Clinical Oncology 101
Educational note: This page outlines standard clinical workflows as of 2025. It is for orientation in data and health-tech modeling, not for clinical decision-making.
TL;DR
Treating cancer requires coordinating surgery, radiation, and systemic therapies (drugs) across time. The timing of when a drug is given relative to a primary surgery (e.g., neoadjuvant vs. adjuvant) and the order in which treatments are attempted if the disease progresses (lines of therapy) are the foundational data points of any clinical oncology database.
1. Intent of Treatment
Before any intervention, oncologists define the goal:
- Curative Intent: The goal is to completely eradicate the cancer and achieve a normal lifespan. Usually applies to early-stage (I-III) solid tumors.
- Palliative Intent: The cancer is advanced (usually Stage IV) and incurable. The goal is to prolong survival, control symptoms, and maximize quality of life.
2. Timing of Systemic Therapy
When drugs (chemotherapy, targeted therapy, immunotherapy) are used alongside surgery or radiation for a curable tumor, the timing is critical.
Neoadjuvant Therapy
- Definition: Therapy given before the primary definitive treatment (usually surgery).
- Purpose:
- To shrink the tumor and make surgery easier or organ-preserving (e.g., lumpectomy instead of mastectomy in breast cancer).
- To treat microscopic disease circulating in the body early.
- To provide an in vivo test of drug efficacy. If the tumor shrinks significantly, the drug works. If it doesn't, the oncologist knows to switch strategies.
Adjuvant Therapy
- Definition: Therapy given after the primary definitive treatment (surgery) when no visible cancer remains.
- Purpose: To eliminate any undetectable microscopic cancer cells (micrometastases) that might have escaped the primary tumor and are floating in the bloodstream, thus preventing a future recurrence.
Concurrent Therapy
- Definition: Given at the same time as another treatment. Most commonly, chemotherapy given at the same time as radiation (chemoradiotherapy) because the chemo acts as a "radiosensitizer", making the radiation more effective.
3. Lines of Therapy (Metastatic/Advanced Setting)
For patients with advanced or metastatic disease, treatment is given continuously or in phases until the cancer grows (progresses) or the side effects become intolerable.
- First-Line (1L): The initial treatment given for metastatic disease. This is usually the regimen with the best evidence for extending survival.
- Second-Line (2L): If the cancer progresses on 1L (or the patient cannot tolerate it), they move to the next best standard of care.
- Third-Line (3L) and beyond: Subsequent treatments used as the cancer continues to mutate and develop resistance. In late lines, patients are often encouraged to enroll in clinical trials.
Data modeling note: The "Line of Therapy" is notoriously difficult to calculate from raw claims or EHR data because defining exactly when a line ends and another begins requires interpreting complex clinical notes about disease progression.
4. Response Assessment (RECIST)
How do doctors know if a treatment is working in a solid tumor? They measure it using scans (CT/MRI) and a standardized criteria called RECIST (Response Evaluation Criteria in Solid Tumors).
- Complete Response (CR): Disappearance of all target lesions.
- Partial Response (PR): At least a 30% decrease in the sum of diameters of target lesions.
- Progressive Disease (PD): At least a 20% increase in the sum of diameters, or the appearance of new lesions. This usually triggers a change to the next "Line of Therapy".
- Stable Disease (SD): Neither sufficient shrinkage to qualify for PR nor sufficient increase to qualify for PD.
5. Performance Status
A crucial variable in any oncology dataset is how well the patient is functioning in daily life. This determines if they can withstand aggressive treatments like chemotherapy.
- ECOG Scale: The most common scale.
0: Fully active, no restrictions.1: Restricted in physically strenuous activity but ambulatory and able to do light work.2: Ambulatory and capable of self-care, but unable to work. Up and about >50% of waking hours.3: Capable of only limited self-care. Confined to bed or chair >50% of waking hours.4: Completely disabled. Totally confined to bed or chair.
- Karnofsky Performance Status (KPS): A scale from 100 (normal) down to 0 (dead).