Limitations Of Current Cancer Therapies

Today, surgery, radiotherapy, and chemotherapy, i.e. 'scalpel, ray, and pill', remain the standard tumor therapies. Novel therapies like gene therapy or immunotherapy are only administered in the setting of experimental studies. In addition, outside 'school' medicine, a variety of 'alternative' treatments are sought by patients and their families who do not have full confidence in standard therapies.

This scepticism is, unfortunately, not entirely unfounded. With current therapies, between 30% and 40% of all cancer patients die of their disease (Figure 22.1). This average percentage conceals huge differences. Basal cell carcinoma and squamous carcinoma of the skin, e.g., are almost always detected before they metastasize and can be cured by local surgery, radiotherapy or drug application (^12.1). A few formerly generally lethal tumors like testicular cancers, Wilms tumors (—> 11.1) and certain hematological cancers (^10) respond excellently to current therapies. The routine establishment of stem cell transplantation has further improved the prospects of patients with hematological cancers, most impressively of children.

On the other hand, cure rates are still abysmal for some cancers that spread early and do not respond well to chemotherapy. Mortalities exceed 95% for pancreatic carcinoma, and 85% for lung cancers beyond very early stages and some acute leukemias in adults. The rates for other common cancers fall between these extremes. As a rule, carcinomas can be cured by surgery or by radiotherapy as long as they are confined to the organ where they originate (cf. 13.1, 14.1, 15.1, 18.2, 19.1). In contrast, cure rates for metastasized carcinomas have generally remained dismal, although present-day drug and radiation therapies often alleviate symptoms and prolong survival.

Regarding this state of things, two conclusions are evident.

(1) Cancer prevention is superior to cancer treatment (cf. 20.1). Therefore, prevention ought to be consigned a high priority. At the least, if cancers cannot be prevented completely, they ought be detected at an early stage, while cures are still feasible.

(2) Better therapies are required, most urgently for advanced stage and/or metastatic carcinomas.

There is a general feeling that the current therapeutic concepts are approaching their limits. With the therapeutic strategies pursued till the 1990's, quantitative improvements in the therapy of major cancers may still be achieved, but no 'breakthroughs' are expected. In a sense, therefore, the present trend towards individualization of therapy (^21.5) recognizes the limits of current therapies, while attempting to exploit their full potential.

Breakthroughs in cancer therapy are instead anticipated from novel 'molecular' approaches based on the emerging insights into the molecular biology of human cancers. It is doubtful whether such breakthroughs have already been achieved. So far, only few 'new-age' drugs developed 'rationally' on the basis of molecular biology insights have entered clinical routine (cf. 22.4). There are, however, good reasons to believe that this situation may change. After all, the molecular biology of cancer described in parts I and II of this book is largely a product of the late 1980's and 1990's and the establishment of a new cancer therapy requires at least a decade of development and testing. Moreover, in several cases in which initial attempts at molecular-based cancer therapy have not been successful, advances in the knowledge of cancer biology allow to understand why these failures have occurred and to improve on them. In fact, this knowledge has also elucidated the causes why current cancer chemotherapy is only efficacious up to a certain point.

Figure 22.1 Mortalities of selected cancers Incidence (grey) and mortality (black) of selected cancers in males in Germany in 2000. Data are from the Robert-Koch-Institute.

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