PET in oncology: The Philippine setting

Full text: Cancer ranks third in the lead cause of morbidity and mortality in the Philippines. Positron Emission Tomography is one of the new imaging modalities used in the multidisciplinary approach to cancer treatment. It has the ability to stage disease and determine the presence of viable tumor cells. A number of research studies have shown the increased sensitivity and specificity of PET in diagnosing and staging different types of cancer. It is highly sensitive and specific particularly for lung, breast, colorectal, lymphoma, melanoma and head and neck cancers. Studies have also shown its usefulness in detecting unknown primaries, and in cancer screening as well. This study was therefore conducted to give a descriptive scenario of how PET was utilized in the field of Oncology during its first year of existence in the Philippines. The study population consisted of 368 patients who underwent whole body FDG-PET scanning from January 2002 to May 2003. The protocols performed were adapted to the patient's cancer type and clinician's indication. Among all the PET procedures done during the said period, whole body FDG-PET scanning for cancer patients emerged as the most commonly requested procedures (83%). PET referrals came from different medical specialties and more than half of them came from Medical Oncologists accounting for 53% of all referrals. The PET centre has also evaluated patients with different cancer types and the cancer of the gastrointestinal tract was the source of the greatest number of referrals (16%). Other frequent sources of referrals were patients with breast, lung and head and neck cancers. Cancer patients were evaluated for different indications and the two most common reasons for these referrals were to evaluate the recurrence and to determine extent of disease. The evaluation of recurrent malignant disease is a problem frequently encountered with anatomic/structural imaging and almost 83% of the 115 patients referred showed hypermetabolic foci in the suspicious areas. 71% of the patients referred for staging showed extensive disease. 60 patients who underwent prior treatment were also referred for PET scanning and 28% of these showed good response to therapy. A number of patients with palpable masses and/or masses seen by other imaging modalities were sent for a PET scan to determine their 'malignant potential' and this accounted for the second most common source of referrals. 42% of these masses turned out to be hypermetabolic, 19% showed other foci of hypermetabolism and the rest were normal. A total of 26 patients with cancer metastases but without any primary tumors were also referred for PET scanning. 96 percent of these patients showed hypermetabolic foci. However, only 8 patients with abnormal findings were biopsied in our centre. Out of the 8 patients, 6 were proven to be the primary malignant disease while the rest were benign. Patients were also sent to us for cancer screening and we were able to detect hypermetabolic lesions in 9 out of the 27 patients. In conclusion, the ability of PET to stage malignant disease, assess for recurrent malignant disease, evaluate therapeutic response, locate unknown primaries and determine the malignant potential of unknown masses makes it a very useful ancillary tool in the diagnosis and treatment of cancer patients. (author)