Predictive Value of let-7a for Cancer Cell Repopulation between Chemotherapy and Long-Term Survival: A Prospective Study

Repopulation during radiation is a classic theory in radiobiology. The long intervals between cycles of chemotherapy provide better micro-circumstance than radiation for the repopulation of cancer cells. Patients with inoperable stage III and stage IV lung cancer were enrolled prospectively. Peripheral blood and tumor tissues were obtained before treatment and each cycle of chemotherapy to detect the serum let-7a expression and Ki-67 index. Fifty-two consecutive consenting patients were enrolled prospectively. The median follow-up was 13 months (range: 2-62 months). A strong correlation was found between the Ki-67 index and serum let-7a before treatment (r =-0.667,