The Emergence of Theranostics in the Philippines: Overcoming Challenges and Bringing Hope.

Medical managements are becoming personalized while diseases are being understood at the molecular level. Nuclear medicine is one of the fields actively contributing to this development. In particular, theranostics, a combinatorial term for therapy and diagnostics, enables accurate imaging and subsequent targeted radionuclide treatment. Due to its high impact in healthcare, many countries have begun to offer Ga-68 PET/CT scans and Lu-177 therapies. The Philippines has followed suit through the initiative of this author and able support of the administration and staff of St. Luke's Medical Center. The Ga-68 DOTATATE and PSMA PET/CT scans became officially available in January 2018 while the first peptide receptor radionuclide therapy for neuroendocrine tumor and first PSMA radioligand therapy for prostate cancer occurred in May and June 2018, respectively. Amidst past, present, and future challenges, theranostics has emerged in the Philippines, offering hope to cancer patients in the country.

Utility of 99mTc-Sestamibi SPECT/CT in the Early Localization of Metastatic Parathyroid Carcinoma.

Parathyroid carcinoma is very rare, with only a few documented cases. Hence, metastatic lesions are infrequently documented on scintigraphic imaging. We present a case of a 63-year-old female presenting with elevated serum levels of ionized calcium and parathyroid hormone (PTH) who was referred to our department for a parathyroid scan with SPECT/CT. Parathyroid scintigraphy showed a focus of increased 99mTc-sestamibi uptake corresponding to a solid mass with calcification in the inferior pole of the right thyroid lobe; tracer retention was noted on delayed images. Incidentally, focal uptake was also seen in a soft tissue mass on the 7th right rib. The patient soon underwent total thyroidectomy, with biopsy revealing parathyroid carcinoma on the right lobe. A bone scan done 7 months after surgery confirmed the presence of metastatic bone disease. The concomitant detection of intrathyroidal and extrathyroidal sestamibi-avid masses on parathyroid scintigraphy should increase clinical suspicion of a metastatic process from parathyroid carcinoma.

SPECT-CT localization of Tc-99m methylene diphosphonate uptake in a subacute brain infarct on bone scintigraphy

Bone scan is a sensitive imaging procedure for cancer patients who are at high risk for bone metastases. Despite the high sensitivity, Tc-99m methylene diphosphonate (MDP) is not a specific tracer and its increased uptake may also be seen in extra-osseous areas. In cases where localization of extra-osseous sites of MDP uptake on planar imaging prove to be difficult, single photon emission computed tomography with computed tomography (SPECT/CT) may be useful. A known lung cancer patient was referred for whole body bone scan to detect bone metastasis. Planar images showed tracer accumulation in the left area of the head, suspicious for skull metastasis. SPECT-CT imaging of the head was done for further evaluation, which showed Tc-99m MDP uptake in the left temporoparietal lobe. Magnetic resonance imaging (MRI) of the brain was subsequently done, which showed a subacute brain infarct corresponding to the Tc-99m MDP-avid focus. Thus, SPECT-CT was helpful in proper anatomical localization of the focal Tc-99m MDP uptake in the head, which otherwise might have been easily mistaken for skull metastasis should only planar imaging was used.

Nuclear Medicine in the Philippines: A Glance at the Past, a Gaze at the Present, and a Glimpse of the Future.

While the introduction of radioactive tracers in the study of metabolic pathways has been well-documented in clinical thyroidology as early as 1924, the widespread utilization in other clinical specialties has been hampered by slow developments in radiation-detecting devices and in the production of appropriate radiopharmaceuticals, in addition to the morbid fear of radiation. In the Philippines, the first radioisotope laboratory was established in 1956. Ten years later, the Philippine Society of Nuclear Medicine was formed. Through the years, challenges were overcome, foundations were laid down, growth was encouraged, friendships with other organizations were built, adjustments were made, and rules were enforced. To date, there are approximately 58 nuclear medicine centers randomly distributed from north to south of the Philippines, 7 accredited nuclear medicine training institutions, 95 board-certified nuclear medicine physicians (a few of whom are also internationally recognized), and a regionally-indexed Philippine Journal of Nuclear Medicine. Qualifying examinations for technologists were also recently instated. International relations are constantly strengthened by sending trainees abroad and accepting foreign trainees here, as well as participating in conferences and other endeavors. While the cost of putting up nuclear medicine centers in the Philippines is still prohibitive, it should not pose too much of a constraint as there are foreign and local parties willing to help. With appropriate instrumentation, targeting radiopharmaceuticals and trained human resources, nuclear medicine can indeed contribute much to health care delivery.

