Computed Tomography Role in Limited-Stage Lymphomas: Could We Reduce the Dose of Radiation?

Lymphomas are the most frequent blood cancer. Current Lymphoma's guidelines recommend initial staging and interim surveillance computed tomography (CT) scan, repeated every 6-12 mo for the first 2 years (ys) after end of treatment. Recent studies show that patients receiving 8 or more CTs have a 2-fold increase in secondary malignancies. This risk is dose-dependent. Cumulative exposure in excess of 75mSv has been estimated to increase cancer mortality by 7.3%. At present, more than 80% Hodgkin's Lymphoma (HL) patients and more than 60% of NHL patients will be alive 5 ys after diagnosis. This percentage is higher in early stage disease (HL: 96 % overall survival (OS) at 5 ys; NHL: depends on the subtype, for DLBCL: 68-90 % at 5 ys). Considering this high survival rates and the demonstrated toxicity of radiation, avoiding CT scans overuse seems reasonable, especially in those with great chances of being cured.

Methods

A retrospective review of all biopsy-proven stage I-II HL and NHL diagnosed and treated at Hospital de Clínicas, Montevideo, Uruguay, from 1/1/2001 to 1/1/2013 was conducted. Data were obtained from our prospectively-intended database at Lymphoma Unit, and we expressed results with mean +/- SD and median using SPSS program. The cumulative effective radiation dose (CED) was calculated through standardized procedure-specific radiation dose levels. The primary objective was to analyze utility of interim / end of treatment body CT scan in detecting new areas of involvement and progression. Secondary objectives included number of CT performed, total radiation (mSv) received, utility of regular CT scanning in detecting preclinical relapse during follow-up.

Results

During this period, 73 patients were diagnosed stage I or II Lymphoma, 82% NHL and 18% HL. Most prevalent histologic subtypes were Nodular Sclerosis (9/13) and DLBCL (39/60). Median age at diagnosis was 55 years (15-82), with 34% aged <40; 56 % were female. Median follow-up was 36 months, with 53 patients with more than 1 year of follow-up.

At onset, 96% of patient had diagnostic CT, in 91% 2 or more regions were scanned and in 75% 3 or more. Sixty percent of patients were stage II; 42% had B symptoms and 16% were Bulky. A median of 20 mSv (3-26) was received at initial staging and a median of 15 mSv at the end of first-line therapy (0-26). Excluding those who died or were lost during the first 3 months, interim CT scan was done in 74 % (54/63); 4 patients showed progression, all at the initially involved site. Body CT scan did not detect new sites of involvement. At the end of treatment, CT scan was performed in 46 patients (all but 2 were body CT). No new site of involvement was detected; 67% of patients were in complete remission; 17% in partial remission; 6,5% stable disease and 8,7% in progression, all at the initially involved site. Median number of CTs at first year was 3,5 (1-7).

Twenty-nine patients completed at least 5 ys of follow-up; median CTs per patient was 6 (1-11) with a median of 100 mSv (3-175). NHL patients (n=60) had a median of 3 CT during first year with a median of 41 mSv (3-90). HL patients (n=13) had a median of 4 CTs (3-6) and a median of 58 mSv (40-80).

At 5 ys, 31 patients (42%) received more than 75 mSv.

Two patients relapsed in a new site. Both were detected clinically before CT was performed. Regular CT scanning did not allow to detect relapse before being clinically evident.

Discussion

Surveillance imaging in early stage lymphomas should balance early detection of progression and relapse versus the risk of secondary malignancies, especially in young and curable patients. Most early stage lymphomas respond well to therapy, and progression and relapse are usually located at the initially involved site.

In our study, body CT scan did not detect progression in new territories neither at interim evaluation nor at the end of therapy. Forty two percent of patients received a CED that doubles the risk of secondary malignancies. Considering this data, CT scan restricted to initially involved site may be sufficient for surveillance in limited-stage lymphomas, avoiding unnecessary radiation.