1.13 Cancer Epidemiology, Screening & Diagnostic Evaluation

Why Evaluation Content Appears on the ARRT Exam

Under Patient Care → Patient and Medical Record Management → Evaluation, ARRT expects entry-level therapists to understand epidemiology and etiology concepts, cancer screening, signs and symptoms, history and physical findings, and how imaging, laboratory, surgical, and pathology data feed the treatment record. This is not a public-health elective. It is the clinical context for reading a chart before simulation and treatment delivery.

Therapists rarely assign formal stage or order screening tests, but they must recognize why a patient arrived with a given diagnosis, which comorbidities travel with high-risk exposures, and which documents confirm site, laterality, and intent before immobilization.

Epidemiology and Etiology Basics

• Incidence: new cases in a defined population over a defined time period
• Prevalence: existing cases at a point in time or during a period
• Risk factors: exposures or traits that raise the probability of developing cancer

Therapists do not diagnose etiology, but recognizing risk-factor patterns supports patient education and explains why certain toxicities and comorbidities cluster. Heavy smokers often present with COPD and limited breath-hold capacity. Patients with alcohol-associated head-and-neck disease frequently need early nutrition and airway awareness. Hepatobiliary cases may carry cirrhosis-related lab abnormalities that affect contrast CT simulation decisions.

Prevalence vs incidence in clinic language

High incidence cancers (breast, prostate, lung, colorectal) dominate daily linac schedules. A disease can have moderate incidence yet high prevalence when survival is long, which is why survivors and re-irradiation consults appear in chart queues. Exam items may ask you to distinguish new-case rates from existing-case burden without requiring memorization of national registry percentages.

Cancer Screening vs Diagnostic Workup

Screening tests asymptomatic people at elevated risk to find disease earlier. Diagnostic tests evaluate signs, symptoms, or abnormal screening results.

After a positive screen or symptomatic presentation, staging workup may include CT, MRI, PET/CT, endoscopy, biopsy, and labs (CBC, metabolic panel, tumor markers such as PSA). The radiation therapist reviews these reports to confirm site, laterality, and clinical context before immobilization and beam delivery.

Screening pitfalls therapists should recognize

• An incidental PET-avid finding is not the same as a completed staging package.
• Screening modality does not equal treatment modality: low-dose CT screening is diagnostic imaging, not therapeutic radiation.
• Negative screening history does not rule out cancer; many radiation patients present with symptoms after never participating in organized screening.
• Shared decision-making language around PSA means the chart may show declining screening rather than a missed diagnosis.

Signs, Symptoms, and History Clues

Chart review should flag:

• Chief complaint and duration (hemoptysis, dysphagia, rectal bleeding, bone pain, neurologic deficit)
• Prior surgery, chemotherapy, immunotherapy, or hormone therapy
• Prior radiation (re-irradiation and cumulative dose concerns)
• Performance status and comorbidities affecting setup tolerance
• Allergies, anticoagulation, implantable devices, and infection-control status

Pathology and staging linkage

Pathology reports establish histopathologic type (carcinoma versus sarcoma versus hematologic disease) and grade. Staging systems such as TNM and Ann Arbor (lymphoma) organize anatomic extent. Therapists do not assign formal stage, but must recognize that prescription intent (definitive, adjuvant, or palliative) and field design follow stage and histology documented in the record.

When pathology and imaging disagree on extent, stop and escalate rather than inventing a compromise target. The evaluation package exists so simulation and delivery mirror the oncologist’s documented disease description.

Imaging Studies and Other Diagnostics in the Evaluation Bundle

Connecting evaluation data to daily therapist decisions

• Oxygen dependence and dyspnea from lung disease change immobilization and timing of imaging.
• Pain from bone metastases may require premedication before lengthy simulation.
• Prior neck dissection or reconstructive flaps change surface landmarks and mask fit.
• Rising PSA after prostatectomy changes salvage-versus-palliative framing even when the therapist does not interpret the lab alone.

Clinical Scenarios

Scenario A — screen-detected lung cancer. A 55-year-old with a 40-pack-year history has an LDCT-detected nodule, PET-avid mediastinal nodes, and biopsy-proven adenocarcinoma. Before CT simulation, expect thoracic immobilization needs, possible respiratory motion management discussion, and review of nodal stations referenced in notes. Do not treat the case as an incidental soft-tissue mass without epidemiologic context.

Scenario B — symptomatic colorectal presentation. A patient with rectal bleeding skipped colonoscopy screening for a decade. Staging MRI and endoscopy describe a low rectal primary. Simulation planning must account for full-bladder or empty-rectum instructions documented in the education plan, and the therapist should anticipate skin and bowel side-effect teaching tied to pelvic fields.

Scenario C — inherited-risk breast case. A young patient with a BRCA-associated diagnosis may have bilateral surgical history or reconstruction hardware. Evaluation notes about laterality, expanders, and prior radiation are mandatory verification items before any tangent or regional-nodal setup.

Connecting Evaluation Data to the Treatment Record

ARRT expects therapists to recognize what belongs in evaluation documentation:

• Epidemiology and etiology clues in the history of present illness
• Screening pathway that discovered disease (program-based versus incidental versus symptomatic)
• Signs and symptoms prompting diagnostic imaging
• History and physical findings affecting setup (pain, oxygen dependence, limited abduction, neurologic deficits)
• Imaging studies (CT/MRI/PET) and other diagnostics (labs, operative notes, pathology)

Worked chart-review pattern

1. Identify primary site and histology from pathology.
2. Note stage language (TNM or Ann Arbor) and intent (definitive, adjuvant, palliative).
3. List prior therapies that change tolerance (chemotherapy, surgery, prior radiation).
4. Flag labs that gate procedures (CBC before marrow-toxic concurrent chemoradiation; creatinine/eGFR before contrast CT simulation).
5. Confirm laterality and site match consent, prescription, and setup notes.
6. Capture screening-versus-diagnostic pathway in plain language so education stays accurate.

Incidence Patterns Therapists Actually See

High-volume clinics commonly treat breast, prostate, lung, and colorectal cancers because population incidence is high. Less common diagnoses (sarcomas, some pediatric tumors, rare head-and-neck subsites) still appear and require careful site-specific immobilization knowledge. Understanding incidence does not replace site anatomy study, but it explains why certain side-effect pathways and emergency presentations such as superior vena cava syndrome or cord compression recur in teaching cases.

Keep evaluation literacy practical: the exam rewards connecting risk history, screening pathway, and diagnostic documents to safe simulation and delivery decisions, not memorizing registry tables.