1 History of pediatric oncology

Pediatric oncology emerged as a distinct specialty as clinicians recognized that cancers in children differed from those seen in adults in both biology and treatment response. Early efforts focused on identifying patterns of disease, improving diagnosis, and adapting therapies that could be tolerated by younger patients. Over time, the field developed into a multidisciplinary practice combining medicine, surgery, radiation therapy, pathology, nursing, and supportive care.

1.1 Early recognition of childhood cancers

Descriptions of childhood tumors appear in older medical writings, although for many years these illnesses were poorly understood and often fatal. Childhood leukemia, brain tumors, and several solid tumors were gradually distinguished from infectious or inflammatory diseases through clinical observation and autopsy studies. Better pathology methods in the nineteenth and early twentieth centuries helped establish that children could develop distinct malignant diseases.

1.2 Development of chemotherapy and multimodal treatment

The introduction of chemotherapy transformed care by making systemic treatment possible for cancers once considered uniformly lethal. Combination regimens, surgery, and radiation therapy were then integrated into multimodal protocols tailored to specific tumor types. Cooperative clinical trials played a major role in defining effective drug schedules, refining doses, and reducing unnecessary toxicity.

1.3 Advances in survival and supportive care

Survival improved as clinicians learned to manage complications such as infection, anemia, bleeding, and treatment-related organ injury. Better imaging, laboratory testing, intensive care, antiemetic therapy, and antimicrobial support also contributed to improved outcomes. Pediatric oncology increasingly emphasized long-term follow-up, since many patients now survive into adulthood and may experience late effects of treatment.

2 Epidemiology and incidence

Childhood cancer is uncommon compared with adult malignancy, but it remains a major cause of disease-related death in children and adolescents. The pattern of cancers differs by age, with certain diagnoses clustering in infancy, early childhood, or adolescence. Incidence and survival vary across regions because of differences in detection, access to treatment, and health system capacity.

2.1 Global burden of childhood cancer

Worldwide, childhood cancer represents a relatively small fraction of all cancers but carries substantial medical and social impact. The burden includes not only mortality but also prolonged treatment, family disruption, and the need for long-term survivorship care. In many settings, outcomes are strongly influenced by whether children receive timely diagnosis and complete therapy.

Some malignancies are more common in very young children, including neuroblastoma, Wilms tumor, and retinoblastoma. Leukemias and brain tumors occur across several age groups, while Hodgkin lymphoma and bone tumors are often seen more frequently in older children and adolescents. These age patterns reflect developmental biology and differences in the tissues most vulnerable to malignant transformation.

2.3 Geographic and socioeconomic variation

Rates of diagnosis and survival vary between countries and within health systems. Differences in diagnostic resources, referral pathways, supportive care, and treatment continuity can affect reported incidence and outcomes. Socioeconomic factors may also influence the stage at diagnosis, adherence to therapy, and the ability to manage complications.

3 Classification of pediatric cancers

Pediatric cancers are commonly classified by the tissue or cell type from which they arise. This practical approach helps guide diagnosis, risk stratification, and treatment planning. Many childhood tumors are embryonal or hematologic in origin and differ from the common epithelial cancers seen in adults.

3.1 Leukemias

Leukemias are cancers of the blood-forming tissues and are among the most frequent pediatric malignancies. They usually involve abnormal proliferation of immature white blood cell precursors in bone marrow and blood. Their clinical course and treatment depend on lineage, genetic features, and disease burden.

3.1.1 Acute lymphoblastic leukemia

Acute lymphoblastic leukemia is the most common childhood cancer. It arises from lymphoid precursors and often presents with marrow failure, bone pain, fever, and fatigue. Risk-adapted therapy has produced high cure rates in many settings.

3.1.2 Acute myeloid leukemia

Acute myeloid leukemia is less common than acute lymphoblastic leukemia but is generally more complex biologically. It involves immature myeloid cells and may present with cytopenias, infection, bleeding, or organ infiltration. Treatment usually requires intensive chemotherapy and sometimes stem cell transplantation.

3.2 Brain and central nervous system tumors

Tumors of the brain and central nervous system are a major category of pediatric cancer. They may arise in the cerebellum, brainstem, cerebral hemispheres, or spinal cord, and symptoms depend on location and size. Headache, vomiting, gait disturbance, seizures, and developmental changes can be early clues.

