Fracture Rates in Men With Non-Metastatic Prostate Cancer on Androgen Deprivation Therapy With or Without Anti-Osteoporosis Treatment

Introduction: Androgen deprivation therapy (ADT) decreases bone mineral density and increases osteoporotic fracture (OsteoFx) risk. Hypothesis: To assess OsteoFx incidence most predictive of future OsteoFx among men with prostate cancer on ADT. Methods: 4370 electronic medical records were reviewed of adult men with prostate cancer on cancer therapy +/- anti-osteoporotic therapy (Anti-OsteoRx) from 2011–2019. Cancer therapy included ADT (anti-androgens, GnRH agonists & antagonists, orchiectomy) and supplemental cancer therapy (SupplRx) (prostatectomy, brachytherapy, radiation, immunotherapy, and chemotherapy). Anti-OsteoRx included bisphosphonates, denosumab, and parathyroid hormone analogs. Patients with other cancers within 5 years of initial visit, metastasis or traumatic fractures were excluded. Retrospective analysis was done to determine baseline characteristics, type and duration of ADT, Anti-OsteoRx, SupplRx, and OsteoFx incidence. Results: Fracture rate subgroups: • ADT only - Anti-OsteoRx 37/ 374 fractured (9.89%) • ADT only + Anti-OsteoRx 10/52 fractured (19.23%) • ADT + SupplRx + Anti-OsteoRx 2/19 fractured (10.53%) • ADT + SupplRx + Anti-OsteoRx 13/170 fractured (7.65%) Comparing fracture rates between subgroups: • Comparing ADT only +/- Anti-OsteoRx, statistical significance was observed with higher fracture rate in patients taking Anti-OsteoRx (19.23% vs. 9.89%, p < 0.044) • Comparing ADT + SupplRx +/- Anti-OsteoRx, no significant difference in fracture rates due to small number of fractures Comparing combined subgroups: • ADT +/- SupplRx + Anti-OsteoRx 12/71 (16.9%) fractured • ADT +/- SupplRx - Anti-OsteoRx 50/544 (9.19%) fractured • Statistically significant between groups fracture rates was observed (p= 0.042) in patients treated with Anti-OsteoRX. Discussion: Patients receiving Anti-OsteoRx, regardless of their prostate cancer therapies, had higher rates of fractures (16.9 vs. 9.19%, p= 0.042) due to their being selected for therapy based on greater clinical risks. The Anti-OsteoRx group had a higher percentage of glucocorticoid listed as a historical medication (26.8 vs.15.3% vs, p= 0.023), glucocorticoids administered (50.7 vs. 30.3% p=0.001), and anticonvulsants and proton-pump inhibitor use (45.1 vs. 26.5%, p= 0.002). Conclusion: Higher fracture rates were observed in patients on Anti-OsteoRx that could be related to their being selected for treatment based on risk factors known to be associated with osteoporosis. Limited Anti-OsteoRx use in our study is possibly related to lack of standardized guidelines for prevention of osteoporotic fractures in prostate cancer patients. OsteoFx risk assessment utilizing CRF, DXA, and FRAX may prevent fractures in these high-risk patients. Further long-term prospective studies to address these unresolved queries are warranted.

Radioactive Iodine Resistant Papillary Thyroid Cancer “Redifferentiated” With Dabrafenib

