250 per strip, while avapritinib can cost approximately ₹45,654 per month.

What are the Different Types of Tyrosine Kinase Inhibitor Drugs and Their Costs?

Tyrosine kinase inhibitor drugs are widely available in India, including a variety of targeted therapies primarily used in the treatment of GIST and other cancers. Let us discuss these drugs in detail:

1. Imatinib (Glivec) : This is the first approved tyrosine kinase inhibitor for GSIT, which doctors use both before and after surgery to shrink the tumour and prevent recurrence. Generally, a strip of 10 tablets of Imatinib 400mg can range from Rs. 440 to Rs. 2,250.
2. Sunitinib (Sutent) : A multi-target TKI, which oncologists prescribe if imatinib is ineffective during the treatment period. The cost of this drug generally ranges from Rs. 1,981 to Rs. 7,530 for a month.  
3. Regorafenib (Stivarga) : This is another TKI, recommended by doctors for third-line or later treatment options for advanced GSITs when both imatinib and sunitinib have failed. Regorafenib, used as a third-line therapy for advanced GIST, typically costs ₹9,900–₹36,965 per month depending on dosage and formulation.  
4. Avapritinib (Avyakit) : Healthcare providers mainly prescribe this drug specifically for GSITs with a PDGFRA (Platelet-derived Growth Factor Receptor Alpha) exon 18/D842V mutation. In India, a single bottle of Avyakit costs approximately Rs. 45,654 for a single month usage.

How Targeted Therapy Works?

Targeted therapy in the case of GSITs targets specific biomolecules that promote cancer cell growth and proliferation. Here, we will highlight the basic mechanism of action of target therapy for gastrointestinal cancers. These include:

• Identifying GIST Mutations : GISTs often arise due to mutations in genes like KIT (Receptor Tyrosine Kinase Receptor) or the PDGFRA gene, which produces tyrosine kinases. These mutations trigger the kinase to remain active constantly, even without any growth or proliferation signals.
• Targeting Tyrosine Kinases : Tyrosine kinase inhibitor drugs block the activity of these mutated kinases, preventing them from signalling the cancer cells to divide and grow. Additionally, these TKIs prevent metastasis in the advanced stages of GSIT.
• First-Line Treatment : Imatinib is the first-line targeted therapy for treating GIST. Sunitinib is typically used as a second-line option when resistance to imatinib occurs. These drugs have shown impressive results, turning GIST from a largely untreatable disease into a chronic condition for some patients.
• Resistance and Second-Line Therapies : While Imatinib or Sunitinib is effective in treating GSIT, some GSITs develop resistance to it due to certain genetic mutations. In these cases, doctors prescribe drugs like Regorafenib and Avapritinib for second-line treatment therapies.    

What are the Benefits of Targeted Therapy?

Here are some of the benefits of targeted therapy to treat GSIT. These are as follows:

• Precision Targeting: Targeted therapy focuses on specific molecules or pathways within the cancer cells, which minimises potential damage to healthy cells.
• Personalised Treatments: You can tailor targeted therapies based on your genetic makeup, which allows for more effective and targeted treatment plans.
• Improved Survival: Targeted therapies usually show improved survival rates and quality of life for some cancer patients.
• Early-Stage Cancer Treatment: Targeted therapy is primarily used for advanced or metastatic GIST. In early-stage cases, surgery remains the mainstay of treatment, with targeted therapy considered in select situations.
• Combination Therapy: Targeted therapy can be combined with other treatments, such as chemotherapy or radiation, to enhance their effectiveness.

Targeted therapy is a crucial component of GSIT treatment, offering a more precise approach compared to traditional chemotherapy. However, it is important to consult with an experienced oncologist to determine the most appropriate treatment plan for individual cases.