3.3 Lymphomas

Lymphomas are malignancies of lymphoid tissue and include Hodgkin lymphoma and non-Hodgkin lymphoma. They may present with enlarged lymph nodes, fever, weight loss, chest masses, or abdominal disease. Pediatric lymphomas often grow rapidly but can respond well to modern therapy.

3.4 Solid tumors

Solid tumors in children form a diverse group with varying origins, clinical behavior, and treatment needs. They may arise from nerve tissue, kidney, bone, muscle, or other embryonal structures. Diagnosis often requires imaging, tissue sampling, and careful staging.

3.4.1 Neuroblastoma

Neuroblastoma develops from sympathetic nervous system precursor cells and often occurs in infants and young children. It may appear in the adrenal gland, chest, abdomen, or along the spine. Some tumors regress spontaneously, while others are highly aggressive.

3.4.2 Wilms tumor

Wilms tumor is a kidney cancer of childhood, usually presenting as an abdominal mass. It commonly affects young children and is often discovered incidentally by caregivers or clinicians. Treatment typically combines surgery with chemotherapy, and in some cases radiation therapy.

3.4.3 Osteosarcoma and Ewing sarcoma

Osteosarcoma and Ewing sarcoma are important malignant bone tumors of childhood and adolescence. They often cause localized pain, swelling, or a mass near the affected bone. Management usually includes chemotherapy and surgery, with radiation used in selected cases.

3.4.4 Rhabdomyosarcoma

Rhabdomyosarcoma is a malignant tumor of skeletal muscle lineage that can arise in the head and neck, genitourinary tract, or extremities. It may cause obstruction, bleeding, or a visible lump depending on its site. Therapy is usually multimodal and tailored to extent of disease.

3.5 Retinoblastoma and other rare cancers

Retinoblastoma is a malignant eye tumor of early childhood and is often first noticed because of an abnormal pupillary reflex. Other rare pediatric cancers include hepatoblastoma, germ cell tumors, and several unusual soft tissue tumors. Although individually uncommon, these entities are important because early recognition can improve outcomes.

4 Causes and risk factors

Most childhood cancers do not have a single identifiable cause. Instead, they arise from an interaction of genetic susceptibility, developmental processes, and in some cases environmental or prenatal influences. In many patients, no clear risk factor is found.

4.1 Genetic predisposition syndromes

Certain inherited syndromes increase the likelihood of pediatric malignancy. Examples include conditions associated with defects in DNA repair, tumor suppression, or developmental regulation. These syndromes may also be linked to characteristic physical findings or congenital anomalies.

4.2 Environmental and prenatal factors

Some studies have examined prenatal exposures, parental occupational factors, and other environmental influences. The evidence for many suspected associations remains limited or inconsistent. When such factors are involved, they usually explain only a small proportion of cases.

4.3 Inherited mutations and familial cancer risk

A minority of childhood cancers are associated with inherited mutations that can be passed through families. These variants may increase cancer risk by affecting cell cycle control, DNA repair, or differentiation pathways. Genetic counseling can help clarify recurrence risk and guide surveillance for relatives when appropriate.

4.4 Sporadic versus hereditary cases

Most pediatric cancers are sporadic, meaning they occur without a known inherited syndrome. Hereditary cases tend to appear in children who develop cancer at unusually young ages, have multiple tumors, or show family patterns suggestive of transmission. Distinguishing the two helps with counseling and may influence screening strategies.

5 Pathophysiology and tumor biology

Pediatric tumors reflect the biology of developing tissues and immature cell populations. Their behavior is shaped by developmental signals, genetic alterations, and interactions with the surrounding tissue environment. These features often make them biologically distinct from cancers arising later in life.

5.1 Cellular origin of pediatric malignancies

Many childhood cancers originate from precursor cells that fail to mature normally. This includes hematopoietic precursors in leukemia and embryonal cells in several solid tumors. Because these cells are already in active developmental pathways, malignant transformation can occur with relatively few changes.

5.2 Molecular and genetic alterations

Pediatric cancers often contain characteristic chromosomal translocations, amplifications, deletions, or single-gene changes. Some alterations drive rapid growth, while others affect differentiation or resistance to apoptosis. Molecular testing has become important for diagnosis, risk classification, and selection of targeted treatment.

