Etiology Screening of Cancer

Epidemiology of Cancer

According to the World Statistics, Cancer incidence in males is Prostate > Lung > Colo-Rectal Cancer, whereas in females, breast cancer is seen most commonly followed by lung cancer and then colorectal cancer.

Cancer-related Deaths in males are most commonly due to lung cancer, shortly followed by prostate and colorectal cancer(CRC). In females, cancer-related deaths are most commonly due to Lung cancer, followed by Breast and lastly by CRC.

According to Indian Statistics, Cancer incidence is the highest in Breast > Lip/oral cavity >  cervix > lung > CRC. Lip/oral cancer is most common in males, and breast cancer is the most common in females.

Cancer overall is the 2nd most common cause of death, after CV diseases. Tobacco is the single most important preventable cause of death in India. Age is the single most important risk factor for cancer. About two-thirds of cancers are seen in the older population.

Cancer Trends                

Overall, cancer incidence is increasing in the developing world due to longevity and adoption of the Eastern diet, physician inactivity, and tobacco use. Overall, an increase in breast and uterine cancer is caused by a decrease in fertility rate and obesity. 

Lung cancer is decreasing in males faster than in females due to a decline in the smoking habits of the male population.

Overall, a decrease in prostate cancer due to early detection by PSA screening is seen. but an increase in advanced prostate cancer rates. CRC incidence is decreasing but increasing in adults over the age of 65 years. 

HCC incidence stabilized in males but increased in females (due to the HCV/opioid epidemic in Western countries.

Etiological Agents of Cancer

1. Smoking: It Causes 30% of all Cancer deaths. The overall prevalence of smoking is decreasing. Tobacco carcinogens form covalent bonds with DNA, causing miscoding/mutations. Cigars are worse than cigarettes as the Tobacco is just wrapped without filters. E-cigarettes (vaping) have some long-term risks as well.
2. Environmental/Lifestyle factors: Obesity and decreased physical activity.
3. EtOH: HCC, upper aerodigestive tract, esophagus, CRC, breast
4. Food: Smoked, salted, pickled foods consumption in excess can cause Stomach cancer
   • Red Meat can cause colorectal cancer(CRC)
5. Infectious Agents:

6. Physical Factors: UV light is a risk factor for Skin Carcinoma.
7. Inflammation caused by
   • GERD - Esophageal cancer
   • Liver cirrhosis - Liver (HCC)
   • Chronic pancreatitis - Pancreatic cancer
   • Gallstones, porcelain GB - GB cancer
8. Chemicals
   • Silicosis, Asbestosis - Lung, mesothelioma
   • Rn, Ni, Ar, Cr - Lung
   • Aromatic amines - Bladder
   • Cadmium - Prostate
   • Benzene - Leukemia
   • Aflatoxin, vinyl chloride - (Liver Vinyl chloride - angiosarcoma of the liver)
   • Estrogen (HRT) - Breast, endometrium
   • Androgen - Prostate
   • Immunosuppressants - NHL
   • Chemotherapy (alkylating agents, platinum agents, anthracyclines) - MDS, leukemia, bladder cancer (CYC)

Tumor Markers

Cancer Prevention and Screening - Breast Cancer

Breast cancer screening recommendations:

