Central lymphatic irradiation for stage I-III follicular lymphoma: Report from a single-institutional prospective study

Purpose: This study was undertaken to update our experience with follicular lymphoma treated with central lymphatic irradiation (CLI). Methods and Materials: A total of 47 patients were treated with CLI between January 1993 and March 2000 in a prospective manner. CLI consisted of mantle, whole abdomen, and pelvic radiation fields with a 1-month break after each field. Each field was treated to 3000-3060 cGy at 150-180 cGy per fraction followed by a boost dose of 900 cGy to the areas with gross disease. The median age was 52 years (range: 29-73 years). There were 29 males. The diagnoses were as follows: follicular small cleaved-cell lymphoma, 23 patients; follicular mixed-cell lymphoma, 19 patients; follicular large-cell lymphoma, 5 patients. Ann Arbor stages were as follows: I, 5 patients; II, 14 patients; and III, 28 patients. The International Prognostic Index (IPI) categories were as follows: 0, 14 patients; 1, 24 patients; and 2, 9 patients. M. D. Anderson Tumor Score was as follows: 0, 14 patients; 1, 18 patients; 2, 9 patients; 3, 4 patients; 4, 1 patient; and unknown, 1 patient. Two patients had abnormal LDH levels, and 11 patients had β2M levels >2 mg/dL. Gender, pathology, stage, IPI, Anderson Tumor Score, β2M, and number of disease sites were examined for significance in freedom from progression (FFP) by univariate analyses. Results: The median follow-up was 54 months (range: 8-93 months) for the 45 surviving patients. Every patient achieved a complete response, except for 1 patient whose lymphoma progressed to diffuse large-cell lymphoma during treatment. The 5-year overall survival and FFP were 94% and 53%, respectively. No failure has yet been observed beyond 55 months of follow-up with 13 patients at risk. Patterns of failure were as follows: within the radiation field, 10; outside the fields, 4; and both, 2. Of the seven variables investigated, β2M >2 mg/dL and IPI >1 were the only significant adverse prognostic factors for FFP (p = 0.023 and 0.046, respectively). Conclusions: CLI is well tolerated and seems to achieve durable FFP in about half of the patients with Stage I-III follicular lymphoma. Most of the experiences with CLI come from the treatment of Stage III disease and are very similar to our previous experience with combined modality treatment. Whether a plateau in FFP can be maintained beyond 5 years remains to be seen.