5.3 Differences from adult cancers

Compared with adult tumors, pediatric cancers are less often linked to long-term carcinogen exposure and more often associated with developmental biology. They also tend to have fewer accumulated mutations, though specific driver alterations may be highly important. These differences help explain why treatment approaches are not simply adapted from adult oncology.

5.4 Tumor microenvironment and growth patterns

The surrounding microenvironment influences tumor growth, invasion, and response to therapy. Blood supply, immune activity, stromal support, and local tissue architecture all play roles in disease behavior. Some pediatric tumors grow quickly, while others show periods of dormancy or spontaneous regression.

6 Clinical presentation

Children with cancer may present with nonspecific symptoms that resemble common childhood illnesses. Because early signs can be subtle, diagnosis sometimes requires a high index of suspicion. Presentation varies widely according to tumor type and location.

6.1 General signs and symptoms

Common findings include fatigue, fever, weight loss, pallor, pain, bruising, and reduced appetite. Persistent symptoms that do not resolve as expected may indicate an underlying malignancy. In some cases, caregivers notice a mass, abnormal eye appearance, or changes in movement or behavior.

6.2 Site-specific presentations

Tumors in different organs produce characteristic symptoms. Brain tumors may cause vomiting or balance problems, abdominal tumors may present as distension or pain, and bone tumors often cause local pain or swelling. Eye tumors can lead to visual abnormalities, and chest masses may cause cough or breathing difficulty.

6.3 Emergency presentations

Some pediatric cancers first come to attention because they cause acute, potentially life-threatening complications. These emergencies require prompt recognition and treatment. Stabilization may be needed before definitive cancer therapy can begin.

6.3.1 Tumor lysis syndrome

Tumor lysis syndrome results from rapid breakdown of malignant cells, leading to electrolyte disturbances and kidney injury. It is most often associated with highly proliferative tumors, especially after treatment begins. Prevention and early management are essential.

6.3.2 Spinal cord compression

Spinal cord compression can occur when a tumor or associated mass presses on the spinal canal. Symptoms may include back pain, weakness, sensory changes, and difficulty walking. Rapid intervention is needed to prevent permanent neurologic damage.

6.3.3 Superior vena cava syndrome

Superior vena cava syndrome is caused by obstruction of venous return from the upper body, often from a mediastinal mass. It may produce facial swelling, prominent veins, cough, and shortness of breath. This condition can become urgent if airway compromise develops.

7 Diagnosis

Diagnosis of pediatric cancer relies on integrating clinical findings with laboratory, imaging, and pathology studies. Because many symptoms are nonspecific, evaluation is often stepwise and guided by the suspected tumor type. Accurate diagnosis is essential for selecting appropriate therapy.

7.1 Medical history and physical examination

The clinical assessment begins with a detailed history of symptoms, duration, growth patterns, prior illnesses, and family history. Physical examination looks for masses, lymph node enlargement, organomegaly, neurologic deficits, or signs of marrow failure. Findings help determine which tests are most appropriate.

7.2 Laboratory studies

Laboratory studies support diagnosis and provide a baseline for treatment planning. They can reveal anemia, cytopenias, organ dysfunction, or biochemical abnormalities linked to the malignancy or its complications. Serial testing is also used during therapy.

7.2.1 Blood counts and chemistry tests

Complete blood counts can identify leukopenia, thrombocytopenia, or abnormal circulating cells. Chemistry panels assess kidney and liver function, electrolytes, and markers of tumor lysis or organ stress. These results help guide urgent management and dosing of therapy.

7.2.2 Tumor markers

Some pediatric cancers produce measurable markers in blood or urine. These may aid diagnosis, assist in risk assessment, and provide a way to monitor response or recurrence. Marker utility varies substantially by tumor type.

7.3 Imaging studies

Imaging is used to locate disease, define extent, and assist in biopsy planning. Common methods include ultrasound, computed tomography, magnetic resonance imaging, and nuclear medicine scans. The choice depends on tumor site, age, and the need to limit radiation exposure when possible.

7.4 Biopsy and pathology

Tissue diagnosis is usually required before definitive treatment, except in selected emergencies. Pathologists examine the specimen for tumor type, grade, and histologic features, often with immunohistochemistry and molecular studies. Accurate specimen handling is critical because treatment may depend on subtle diagnostic distinctions.

