Early in vivo detection of metabolic response: a pilot study of 1H MR spectroscopy in extracranial lymphoma and germ cell tumours.

Monitoring therapeutic efficacy is essential in oncological practice. We have investigated the feasibility of using proton (1)H MR spectroscopy (MRS), localized to malignant lymphoma and germ cell lesions outside the cranial cavity, to monitor tumour metabolism in vivo during chemotherapy treatment. (1)H single voxel MRS, (stimulated echo acquisition mode, repetition time/echo time=2000/20 ms) was performed prior to treatment in patients with lymphoma or germ cell tumours, and during the first cycle of chemotherapy. Patient response was assessed by independent clinical follow-up at a median of 57 days (range 44-93 days) post-treatment. All 12 non-cystic lesions scanned showed a signal assigned to choline-containing metabolites (tCho); 9 were scanned both pre- and post-treatment. Changes in the tCho:water ratio following treatment were found to predict subsequent patient response. In seven of these nine patients, the tCho:water ratio decreased in the first post-treatment scan, and all subsequently achieved a partial response to treatment. In the remaining two patients, both of whom progressed on treatment, the tCho:water ratio did not change significantly. Normalized to pre-treatment values, the non-responder group values (1.07 and 0.97) were clearly distinct from the responder group, whose values ranged from 0.43 to below detection level. To our knowledge, this is the first report of (1)H MR spectra from these tumour types and sites. These preliminary results indicate that metabolite signals can be detected using (1)H MRS in these tumour types and locations, as has already been established in the brain, breast and prostate. Moreover, the differential changes observed in the tCho region of the spectrum suggest that (1)H MRS could provide an early and sensitive indicator of metabolic response to chemotherapy.