The Impact Of Radiotherapy Field Size On Survival Of Patients With Early Stage Diffuse Large B Cell Lymphomal

Purpose : To study whether the radiation field size can be safely reduced in the high-precision era of radiotherapy by analyzing the impact of the radiotherapy field size guided by the functional molecular imaging(PET/CT)on the survival of the patients with early stage diffuse large B cell lymphoma(DLBCL)under the combined treatment modality of R-CHOP plus radiotherapy.Patients and Methods: 57 patients had been chosen from the lymphoma data pool treated in the Hunan cancer hospital from January 1,2011 to December 30,2015.All patients were early stage DLBCL with at least one PET-CT scan during the treatment.The data of target size,remission status after chemotherapy,age,sex,bulky Disease,IPI score,LDH,Radiotherapy parameters and chemotherapy regimes had been collected and factors related to survival were analyzed retrospectively.57 cases with detailed radiotherapy plan parameters were grouped according to the radiation field sizes of superior and inferior boundary of the CTV extention(superior CTV extension ≤4.74 cm,28 cases;>4.74 cm,29 cases;inferior CTV extension≤8.5cm,37 cases;>8.5cm,20 cases).Their respective OS,PFS,DMFS,late and early toxicity and patterns of recurrence after radiotherapy had been compared.In addition,the impactof chemotherapeutic remission status(CR/PR)on survival with different superior and inferior CTV extension were further analyzed.Results:The median follow-up time is 31.1 months(9.36-74.22months),the overall local control rate is 96.5%(55/57),distant recurrence rate is 14%(8/57);5-year local control rate is 91.1%,and 5-year distant recurrence rate is 15.3%;total 5-year OS,PFS,DMFS are 85.1%,74.8%,81.1%;The median follow-up time is 30.2 months of CTV≤4.74 cm group and the CTV>4.74 cm group’s median follow-up time is 32.8 months.The5-year OS,PFS and DMFS are 96.3% and 77.1%(P=0.135),96.3% and59.5%(P=0.013),and 96.3% and 69.3%(P=0.038)respectively;The5-year OS,PFS,DMFS for inferior boundary group CTV≤8.5cm and CTV>8.5cm are 94.6% and 73.9%(P=0.16),77.8% and 68.9%(P=0.362),77.8% and 83.8%(P=0.938).The superior CTV extension size has no impact on OS with both CR and PR cases(P=0.893).Multivariate analysis showed that the independent prognostic factors of OS are LDH(P=0.028);The independent prognostic factors for PFS are superior CTV extension(P=0.039),number of chemotherapy cycle(P=0.003);The independent prognostic factors for DMFS are gender(P=0.023),the location of tumor(P=0.012)and IPI score(P=0.025);Most of the toxicity of >2 grade are found in the group of CTV>4.74cm(P=0.016).Total 10 patients had been relapsed,among them,2 patients of local regional recurrence and 8 distant recurrence.There is no marginal recurrence.Local recurrence occurred only in the group of CTV>4.74 cm,and distant recurrence was found in 2/8(25%)in CTV≤4.74 cm group,however 6/8(75%)in CTV>4.74 cm group.The difference of toxicity and recurrence rate had no statistical significance between sub-grouping in inferior CTV extension(P > 0.05).Conclusion: Both the superior and inferior radiation field size could be reduced to CTV≤4.74cm(INRT≤5cm)and CTV≤8.5cm(INRT≤8cm)without compromising survival and increasing relapses for early stage DLBCL in the real world of treatment,in the contrary,the side effects related to radiation would be reduced.