Gamma camera scans and pretreatment tumor volumes as predictors of response and progression after Y-90 anti-CD20 radioimmunotherapy.
OBJECTIVE
To evaluate two potential approaches to predicting site-specific patterns of recurrence after yttrium-90 ibritumomab tiuxetan radioimmunotherapy (RIT) for CD20+ B-cell Non-Hodgkin's lymphoma. These predictive methods may be useful in evaluating the utility of local intensification of individual nodal or extranodal sites using external beam radiotherapy.


METHODS
Records and images were evaluated for 20 patients previously treated with yttrium-90 ibritumomab RIT. Intensity of isotope uptake on the pretreatment two-dimensional antibody scans and maximal extent of tumor deposits found on computed tomography images of each anatomic site were correlated with response and subsequent patterns of recurrence or progression.


RESULTS
Our data failed to suggest a significant correlation between the site-by-site two-dimensional image intensity on the pre-RIT scan and the likelihood of response at those sites. In contrast, an analysis of pretreatment target volumes did correlate significantly with progression. A collective analysis of disease sites from all 20 patients found that 83% (10/12) sites of "bulky" (maximal diameter > or = 5 cm) disease displayed evidence of progression vs. 28% (26/93) of "nonbulky" disease sites containing gross disease but no area measuring >5 cm (p < 0.001). All patients with at least one site of bulky disease had initial disease progression occur at a bulky site, with a bulky site being the sole first site of progression in approximately 50%. In patients with only nonbulky disease sites, approximately one third progressed initially at an entirely new site of disease.


CONCLUSIONS
We conclude that we can use tumor bulk to establish a statistical hierarchy of likely tumor progression sites and use this pattern to direct the use of additional external beam radiotherapy to augment treatment.
Gokhale
Abhay S
AS
Department of Radiation Oncology, Cleveland Clinic Foundation, Cleveland, OH 44195, USA.
Mayadev
Jyoti
J
Pohlman
Brad
B
Macklis
Roger M
RM
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D018951:Antigens, CD20 / Q000276:immunology*; D018450:Disease Progression; D005260:Female; D015902:Gamma Cameras; D006801:Humans; D007205:Indium Radioisotopes; D016393:Lymphoma, B-Cell / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D016499:Radioimmunotherapy / Q000379:methods*; D011877:Radionuclide Imaging; D012008:Recurrence; D016896:Treatment Outcome; D015021:Yttrium Radioisotopes / Q000627:therapeutic use*
D000911:Antibodies, Monoclonal; D018951:Antigens, CD20; D007205:Indium Radioisotopes; D015021:Yttrium Radioisotopes; C422802:ibritumomab tiuxetan