| Research BackgroundAnaplastic large cell lymphoma(ALCL)is a large cell dominated T cell non-hodgkin lymphoma(NHL)characterized by high expression of CD30+,which is a relatively rare subtype of lymphoma.However,the imaging characteristics of ALCL on (18)~F-FDG PET/CT was rarely described and the role of (18)~F-FDG PET/CT in evaluating this disease has not been well established,possibly due to low incidence rate of the disease.To study the image manifestation of (18)~F-FDG PET/CT of ALCL will be helpful to further understand the biological characteristics of this disease,so as to better guide clinical practice.ALCL can be divided into anaplastic lymphoma kinase(ALK)positive ALCL and ALK-negative ALCL,and ALK-positive ALCL patients tended to have better prognosis than ALK-negative ALCL patients.The effect of ALK expression on the glucose uptake and invasion of the lesions is relatively rare in the literature.Further studies on this may help to understand the reasons for the different prognosis between ALK positive and negative patients.Although both B-cell ymphomas and T-cell lymphomas are belong to non-Hodgkin’s lymphomas,T-cell lymphomas generally respond poorly to chemotherapy and often have a poorer prognosis than B-cell lymphomas.However,unlike other T-cell lymphomas,ALCL responds well to chemotherapy and has a good prognosis,which is similar to the most common B-cell subtype lymphoma(diffuse large B cell lymphoma(DLBCL)).There might be some similarities in their biological behavior of ALCL and DLBCL.Analysis of their (18)~F-FDG PET/CT imaging features and the similarities and differences in response to chemotherapy may help to identify the reasons for the similarities in response to treatment and prognosis.Objective1.To study the (18)~F-FDG PET/CT imaging features of ALCL and to explore its biological characteristics;2.To investigate the influence of ALK expression on (18)~F-FDG PET/CT imaging,tumor invasion and treatment response.3.To study the similarities and differences of (18)~F-FDG PET/CT imaging features of ALCL and DLBCL,hoping to find the similarities in lesion metabolism and tumor invasion between ALCL and DLBCL,so as to explain the reason that the therapeutic effect superior to other T cell lymphoma.MethodsThe PET/CT imaging results of 58 cases of ALCL,including 37 ALKpositive patients and 21 ALK-negative patients,confirmed by pathology from November 2005 to August 2020 were retrospectively analyzed.The positive detection rate of (18)~F-FDG PET/CT imaging of ALCL,the maximum standardized uptake value(SUVmax)and the distribution of nodal and extranodal involvement as well as the response to chemotherapy were recorded and analyzed.Sixty cases of DLBCL pathologically confirmed between March 2017 and September 2018 were collected as the control group to compare baseline PET/CT imaging differences and their responses to chemotherapy.Data were analyzed by t test,Pearson chisquare test or Fisher exact test.Results(1)(18)~F-FDG uptake of ALCL and distribution characteristics of systemic lesions:ALCL lesions were demonstrated to be (18)~F-FDG-avid tumours with a mean SUVmax of 19.29±12.43 and the positive detection rate of (18)~F-FDG PET/CT for ALCL was 98.3%.nodal involvement occurred in 74.1%of patients,as did extranodal invasion.75.9%of ALCL patients were stage Ⅲ-Ⅳ patients at initial visit,while only 24.1%were stage Ⅰ-Ⅱ patients.(2)Comparison of ALK positive and ALK negative ALCL.The onset age of ALK-positive was younger than that of ALK-negative ALCL,except that there was no significant difference in gender,B symptoms and stage between the ALK-positive and ALK-negative groups.ALK expression affected (18)~F-FDG uptake of lesions and tumor invasion mode.Compared to ALK-negative lesions,a higher uptake of (18)~F-FDG was found in the ALK-positive lesions(SUVmax:25.4+15.2 vs.16.0+7.8,t=2.655,P=0.01).In terms of lesion distribution,ALK-positive ALCL was more likely to involve lymph nodes than ALK-negative ALCL(86.5%vs.52.4%,χ~2=8.127,P=0.004),while ALK-negative ALCL was more prone to involve the extranodal organs compared to ALK-positive ALCL(90.5%vs.64.9%,χ~2=4.583,P=0.03).The number of (18)~F-FDG-avid lymph nodes was 6.8±4.4 for ALK-positive ALCL,which was significantly higher than that(3.7±2.4)for ALK-negative ALCL(t=2.202,P=0.033),but there was no significant difference in the number of extranodal lesions between ALKpositive ALCL and ALK-negative ALCL(2.1±1.3 vs.2.0±1.4,t=0.112,P=0.911).In response to chemotherapy,there was no significant difference in complete response rates between ALK-positive and ALK-negative ALCL on (18)~F-FDG PET/CT at interim and end-of-treatment(17/21 vs.10/11,Fisher exact probability test,p=0.637).(3)Comparison between ALCL and DLBCL.Both ALCL and DLBCL showed significantly high uptake of (18)~F-FDG,and there was no significant difference in SUVmax between them(19.29±12.43 vs.20.90±10.73,t=0.751,P=0.454).ALCL and DLBCL showed many similarities in tumour stage,nodal involvement and the incidence of extranodal invasion(P>0.05).But there was obvious differences in extranodal invasion.The incidence of bone invasion was significantly higher than that of BLBCL(26/58 vs.9/60,χ~2=12.576,P=0.001),and the incidence of skin and soft tissue invasion was also significantly higher than that of BLBCL(13/58 vs.4/60,χ~2=5.931,P=0.015).On the contrary,the incidence of gastrointestinal invasion in BLBCL was significantly higher than that in ALCL(16/60 vs.5/58,χ~2=6.565,P=0.01).Meanwhile,the incidence of head and neck lymphoma in DLBCL patients was significantly more higher than that in ALCL(30/60 vs.17/58,χ~2=5.268,P=0.022).In response to treatment,there was no significant difference in complete response to chemotherapy between ALCL patients and DLBCL patients on (18)~F-FDG PET/CT during the interim and end-of-treatment(27/32 vs.27/35,χ~2=0.559,P=0.455).Conclusions1.The present study demonstrated that ALCL is a systemic (18)~F-FDGavid lymphoma,which often involves lymphnodes and extranodal organs at the same time.Also,ALCL Patients tend to be presented with later stages in their first visit.2.ALK expression has a significant influence on (18)~F-FDG uptake and lesion distribution of tumors,suggesting that ALK expression has a significant influence on the pattern of invasion.The poor prognosis of ALK negative ALCL may be related to more organ invasion,but the true reason may need further study to clarify.3.Except for the different parts involved in extranodal organs,ALCL and DLBCL have many similarities in (18)~F-FDG uptake,stage and incidence of nodal involvement and extranodal invasion,suggesting that the two lymphoma subtypes have some similarities in tumor aggressiveness and invasion mode,which may be related to the similarities in treatment response and prognosis between the two subtypes. |
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