31-P MR spectroscopy and MRI of a testicular non-Hodgkin lymphoma recurrence to monitor response to irradiation. A case report.

PURPOSE: To monitor the metabolic changes during the radiation treatment of a recurrence of a high malignant non-Hodgkin lymphoma (NHL) of the left testis. PATIENTS AND METHODS: A 76-year old patients who presented a diffuse centroblastic high malignant NHL recurrence in the left scrotal sac was examined with 31-P magnetic resonance spectroscopy (MRS) and proton magnetic resonance imaging (MRI) before, during and after megavoltage radiotherapy to a total dose of 56 Gy. RESULTS: The 31-P MRS spectrum of the tumor showed before starting irradiation, intensive phosphomonoester (PME) and phosphodiester (PDE) signals that overlapped the inorganic phosphate (Pi) signal. After 26 Gy irradiation, the Pi peak appeared and revealed an intratumoral pH of 7.08 very close to that in the normal testis (pH of 7.02). After 56 Gy the tumor disappeared and a complete remission was achieved. CONCLUSIONS: 1. 31-P MRS is sensitive to the changes in the tumor metabolic activity after irradiation with a dose of 26 Gy. 2. Pi and PME peaks could be good pathological markers in the steady-state response to irradiation. 3. MRI could confirm the radiation induced tumor regression and the achieved clinical complete remission.