Background: Differentiated thyroid cancers (DTC) make up 95% of all thyroid cancers. Radioactive iodine therapy (RAI Rx) is an integral part of DTC management. However, 5-15% of DTC and 50% of metastatic DTC become resistant to RAI Rx and carries a 10-year survival of only 10%. One of the newer therapeutic options target “redifferentiation” of the tumor using RAI sensitizers, notably with short-term use of tyrosine kinase inhibitors (TKI). Clinical Case: A 62-year-old women with a 3-year history of Papillary TC s/p surgery (Sx) and 175 mCi RAI presented to establish care and was found to have bulky palpable disease in her left lateral neck. Imaging showed bilateral enlarged lymph nodes in the neck and multiple bilateral pulmonary nodules. Her stimulated thyroglobulin (TG) level was 5341 (1.59 - 50.03 ng/dL) with negative TG antibodies. Bone scan showed no evidence of bone mets. She underwent repeat neck dissection (49 positive lymph nodes) and was BRAF V600E positive. Post-Sx her non-stimulated (NS) TG was 340 ng/dL (0.00 - 41.00 ng/mL) and she received 200mCi RAI Rx with post-Rx whole body scan (WBS) showed uptake only in the thyroid bed. Imaging 6 months later showed stable lung nodules but increase in lymphadenopathy in the neck and her NS-TG was 181 ng/dL. She received 250 mCi of RAI Rx, 10 months after the first dose. Post Rx WBS again showed uptake only in the neck. Her non-stim TG, 9 months later was still high at 130 ng/dL. Given the discordant imaging and TG findings, functional imaging was done which showed multiple avid lesions in bone and lymph nodes confirming the diagnosis of radioiodine-refractory (RAI-R) DTC. Given BRAF V600E positive status, she received Dabrafenib 150 mg PO BID for 6 weeks followed by RAI 300 mCi. Post-RAI WBS showed extensive uptake in base of skull, sternum, cervical spine and right supraclavicular area. Six months post Dabrafenib and RAI, her NS-TG had come down from 130 to 25.7 ng/dL and imaging showed stable structural disease. Her TG levels and imaging have remained stable over the last 18 months indicating both biochemical and structural response to Dabrafenib. Conclusion: The goal of TKIs in redifferentiation of RAI-R DTC is to target specific molecular mechanisms to render the tissue sensitive to RAI. There are several published trials using TKIs for redifferentiation based on the mutation present. Dabrafenib alone and in combination with other TKI’s (Vemurafenib, Trametinib) followed by RAI has shown some response in 60-70% of treated patients with RAI-R tumors. In a study with 10 RAI-R patients with BRAF V600E mutations, dabrafenib used as a radiosensitizer showed RAI uptake in 60%. Three months post Rx, 2 of 6 had a reduction in disease burden while the other 4 had stable disease. Redifferentiation Rx can be successful in slowing disease progression and could be an option in the treatment of RAI-R DTC before initiation of long term TKI Rx.

Clinical Risk Factors for Osteoporotic Fractures in Men With Non-Metastatic Prostate Cancer on Androgen Deprivation Therapy With or Without Anti-Osteoporosis Treatment

Introduction: Androgen deprivation therapy (ADT) decreases bone mineral density and increases osteoporotic fracture (OsteoFx) risk.

Hypothesis: To assess OsteoFx clinical risk factors (CRF) most predictive of future OsteoFx among men with prostate cancer on ADT.

Methods: 4370 electronic medical records were reviewed of adult men with prostate cancer on cancer therapy +/- anti-osteoporosis therapy (Anti-OsteoRx) from 2011–2019. Cancer therapy included ADT (anti-androgens, GnRH agonists & antagonists, orchiectomy) and supplemental cancer therapy (SupplRx) (prostatectomy, brachytherapy, radiation, immunotherapy, and chemotherapy). Anti-OsteoRx included bisphosphonates, denosumab, and parathyroid hormone analogs. Patients with other cancers within 5 years of initial visit, metastasis, and traumatic fractures were excluded. Retrospective analysis was done to determine baseline characteristics, type and duration of ADT, Anti-OsteoRx, SupplRx, and osteoporosis CRF.

Results: 615 men on ADT +/- SupplRx +/- Anti-OsteoRx were included in the study. 10.08% had OsteoFx irrespective of SupplRx or Anti-OsteoRx. Comparing the OsteoFx group to the non-fracture group, the following CRF were found to be statistically significant (p <0.05): age at prostate cancer diagnosis (75.10 +/- 11.80 vs 71.59 +/- 9.80 y), diabetes mellitus (DM) (33.9 vs 19%), pre-existing comorbidities affecting bone (PreCo) (41.9 vs 24.8%), steroid use (11.3 vs 4.0%), and anti-convulsant and proton-pump inhibitor (med) use (45.2 vs 26.8%).