The first MIBG therapy in the Philippines

Neuroblastoma is an embryonal tumor of children that frequently presents with metastases. Our patient is a 6-year-old girl who was diagnosed to have neuroblastoma with diffuse metastatic disease throughout the skeleton as seen in her 123I-MIBG scan in the United States. 18F-FDG PET/CT scan was done in the Philippines after chemotherapy and gene therapy, and before 131I-MIBG therapy. No additional lesions were seen on PET.  131I-MIBG was then performed and an 131I-MIBG with SPECT/CT thereafter, which showed an increase in size and extent of the lesion in the head and a decrease in number of the skeletal metastases. New 131I-MIBG-avid posterior cervical lymph nodes were also localized through SPECT/CT. For this patient, a follow-up 123I/131I-MIBG scan would be more cost-effective in assessing response to therapy. Sectional imaging may be done to obviate the need for sedation of this young patient.

Hybrid 18F-FDG PET with low- and high-dose CT for malignancy screening

The primary objectives of this retrospective study were to determine the cancer detection rate of PET/CT in this institution and to compare the sensitivity and specificity of low-dose PET/CT to that of PET with high-dose CT. Three hundred sixty-seven (367) patients with unremarkable history, family history of cancer, symptoms or abnormal diagnostic tests, and with follow-up studies were included. PET/CT and histopathology results were noted. Individual and overall cancer detection rates, as well as sensitivities and specificities for each subgroup, were computed. Overall cancer detection rates was 22.3%, for low-dose PET/CT was 17.9%, and for high-dose PET/CT was 24.4%. Using the chi squared test of independence, no statistically significant difference was found between the calculated sensitivities and specificities of low- and high-dose PET/CT across all patient groups. Using the Mantel-Haeaszel chi squared test, a statistically significant association between the subindication for malignancy screening and PET/CT results was established with subindications pointing to a higher suspicion for malignancy having a higher probability of detecting a malignancy. Therefore, high-dose PET/CT as a screening test would be advised for high-risk patients and low-dose PET/CT would be recommended because of its similar accuracy but lower radiation exposure.

The role of 18F-FDG PET in the evaluation of treatment for lymphoma: Philippine setting

PET is essential for the post-treatment assessment of lymphomas because a negative PET scan after treatment is required for a complete remission and curative outcome. Functional imaging with 18F-FDG PET enables evaluation of the early metabolic changes rather than the moprphologic changes of the lymphoma occurring later. Among 186 patients diagnosed with Hodgkin's Disease or Non-Hodgkin's Lymphoma who were referred to the PET Center in this institution from April 2002 to June 2010, 35 patients were included in this study. All 14 patients who only had end-of-chemotherapy scans without midcycle scans had no tumor recurrence on subsequent scan/s, with a median follow-up of 17.5 months. Of the remaining 21 patients, 11 patients had positive studies, 9 had negative studies and 1 had an indeterminate study of the midcycle scans. All the patients obtained similar results on the subsequent scans, excluding 5 with no follow-up scans, with median follow-ups of 13 months for the PET-positive patients and 23 months for the PET-negative patients. These results support the strong prognostic value of PET for aggressive lymphomas, whether the imaging is performed at the end of therapy or after only a few cycles of chemotherapy. PET has consistently been shown to identify positive respondents with higher survival probabilities and longer progression-free survival periods from non-responders on subsequent scans.

The use of SPECT-CT in determining 90Y microspheres distribution post selective internal radiation therapy

Hepatocellular carcinoma and metastatic colorectal carcinoma are amongst the more common causes of cancer-related mortality worldwide. Selective internal radiation therapy (SIRT) with 90y microspheres is usually indicated in patients with nonresectable status and extensive colorectal liver metastases that are refractory to chemotherapy or target therapy. Several examinations, including CT, MRI or PET, serum chemical analyses, hepatic angiography and liver-lung shunting study with Tc-99m MAA, are done to ensure appropriateness and safety of therapy. Herein, three cases (two with hepatocellular carcinoma and one with metastatic colorectal cancer), which qualified for SIRT and underwent SPECT-CT, are presented. All of them underwent the necessary pre-therapy work-ups. The CT and PET-CT scans identified the hepatic lesions. The blood tests showed nearly normal hepatic and renal functions, except for the third case with elevated bilirubin level. The hepatic angiograms revealed no significant gastrointestinal shunting. The liver-lung shunting studies computed 10% hepatopulmonary shunt. Together with the patient with an elevated bilirubin level, they received a reduced dose of 90Y microspheres by 20%. After SIRT, bremsstrahlung planar imaging and SPECT-CT were performed to localize the distribution of the 90y microspheres, the findings of which correlated well with the results of the pre-therapy scans. The use of SPECT-CT is recommended for better anatomic localization and functional correlation.