• Female should Consider annual MRI (superior to MMG) in young risk (in lifetime risk ≥20%;  eg, family history, BRCA mutations, prior thoracic RT)
• Chemoprevention: Age ≥35 + Risk factors (ADH/ALH/LCIS, Thoracic RT < 30y, 5y risk ≥3% (NCI/BCRAT) or 10y risk ≥5% (IBIS) -> AI vs SERMs (Avoid and Raloxifene if pre-menopausal)
• SERMs increase TE events (C/I if H/o VTE) + Tamoxifen increases the risk of endometrial Cancer
• Breast Cancer screening recommendations in special situations:
  • BRCA ½ mutation carriers or untested FDRs: MMG + MRI (Q1Y) and CBE (Q6 - 12months)
    • Start based on the age of the youngest affected  family member (or) Age ≥25
• Additional considerations in BRCA ½ mutations                               
  • Consider rrBLM (decrease breast cancer by ≥90%)
  • Consider rrBSO (decreased ovarian Cancer by ≥85 - 90%)
  • Breast Cancer screening - yearly CBE (Age ≥35) + MMG (Age ≥40)
  • Prostate cancer screen - yearly DRE + PSA (Age ≥40)
  • H/o Thoracic RT: MMG + MRI (Q1Y)and CBE (Q6-12m)
    • 8-10 yr after RT of Age ≥40
  • Hx of LCIS or ALH/ADH: MMG (Q1Y) and CBE (Q6-12 months)

Cancer Prevention and Screening - Cervix Cancer

• Cervix Ca Prevention
  • Gardasil (6,11,16,18) and Cervarix (16,18) - contain type-specific L1 (capsid protein)
  • Recommended: 9 - 26 years (best if given before beginning sexual activity)
  • Dose: 0,6-12m (if ≤14 years) and 0,1-2 months, 6 months (if  ≥15 years). No booster.
• Screening methods: Pap (Conventional, LBC), HPV DNA testing, VIA/ VILI
  • Screen even if vaccinated, in case of the positive screen - Colposcopic Bx
  • Start @ age ≥21. Pap Q3y (if Age<30 or Pap+HPV CNA Q57 (if age ≥30)
  • Stop if age ≥65 + negative screening in last 10 years (or) TH + no residual cervix (if done for benign causes)

Cancer Prevention and Screening - Colo-Rectal Cancer

• CRC prevention: Polypectomy, removal of adenomatous polyps
• USPSTF: Adults 50-59 years with 10%>10year CV risk->ASA x 10 years
• Screening modalities:
  • Colonoscopy (Q10y), flexible sigmoidoscopy or CT colonography (Q5y), stool-based tests (guaiac Q1y or DNA based Q3y) - stool-based tests cannot detect adenomas.
• When to screen:
  • Average risk: Age ≥45 (ACs, ACG) or ≥ Age 50 (USPSTF) - till age 75
  • Average risk = No personal h/o adenoma or CRC, no personal H/o IBD & no family H/o CRC
  • FDC + CRC: Age ≥40-45 or 10y before earliest diagnosis in FDR

Cancer Prevention and Screening- Prostate Cancer 

• Prevention: Se and Vitamin E are not beneficial. Finasteride (Age ≥55 ) can decrease risk.
• Screening: PSA testing controversial
  • ACS: consider if age ≥50 or Age ≥40-45 (if FDR with Prostate Cancer)
• Lung cancer
  • Prevention: Smoking cessation is the most effective way to prevent lung cancer
  • Screening: Annual LDCT if age 50-80 + ≥20 PY(current smokers/stopped <15 years)
• Skin cancer: Sunscreens decrease the risk of non-melanoma skin cancers and cutaneous melanoma.
• Multivitamins can reduce the risk of cancers (overall) in people aged > 50 

To read about the Performance Status Tools and the Karnofsky Performance status (KPS) and other important topics related to cancer screening, log in to the PrepLadder app and watch the video on the ‘Etiology and Screening of Cancer' topic in the SS medicine section of the app. 

Also Read: Cancer Therapies - Types And Basic Principles

Frequently Asked Questions:

Question: What is the single most important preventable cause of death in India?

Answer: Tobacco

Question: The decrease of what factor causes an increase in breast and uterine cancer?

Answer: A fertility decrease causes an increase in breast and uterine cancer. 

Question: What is the most common cause of Skin Cancer?

Answer: UV light exposure

Hope you found this blog helpful for your NEET SS Medicine Oncology preparation. For more informative and interesting posts like these, keep reading PrepLadder’s blogs.