9.89% of 374 men on ADT only without (wo) Anti-OsteoRx fractured. Statistically significant CRF for OsteoFx were age (76.86 +/- 10.55 vs 73.02 +/- 10.06 y), DM (40.5 vs 19.6%), PreCo (45.9 vs. 26.4%), and med use (48.6 vs. 25.5%).

In the following subgroups there were no statistically significant difference in CRF:•7.64% of 170 men on ADT + SupplRx wo Anti-OsteoRx •19.23% of 52 men on ADT only + Anti-OsteoRx •10.52% of 19 men on ADT + SupplRx + Anti-OsteoRx

To increase statistical power, patients on ADT +/- SupplRx were assessed:•Among 71 men on ADT +/- SupplRx + Anti-OsteoRx, there were no statistically significant differences in CRF•Among the 544 men on ADT +/- SupplRx wo Anti-OsteoRx, significant CRF for OsteoFx were age (75.16 + 11.70 vs 71.37 + 9.85 y), DM (38 vs 19.4%), PreCo (38 vs 24.1%), steroid use (12 vs 3.8%), and med use (48 vs 24.3%)

Discussion:

Men with prostate cancer requiring ADT have a higher incidence of osteoporosis defined by DXA prior to initiating ADT compared to age-matched cohorts (Hussain et al). Our study revealed ADT with CRF is associated with OsteoFx irrespective of SupplRx or Anti-OsteoRx. Limitations include inability to evaluate efficacy of Anti-OsteoRx due to insufficient power.

Conclusion: OsteoFx risk assessment utilizing CRF, FRAX, DXA with timely intervention may prevent OsteoFx in these high-risk patients.

SAT-245 A Rare Case of Clival Primary Diffuse Large B-Cell Lymphoma Presenting with Panhypopituitarism and Unmasked Diabetes Insipidus

Background: Central adrenal insufficiency (AI) is known to conceal diabetes insipidus (DI) by impairing free water clearance from the renal system and inhibiting polyuria, which is later unmasked by the initiation of glucocorticoids. The instances of masked DI in the literature are confined to case reports - the actual incidence is unclear. There have been no documented cases of masked DI secondary to a clival tumor, which remains a rare cause of hypopituitarism. Here we discuss a case of primary diffuse large B-cell lymphoma (DLBCL) of the clivus presenting with panhypopituitarism and the development of DI upon glucocorticoid initiation.

Clinical Case: A 60-year-old man with DLBCL initially presented to an outside institution with headache, diplopia, and right eye ptosis. Brain MRI showed enhancement of the clivus without obvious pituitary gland involvement. He underwent biopsy with partial resection of the tumor and pathology confirmed DLBCL. His course was complicated by persistent fevers. Extensive work-up was unrevealing and he was transferred to our institution for further management. On admission, infectious work-up was positive for C. Difficile. He later developed septic shock requiring vasopressors and broad-spectrum antibiotics. Despite prolonged antibiotics, he remained hypotensive. Due to proximity of the clivus and sella, there was concern for pituitary involvement. A random cortisol was 9.1 [3.7-19.4 ug/dL], subsequent 250ug cosyntropin stimulation test yielded 13.1 and 14.9 at 30- and 60-minutes, respectively. Given inadequate stimulation and persistent hypotension in this critically ill patient, he was then started on stress dose hydrocortisone (HC) with prompt resolution of hypotension. Further work-up of the pituitary axes was consistent with anterior hypopituitarism: ACTH 5 [6-50 pg/mL], TSH 0.336 [0.350-4.940 uIU/mL], free T4 0.5 [0.7-1.5 ng/dL], FSH 0.3/LH 0.1 [1-10 mIU/mL], IGF-1 <16 [41-279 ng/mL], prolactin <1 [3-16 ng/mL]. On day two of HC stress dosing, he developed hypernatremia and polyuria. Urine studies were consistent with DI and desmopressin was started with subsequent improvement.

Conclusion:This is the first documented case of DLBCL of the clivus leading to panhypopituitarism. For tumors in close proximity to the pituitary, there should be a low threshold for pituitary axes evaluation. In addition, masked DI from central AI remains rare and requires close attention by the Endocrinologist following initiation of glucocorticoids.