MRSC1010: Medical Radiation Science 1A on 13/03/2025 (Thu)

Introduction

Speaker: Leah, radiation therapy lecturerWelcome and introduction to new students. Today's focus is primarily on cancer, providing a comprehensive overview rather than delving into radiation therapy specifically.

Understanding Cancer

Perceptions of cancer often vary greatly based on individual experiences. Media portrayals tend to highlight the negative aspects, such as losing hair and enduring debilitating effects due to treatment. However, it's important to recognize that over 70% of cancer patients survive and continue to lead fulfilling lives. The experience of facing cancer can foster a sense of bravery and inspire a profound perspective on life, helping to reshape personal goals and ambitions.

Defining Cancer

Cancer is fundamentally defined as a disease characterized by uncontrolled cell growth. This uncontrolled proliferation originates from genetic changes in normal cells, which can occur in any organ or tissue within the body. One critical aspect of cancer is metastasizing, which refers to the process of cancer spreading to other body parts. In medical terminology, words like neoplasm and malignant tumor are often used interchangeably with cancer, underscoring the broad implications of cellular abnormalities.

Characteristics of Cancer Cells

Cancer cells possess distinct qualities that differentiate them from normal cells:

• They exhibit unrestricted growth and division.

• They ignore signs that typically trigger cell death, leading to their persistence in the body.

• The result of this behavior is disorganized growth, often described as messy and chaotic.

• The term tumor, derived from Latin meaning "swelling" or "enlargement," can refer to both benign and malignant forms.

Benign vs. Malignant Tumors

Benign tumors:

• Are typically well-organized and localized, meaning they do not spread to surrounding tissues.

• Generally lead to better outcomes when surgically removed due to their non-invasive nature.

Malignant tumors:

• Display disorganized and invasive growth characteristics, often leading to metastasis.

• Their growth rates can vary greatly and may pose variable risks to patients, complicating the prognosis following treatment.

Cancer Growth Rate & Margins

The growth rate refers to the speed at which a tumor increases in size. Another important concept is the margin, which denotes the healthy tissue surrounding a tumor that is removed during surgery.

• A clear margin indicates that no cancer cells are found in this surrounding tissue, providing reassurance for complete removal.

• Conversely, a negative margin signifies the presence of cancer cells, which may necessitate additional surgical procedures to ensure complete excision.

• The differentiation of cancer cells, meaning how closely they resemble the original cells from which they derived, is also vital; poor differentiation often correlates with a more aggressive tumor.

Diagnosis & Treatment of Tumors

Diagnostic Methods:

1. Imaging Techniques (such as X-ray, CT, MRI, PET scans) to visualize internal structures.

2. Laboratory Tests including blood and urine tests to identify biomarkers.

3. Biopsy: A critical step where a tissue sample is evaluated under a microscope to confirm the presence of cancer.

Treatment of Benign Tumors:

• Depending on the case, benign tumors may require various approaches including observation, surgical removal, or radiation therapy in certain instances.

Treatment of Malignant Tumors:

• Treatment strategies encompass a combination of surgery, radiation therapy, and chemotherapy.

• Targeted treatments vary significantly based on specific cancer types, emphasizing the need for personalized medicine.

Impact of Cancer on Society

According to Australian cancer statistics from 2023, there are approximately 165,000 new cases diagnosed annually. The risk of developing cancer by age 75 is estimated at 1 in 3 for women and 1 in 4 for men, making it a leading cause of death with 51,000 deaths reported in 2020. The increasing incidence is partially attributed to demographic shifts and advancements in detection and treatment methods.

Economic Burden

The economic costs associated with cancer care exceed $6 billion in Australia alone. Investment in cancer research has markedly increased from $292 million (2000-2005) to $934 million (2018-2020), highlighting the essential and often underutilized role of radiation therapy in treatment plans.

Causes of Cancer

Aetiology refers to the study of disease causes, with a focus on the genetic mutations that contribute to cancer development.Important hereditary factors include mutations in the BRCA1 and BRCA2 genes, which are notably linked to breast cancer risks.Hormonal influences may also play significant roles, with certain cancers correlating directly to hormonal levels in the body.

Environmental & Lifestyle Factors:

• These factors include exposure to pollution, certain occupational hazards, and lifestyle choices such as tobacco and alcohol use.

• Viral infections, exemplified by HPV-associated cancers, further illustrate the multifaceted nature of cancer risk.

Cancer Epidemiology

Epidemiology is the study of the incidence and distribution of a disease within populations. Key concepts include:

• Incidence: Referring to the number of new cancer diagnoses over a specified time frame.

• Prevalence: The total number of individuals currently living with cancer at any given time.

• Mortality: Calculating the number of deaths attributable to cancer within a designated period.

Differences in Cancer by Gender

In 2023, male incidence rates are approximately 90,000 cases, predominantly of prostate, melanoma, and lung cancers, whereas female incidence rates stand at 73,806 cases, primarily for breast, colorectal, and melanoma cancers. With advances in detection, the prevalence and anticipated future diagnoses are likely to increase.

Symptoms and Diagnosis of Cancer

Patients frequently detect cancer through noticeable symptoms or during routine screenings. Common symptoms associated with specific cancers may include:

• Lung cancer: Persistent cough and breathlessness.

• Breast cancer: Lumps and noticeable changes in breast appearance.

• Leukemia: Persistent fatigue and susceptibility to infections. The initial diagnosis process generally includes consultations with medical professionals, followed by necessary imaging or laboratory tests to confirm findings.

Importance of Accurate Cancer Description

An accurate description of cancer is crucial as it establishes the basis for patient prognosis and treatment options.

• Staging: A process that assesses the extent of disease spread and lymph node involvement, guiding treatment decisions.

• Grading: Evaluates the tumor's differentiation and aggressiveness, which can indicate potential outcomes.

Conclusion

The transition from symptom onset to diagnosis and subsequent treatment encompasses a complex journey for patients and their families. Understanding cancer, its multitude of treatment avenues, and the broader implications on patients and society are vital. The next lecture will focus specifically on the nuances of radiation therapy and its applications in cancer treatment.