7.5 Staging and risk stratification

Staging describes how far the cancer has spread, while risk stratification combines stage with biologic and clinical factors. This approach helps determine treatment intensity and expected prognosis. Risk grouping is especially important in pediatric oncology, where over-treatment can produce avoidable long-term harm.

7.6 Molecular testing and genetics

Modern evaluation often includes testing for chromosomal changes, gene fusions, mutations, and inherited susceptibility. These studies can clarify diagnosis, refine prognosis, and identify targets for therapy. Genetic counseling may be recommended when a hereditary syndrome is suspected.

8 Treatment

Treatment is individualized according to tumor type, stage, biology, and the child’s overall condition. Pediatric oncology typically uses multimodal therapy, balancing cure rates with preservation of growth and function. The treatment plan is usually coordinated by a specialized team.

8.1 Chemotherapy

Chemotherapy remains a foundation of treatment for many pediatric cancers. Drugs may be given in combinations to increase effectiveness and reduce resistance. Dosing is carefully adjusted for body size, organ function, and expected toxicity.

8.2 Surgery

Surgery may be used to remove localized tumors, obtain tissue for diagnosis, or relieve pressure from a growing mass. In some cancers it is curative; in others it is one component of broader therapy. Surgical planning aims to preserve function whenever possible.

8.3 Radiation therapy

Radiation therapy can control local disease or reduce recurrence risk in selected tumors. Because children are sensitive to radiation-related late effects, its use is carefully weighed against potential benefits. Modern techniques strive to limit exposure to healthy tissues.

8.4 Targeted therapy

Targeted therapies act on specific molecular pathways or abnormal proteins in cancer cells. Their use in pediatric oncology is expanding as biologic insights improve. These drugs may offer greater precision than conventional chemotherapy in certain settings.

8.5 Immunotherapy

Immunotherapy harnesses the immune system to recognize and attack malignant cells. Approaches include monoclonal antibodies, immune checkpoint strategies in select contexts, and cellular therapies for certain blood cancers. The field continues to evolve rapidly.

8.6 Hematopoietic stem cell transplantation

Stem cell transplantation may be used for high-risk, relapsed, or otherwise difficult-to-treat malignancies. It allows delivery of intensive therapy followed by restoration of blood-forming cells. The procedure requires specialized expertise and close supportive care.

8.7 Clinical trial participation

Clinical trials are central to progress in pediatric oncology. They test new treatment combinations, dosing strategies, supportive interventions, and biologically targeted agents. Trial participation is often encouraged when appropriate because it can improve knowledge and, in some cases, patient outcomes.

9 Supportive care

Supportive care is essential to successful cancer treatment in children. It addresses symptoms, prevents complications, and supports development, schooling, and family functioning. Many supportive measures are delivered alongside anticancer therapy.

9.1 Pain management

Pain may arise from the tumor itself, procedures, or treatment side effects. Management includes medications, procedural comfort strategies, and nonpharmacologic measures. Effective pain control improves quality of life and helps children tolerate therapy.

9.2 Infection prevention and treatment

Children receiving chemotherapy are vulnerable to infection because of immune suppression. Preventive measures may include hygiene precautions, prophylactic medications, vaccination review, and rapid assessment of fever. Prompt treatment is crucial when infection is suspected.

9.3 Nutritional support

Cancer and treatment can affect appetite, absorption, and growth. Nutritional support may involve dietary counseling, supplements, enteral feeding, or, in selected cases, parenteral nutrition. Maintaining adequate intake supports healing and treatment tolerance.

9.4 Blood product support

Anemia, thrombocytopenia, and bleeding risk are common during intensive therapy. Transfusions of red blood cells or platelets may be needed to maintain stability and enable continued treatment. Blood product use is guided by clinical status and laboratory values.

9.5 Fertility preservation

Some therapies can impair future fertility, especially certain chemotherapy agents and radiation exposures. Options may include counseling before treatment and preservation strategies when feasible. Timing is often limited, so early discussion is important.

9.6 Psychosocial and family support

A cancer diagnosis affects the child and the entire family. Psychosocial care may include counseling, school support, child life services, social work, and help with sibling adjustment. These resources can lessen distress and improve adherence to treatment.

10 Complications and adverse effects

Treatment-related complications may occur during therapy or appear years later. Clinicians monitor for both immediate toxicities and delayed consequences because childhood survivors have long life expectancy. Anticipation and early intervention can reduce morbidity.

