Radiation therapy is one of the main treatment methods for cancer. Machine learning can be used in all aspects of clinical practice in radiation therapy, including clinical decision support, automatic segmentation of target volumes, prediction of treatment efficacy and side effects. Despite the challenges of lacking structured data and poor interpretability of models, the application of machine learning in radiotherapy will become increasingly profound and extensive. This review contains three aspects: introduction of machine learning, the clinical application of machine learning in radiotherapy, challenges and solutions.

Objective To confirm whether or not let-7b and miR-199a were significantly associated with malignant melanoma growth and proliferation. Methods An over -expression plasmid and an inhibitor, which targeted on let-7b and miR-199a, was constructed. B16F10 cells were divided into seven groups: control group, let-7b plasmid group, miR-199a plasmid group, empty plasmid group, let-7b inhibitor group, miR-199a inhibitor group, inhibitor control group. Foreign gene was transfected into B16F10 cells, let-7b and miR-199a expression were validated from RNA level, protein level and cell level. Results The relative let-7b or miR-199a gene expression of the let-7b plasmid group (3.8776±0.1372)and miR-199a plasmid group (2.8660±0.2821)were significantly higher than control group (P＜0.05), the relative let-7b or miR-199a gene expression of the let-7b inhibitor group (0.2057±0.0263) and miR-199a inhibitor group(0.2656±0.0253) were significantly lower than control group(P＜0.05). The cyclinD1 expression of the let-7b plasmid group(2.023±0.315) and let-7b inhibitor group (1.857±0.377) were significantly higher than control group (0.997±0.041) (P＜0.05), whereas, the Met expression of themiR-199a plasmid group (5.19±0.309) and miR-199a inhibitor group (4.87±0.044) were significantly higher than control group (2.2±0.198) (P＜0.05). The let-7b plasmid group and miR-199a plasmid group B16F10 cell growth rate were slower than control group, especially on the third day after transfection, the growth rate gradually dropped to the lowest value (P＜0.05). In addition, the apoptosis rates of the let-7b plasmid group and miR-199a plasmid group reach to (11.8±1.19)% and (11.3±1.59)%,which were significantly higher than control group (P＜0.05). Conclusions let-7b and miR-199a may be a negative regulator on the B16F10 cell growth and proliferation.

Objective To study the influence of let-7b on cell proliferation and aerobic glycolysis of human melanoma cell A375.Methods Transfect A375 cell line with hsa-let-7b oligonucleotide or antisense.Glucose and lactate in medium were determined by spectrophotometry at 24 h and 48 h time point after transfection.The cell proliferation was determined by methylthiazol tetrazolium (MTT) assay.Results Over expression of let-7b in melanoma cell reduced cell proliferation notably,compared to the other groups by MTT(P ＜0.05).However,the glucose consumption and lactate production differences were not observed during 24 h or 48 h ( P ＞ 0.05 ),the blank control group transformed about 57％ and 43％ glucose to lactate during 24 h and 48 h.Conclusions Melanoma cell line A375 has notably aerobic glycolysis hallmark,let-7b could inhibit proliferation of melanoma cell line A375,but it may has no influence on glucose metabolism.