Patterns of metastases progression- The linear parallel ratio

Area of Science:

• Oncology
• Medical Imaging
• Cancer Metastasis

Background:

• Metastatic progression is modeled by linear and parallel spread patterns.
• Linear model: genetic alterations accumulate in primary tumor before metastasis.
• Parallel model: disseminated tumor cells spread early, with independent selection at ectopic sites.

Purpose of the Study:

• To propose a simple method to differentiate between linear and parallel metastatic progression models.
• To analyze metastasis size distribution to infer the predominant metastatic route.

Main Methods:

• Retrospective analysis of chest CT scans from 503 cancer patients with lung metastases.
• Measurement of metastasis number and largest diameters.
• Calculation of the linear/parallel ratio (LPR) based on metastasis size similarity.

Main Results:

• A total of 12,887 metastases were analyzed across nine malignancy types.
• Overall median LPR was 0.71, indicating a predominantly linear pattern.
• Thyroid, pancreas, and prostate carcinomas showed a median LPR of 1 (purely linear).
• Renal cell carcinoma, melanoma, colorectal, breast, bladder, and sarcoma showed decreasing LPR values, indicating increasing parallel progression.

Conclusions:

• Metastatic spread of thyroid, pancreas, and prostate tumors is predominantly linear.
• Kidney, melanoma, colorectal, breast, bladder, and sarcoma exhibit both linear and parallel spread, with a greater dominance of the parallel route in this order.
• These findings can help predict tumor features and evaluate metastatic origin.