Oncology Principles
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Direct answer
Stage answers how far, grade answers how fast — open every cancer discussion with those two measurements and the rest of oncology becomes a decision tree. Staging uses the TNM system (tumour extent, nodal status, distant metastasis, grouped into stages I-IV) measured clinically, endoscopically, radiologically and pathologically; grading reads the histological aggressiveness from well through moderately to poorly differentiated. Around them sit the principles: carcinogenesis proceeds through initiation (irreversible DNA change by a carcinogen), promotion (reversible proliferation driven by promoters such as hormones or irritants) and progression (acquired autonomy and spread); causes in Indian practice cluster around tobacco, alcohol, infections (HPV, hepatitis B and C, Epstein-Barr virus) and radiation. Treatment intent is curative or palliative, modality single or combined — surgery, radiotherapy and chemotherapy arranged as neoadjuvant (before, to shrink), adjuvant (after, to clear residual disease) or concurrent — and the plan is made by a multidisciplinary team against the patient's performance status, not by any single specialist's preference.
What you must remember
- Carcinogenesis cascade: initiation by a carcinogen (irreversible mutation), promotion by reversible stimuli, progression to invasion and metastasis — the framework that explains why tobacco cessation works even decades into habit, and why premalignant lesions are watched.
- Oncogene versus tumour suppressor logic: oncogenes are gain-of-function dominants (RAS, MYC), tumour suppressors are recessive loss-of-function (p53 — the most commonly mutated gene in human cancer, RB in retinoblastoma); viral examples include HPV E6 and E7 proteins disabling p53 and RB in cervical and oropharyngeal cancer.
- TNM staging with a dental example: oral cavity — T1 up to 2 cm, T2 up to 4 cm, T3 larger, T4 invading adjacent structures (with depth-of-invasion refinement in current AJCC editions); N by node number, size and laterality; M by distant spread; stage grouping drives treatment and prognosis more powerfully than grade.
- Grading: well, moderately and poorly differentiated from nuclear atypia, mitoses and architecture; graded but not staged examples include lymphomas (Ann Arbor) — a favourite distinction question.
- Performance status scales: Karnofsky 100 to 0 and WHO/ECOG 0 to 5 — ECOG 3-4 patients generally cannot tolerate cytotoxic chemotherapy, the practical threshold every oncology viva expects.
- Modality grammar: surgery for local disease, radiotherapy for locoregional, chemotherapy and targeted agents for systemic; neoadjuvant downsizes (for example locally advanced breast or oral cancers), adjuvant sterilises residual microscopic disease, concurrent chemoradiation radiosensitises in head and neck cancer, palliative therapy relieves symptoms without curative intent.
- Tumour markers with honest caveats: PSA (prostate), CEA (colorectal — monitoring more than screening), CA-125 (ovarian), AFP (liver, yolk sac), beta-hCG (trophoblastic, testicular), calcitonin (medullary thyroid) — useful for monitoring and staging adjuncts, not standalone diagnosis.
- Follow-up discipline: most recurrences of head and neck cancer declare within two years — structured surveillance in that window, with tobacco and alcohol cessation as part of the prescription.
From biopsy to plan: the pathway of a new cancer patient
A confirmed squamous carcinoma of the tongue in a 55-year-old chewer walks a fixed road, and the order of the milestones is examinable. First, completeness of diagnosis: site, size, depth of invasion, histological grade, perineural or lymphovascular invasion from the histopathology form. Second, staging: contrast CT or MRI of the primary and neck, chest imaging, and PET-CT where indicated — written as cTNM before surgery and pTNM from the specimen. Third, host assessment: performance status, nutrition (weight loss over 10 per cent is a red flag needing dietetic support), comorbidity and dental clearance before any radiotherapy. Fourth, the multidisciplinary decision mapping intent to extent: early disease to surgery with neck dissection, adverse features routing to adjuvant radiotherapy, unresectable or advanced disease to concurrent chemoradiation with palliative intent when performance status collapses. Fifth, response assessment and surveillance. Every step has a paperwork shadow — tumour board notes, consent recording the trade-offs — and the dental surgeon sits inside two of them: the diagnostic biopsy done properly, and the preradiotherapy dental clearance that decides whether the mandible survives the treatment.
How the exam frames it
Indian BDS papers ask for the stages of carcinogenesis, differences between benign and malignant tumours, grading versus staging, and the modalities of cancer treatment with definitions of neoadjuvant and adjuvant therapy. The viva layers on Indian causation: tobacco (smoked and smokeless) and areca nut dominate oral cancer aetiology, and national programme framing — the National Programme for Prevention and Control of Cancer, Diabetes, Cardiovascular Diseases and Stroke, with its oral cancer screening and tobacco-control arms — converts textbook aetiology into public-health answers. The slip to avoid: quoting a tumour marker as diagnostic; markers monitor, histology diagnoses.
Frequently asked questions
How does staging differ from grading in oncology?
Staging measures anatomical extent by TNM (how far the cancer has travelled), whereas grading assesses histological aggressiveness by differentiation (how abnormal the cells look) — staging drives treatment choices more strongly.
What are the three stages of carcinogenesis?
Initiation, an irreversible carcinogen-induced mutation; promotion, reversible proliferation of initiated cells by promoters; and progression, acquisition of invasive and metastatic properties.
What does neoadjuvant therapy mean and when is it used?
Treatment — chemotherapy or radiotherapy — given before definitive surgery to downstage locally advanced tumours, test chemosensitivity and permit less radical surgery.
Why is performance status assessed before chemotherapy?
Because patients with WHO/ECOG grade 3-4 status tolerate cytotoxic toxicity poorly and are generally offered supportive or palliative options instead.
Which gene is most commonly mutated in human cancers?
The p53 tumour suppressor, guardian of the cell cycle — disabled by mutation or, in HPV-associated cancers, by the viral E6 protein.