10.1 Acute treatment toxicities

Acute toxicities often arise during chemotherapy, surgery, or radiation therapy. They may affect blood counts, the gastrointestinal tract, skin, mucosa, or specific organs. Severity depends on drug type, dose, and individual susceptibility.

10.1.1 Myelosuppression

Myelosuppression is suppression of bone marrow function, leading to low blood cell counts. It increases the risk of infection, anemia, and bleeding. Dose adjustments and supportive care are sometimes necessary.

10.1.2 Nausea and vomiting

Nausea and vomiting are common adverse effects of many cancer treatments. Modern antiemetic regimens have improved control substantially. Preventing these symptoms helps maintain hydration, nutrition, and treatment adherence.

10.1.3 Mucositis

Mucositis refers to inflammation and ulceration of the lining of the mouth and gastrointestinal tract. It can cause pain, poor intake, and infection risk. Oral care, pain relief, and nutritional support are often needed.

10.2 Organ-specific toxicity

Some therapies can damage the heart, lungs, kidneys, liver, nervous system, or hearing. The risk varies according to the specific drug or radiation field. Monitoring protocols are used to detect injury early and adjust treatment when possible.

10.3 Long-term late effects

Late effects are health problems that emerge months or years after treatment. They may involve growth, endocrine function, cognition, fertility, or organ health. Survivors often require lifelong awareness of these risks.

10.3.1 Growth and endocrine problems

Radiation and certain chemotherapy regimens can alter hormone production and growth patterns. This may lead to short stature, delayed puberty, thyroid dysfunction, or other endocrine abnormalities. Pediatric follow-up includes routine developmental assessment.

10.3.2 Neurocognitive effects

Some survivors experience difficulties with attention, memory, processing speed, or school performance. These effects are more likely when the brain has been exposed to radiation or intensive central nervous system therapy. Educational support and neuropsychological evaluation may be helpful.

10.3.3 Cardiac and pulmonary complications

Cardiac and pulmonary injury may develop after exposure to specific chemotherapies, radiation, or transplantation-related therapy. Symptoms can be subtle at first and may emerge years later. Regular surveillance helps identify decline before it becomes severe.

10.4 Secondary cancers

A small number of survivors later develop a new malignancy related to prior therapy or underlying genetic predisposition. The risk depends on the original treatment and individual susceptibility. This possibility is one reason long-term follow-up is emphasized.

11 Survivorship

Survivorship care begins once active treatment ends and continues for years or decades. It addresses recurrence surveillance, late effects, health maintenance, and developmental needs. Because many survivors enter adulthood, care must be organized across life stages.

11.1 Follow-up protocols

Follow-up schedules are tailored to the original diagnosis and treatment exposures. Visits may include history, examination, laboratory studies, and organ-specific screening. Survivorship plans often summarize prior therapy and recommended monitoring.

11.2 Monitoring for recurrence

The risk of recurrence is usually highest in the first years after treatment. Surveillance may involve imaging, laboratory tests, and symptom review according to tumor type. The goal is early detection while avoiding unnecessary procedures.

11.3 Transition to adult care

As survivors age, they may move from pediatric to adult-oriented services. This transition can be challenging because medical histories are complex and late effects may require specialized expertise. Structured handoff improves continuity and self-management.

11.4 Quality of life and rehabilitation

Quality of life encompasses physical function, emotional well-being, schooling, relationships, and participation in normal activities. Rehabilitation services may address mobility, speech, cognition, or daily living skills. Support for return to school and social life is often important.

12 Prognosis and outcomes

Outcomes in pediatric oncology vary widely by tumor type, stage, and biologic characteristics. Many childhood cancers are now highly curable, while others remain difficult to treat. Prognosis has improved overall but still depends on timely diagnosis and access to comprehensive care.

12.1 Survival rates

Survival rates are often reported as overall survival or event-free survival. These measures differ by disease and treatment era. They are useful for comparing groups but do not predict an individual child’s outcome precisely.

12.2 Risk-based outcome prediction

Risk-based models combine clinical stage, laboratory data, pathology, and molecular findings. This framework allows clinicians to intensify treatment for high-risk disease and reduce exposure for lower-risk cases. Such tailoring aims to balance cure with long-term safety.

12.3 Prognostic biomarkers

Biomarkers can indicate likely response to therapy or probability of relapse. They may include genetic lesions, protein expression patterns, or measurable disease burden. As testing improves, biomarkers have become increasingly important in decision-making.

