====== Tumor Growth ======

**Tumor growth** refers to the **progressive increase in size and cellularity** of a neoplasm due to uncontrolled proliferation of abnormal cells. It is driven by genetic mutations, altered signaling pathways, and evasion of growth-suppressing mechanisms.

===== Growth Kinetics =====
  * **Gompertzian growth model**: Tumors grow rapidly in early stages, then slow as they outgrow their blood supply
  * **Doubling time**: Varies by tumor type and biological behavior
  * **Tumor burden**: Total number or volume of cancer cells present

===== Hallmarks of Tumor Growth =====
  * **Sustained proliferative signaling** (e.g., EGFR, KRAS, BRAF)
  * **Evading growth suppressors** (e.g., p53, RB)
  * **Resisting cell death** (e.g., BCL2 overexpression)
  * **Enabling replicative immortality** (e.g., telomerase activation)
  * **Inducing angiogenesis**
  * **Activating invasion and metastasis**

===== Key Molecular Pathways =====
  * **PI3K/AKT/mTOR**
  * **RAS/RAF/MEK/ERK (MAPK pathway)**
  * **EGFR signaling**
  * **MYC oncogene**
  * **Wnt/β-catenin**

===== Tumor Microenvironment (TME) =====
  * Stromal cells, immune cells, and blood vessels interact with tumor cells to promote:
    * Growth
    * Immune evasion
    * Angiogenesis
    * Therapy resistance

===== Imaging and Measurement =====
  * **Radiological assessment**: MRI, CT, PET
  * **Response criteria**: RECIST 1.1 (Response Evaluation Criteria in Solid Tumors)
  * **Biomarkers**: Ki-67 (proliferation index), LDH, PSA, CA-125, etc.

===== Therapeutic Implications =====
  * **Cytotoxic agents**: Kill proliferating cells (e.g., alkylating agents, antimetabolites)
  * **Targeted therapies**: Block growth-promoting pathways (e.g., EGFR, BRAF inhibitors)
  * **Immunotherapies**: Stimulate immune system to suppress or eliminate tumors
  * **Radiotherapy**: Damages DNA in rapidly dividing tumor cells

===== Related Topics =====
  * [[oncology:proliferation_index|Proliferation Index (Ki-67)]]
  * [[oncology:egfr_pathway|EGFR Pathway]]
  * [[oncology:angiogenesis|Angiogenesis]]
  * [[oncology:tumor_microenvironment|Tumor Microenvironment]]
  * [[oncology:targeted_therapy|Targeted Therapy]]
  * [[oncology:recist|RECIST Criteria]]