Is Targeted Therapy Superior to Chemotherapy in Cancer Treatment?

The battle against cancer has seen numerous advancements in treatment methodologies, with targeted therapy and chemotherapy being two of the most prominent approaches. Each has its merits and limitations, and the choice of treatment often depends on the specific type of cancer.

Comparing Chemotherapy and Targeted Therapy

Some cancers, like testicular cancer, respond exceptionally well to chemotherapy, often achieving even the curing of advanced-stage disease. Other cancers benefit from the combination of chemotherapy and targeted therapy. For instance, patients with aggressive histology B cell lymphomas may receive Rituxan, which targets CD20, in combination with CHOP chemotherapy. Similarly, HER2 positive breast cancer patients often receive Herceptin, a targeted therapy directed at HER2, alongside chemotherapy.

On the other hand, certain cancers are treated almost exclusively with targeted therapies. For example, cancers driven by mutations in the EGFR gene, such as lung cancer, have shown remarkable responses to targeted drugs like Tagrisso. Kidney renal cell cancers do not typically receive chemotherapy, but rather combinations of VEGF tyrosine kinase inhibitors and checkpoint immunotherapies. Advanced melanomas, too, see success with immunotherapy or targeted treatments like BRAF inhibitors.

Antibody Drug Conjugates: A New Frontier in Targeted Therapy

One of the fastest-growing subtypes of targeted therapies involves antibody drug conjugates. These innovative treatments link an antibody to chemotherapy, allowing for targeted delivery of the chemotherapy agent to cancer cells. This method reduces side effects by enhancing the accuracy of the drug delivery and increasing the concentration of chemotherapy at the target site.

Examples include Enhertu, which is effective in HER2 positive and HER2 low cancers of various types, and Trodelvy, which aims to address a pan-cancer antigen called TROP2.

Cancer Drugs: Three Broad Categories

Cancer drugs can be broadly classified into three main categories: targeted therapy, chemotherapy, and immunotherapy. Since the focus of this discussion is on targeted therapy and chemotherapy, let's explore these further.

In certain cancers, targeted therapy has demonstrated remarkable superiority over chemotherapy. Chronic myeloid leukemia (CML) is a prime example where targeted therapy, such as inhibitors targeting the BCR-ABL protein, has led to over 89% achieving complete remission, with no significant role for chemotherapy in standard cases.

Limitations and Challenges of Targeted Therapy

Targeted therapy is highly effective in specific cases, but it is not a panacea. For targeted therapy to be effective, the identified target must be the primary cause of the cancer. In many cancers, the driving target is either unknown, or the target responsible is not the sole cause. Therefore, targeted therapy may be partially effective but often does not result in a complete cure.

Furthermore, over time, cancer cells can develop mutations that bypass the effects of the targeted therapy, leading to relapse or progressive disease. This often necessitates either the use of another targeted drug or, in some cases, a return to chemotherapy to combat the resistant cancer cells.

Chemotherapy: A Time-Tested Staple in Cancer Treatment

Chemotherapy, while often associated with severe side effects, has a long history of effectiveness. Its efficacy in various cancers has been well-documented through extensive clinical trials spanning over a century. Even in cases where targeted therapies have been developed, chemotherapy remains the go-to treatment for many cancers due to its robust track record in achieving high response rates, cure rates, and overall survival.

For instance, in acute myeloid leukemia (AML), despite the identification of specific targets, chemotherapy continues to yield the best cure rates, although with significant toxicity. Similarly, in HER2 positive breast cancer, targeted agents in combination with chemotherapy have proven to be highly effective.

However, the effectiveness of targeted therapy in combination with chemotherapy varies. Some cancers have seen improved outcomes when these methods are combined, while others have not. The combination approach may also introduce additional toxicity, further complicating the decision-making process.

In conclusion, while targeted therapy and chemotherapy each have their strengths and limitations, the choice of treatment depends on the specific type and stage of cancer. It is a multi-faceted decision that requires a nuanced approach, taking into account the potential for cure, toxicity, and overall survival. In some cases, targeted therapy may be the best option, while in others, chemotherapy or a combination of both may offer the best results.