12.4 Factors affecting long-term survival

Long-term survival is influenced by the original tumor biology, treatment response, access to supportive care, and absence of major complications. Adherence to therapy and reliable follow-up also matter. For many survivors, quality of life becomes an additional outcome alongside cure.

13 Ethical and psychosocial issues

Pediatric oncology raises ethical questions because patients are minors and treatment decisions often affect future health and development. Emotional stress, uncertainty, and family burden are common. Communication and shared decision-making are central to care.

Parents or guardians generally provide informed consent for treatment, while children who are able should provide assent when appropriate. Explanations should be age-sensitive and honest without being overwhelming. Respecting the child’s understanding supports trust and cooperation.

13.2 Communication with children and families

Clear communication helps families understand diagnosis, treatment options, side effects, and prognosis. Clinicians often adapt language to the child’s developmental level and revisit discussions over time. Good communication reduces confusion and supports decision-making.

13.3 End-of-life care

When cure is not possible, end-of-life care focuses on comfort, dignity, and family support. Symptom control, emotional preparation, and bereavement resources are key elements. Palliative care may be provided alongside treatment earlier in the illness as well.

13.4 Family dynamics and coping

A child’s illness can affect caregiving roles, finances, siblings, and parental mental health. Families may cope through practical support, counseling, spiritual resources, and connection with other affected families. Attention to caregiver strain can improve the well-being of the entire household.

14 Research and future directions

Research in pediatric oncology aims to improve cure rates while lowering toxicity and long-term harm. Advances in biology, therapeutics, and global collaboration are reshaping the field. Future progress depends on both scientific discovery and access to care.

14.1 Precision medicine

Precision medicine uses individual tumor and patient characteristics to guide therapy. This approach seeks to match treatment intensity and drug choice to the specific biology of the disease. It may reduce exposure to ineffective or excessively toxic therapies.

14.2 Genomic profiling

Genomic profiling identifies mutations, rearrangements, and other alterations that may be clinically meaningful. It can refine diagnosis and reveal therapeutic targets. As testing becomes more integrated, it supports more personalized treatment planning.

14.3 Novel drug development

New drugs continue to emerge from studies of tumor pathways, resistance mechanisms, and developmental biology. Many are designed to improve selectivity or overcome relapse. Pediatric development requires careful testing because children are not simply small adults.

14.4 Immunotherapy and cellular therapies

Immunotherapy and engineered cellular approaches have changed treatment for some blood cancers and are being explored in additional diseases. These therapies can produce strong responses but may also cause unique toxicities. Ongoing research seeks safer and more broadly effective strategies.

14.5 Global access and health equity

Improving outcomes worldwide requires more than scientific advances; it also depends on accessible diagnosis, treatment, supportive care, and follow-up. Efforts to strengthen health systems, train clinicians, and reduce disparities are central to future progress. Equity remains a major goal of the field.

</INTERNAL_LINK_CANDIDATES> Acute lymphoblastic leukemia (the most common childhood cancer) Acute myeloid leukemia (a less common pediatric leukemia with intensive treatment needs) Brain and central nervous system tumors (tumors arising in the brain or spinal cord) Lymphoma (a cancer of lymphoid tissue) Neuroblastoma (a childhood tumor of the sympathetic nervous system) Wilms tumor (a pediatric kidney cancer) Osteosarcoma (a malignant bone tumor) Ewing sarcoma (a malignant bone and soft tissue tumor) Rhabdomyosarcoma (a malignant tumor of skeletal muscle lineage) Retinoblastoma (a malignant eye tumor of early childhood) Tumor lysis syndrome (a treatment-related metabolic emergency) Spinal cord compression (pressure on the spinal canal causing neurologic deficits) Superior vena cava syndrome (obstruction of upper-body venous return from a mass) Biopsy (removal of tissue for diagnosis) Staging (assessment of cancer extent) Risk stratification (grouping patients by predicted treatment risk and outcome) Chemotherapy (drug treatment for cancer) Radiation therapy (use of ionizing radiation to treat cancer) Targeted therapy (treatment directed at specific molecular targets) Immunotherapy (treatment that stimulates or redirects the immune system) Hematopoietic stem cell transplantation (replacement of blood-forming cells after intensive therapy)