Exposure-toxicity relationship of cabozantinib in patients with renal cell cancer and salivary gland cancer

Cabozantinib is registered in fixed 60 mg dose. However, 46% to 62% of patients in the registration studies needed a dose reduction due to toxicity. Improved clinical efficacy has been observed in renal cell carcinoma patients (RCC) with a cabozantinib exposure greater than 750 μg/L. In our study we explored the cabozantinib exposure in patients with different tumour types. We included RCC patients from routine care and salivary gland carcinoma (SGC) patients from a phase II study with ≥1 measured C_min at steady‐state. The geometric mean (GM) C_min at the starting dose, at 40 mg and at best tolerated dose (BTD) were compared between both tumour types. Forty‐seven patients were included. All SGC patients (n = 22) started with 60 mg, while 52% of RCC patients started with 40 mg. GM C_min at the start dose was 1456 μg/L (95% CI: 1185‐1789) vs 682 μg/L (95% CI: 572‐812) (P < .001) for SGC and RCC patients, respectively. When dose‐normalised to 40 mg, SGC patients had a significantly higher cabozantinib exposure compared to RCC patients (C_min 971 μg/L [95% CI: 790‐1193] vs 669 μg/L [95% CI: 568‐788]) (P = .005). Dose reductions due to toxicity were needed in 91% and 60% of SGC and RCC patients, respectively. Median BTD was between 20 to 30 mg for SGC and 40 mg for RCC patients. GM C_min at BTD were comparable between the SGC and the RCC group, 694 μg/L (95% CI: 584‐824) vs 583 μg/L (95% CI: 496‐671) (P = .1). The observed cabozantinib exposure at BTD of approximately 600 μg/L is below the previously proposed target. Surprisingly, a comparable exposure at BTD was reached at different dosages of cabozantinib for SGC patients compared to RCC patients Further research is warranted to identify the optimal exposure and starting dose to balance efficacy and toxicity.

What's new?

Cabozantinib, a potent tyrosine kinase inhibitor that targets multiple signaling pathways, is approved for use against advanced renal cell carcinoma (RCC). Variations in cabozantinib clearance, however, warrant further investigation. Here, the authors evaluated cabozantinib exposure in RCC patients and in patients with salivary gland cancer (SGC). SGC patients were found to have significantly higher cabozantinib exposure compared to RCC patients following a 40 mg dose. However, the best‐tolerated cabozantinib exposure was equivalent (~600 μg/L) for both tumor types and was substantially below the previously proposed target. The findings offer insight on exposure, dose, and the balance between efficacy and toxicity for cabozantinib.

Abstract 1363: Exposure-toxicity analysis of cabozantinib in patients with salivary gland cancer and renal cell cancer

Background

Cabozantinib is approved for treatment of renal cell cancer (RCC) in a starting dose of 60 mg. However, in the registration studies dose reductions were needed in 46-62% of patients due to toxicity. Improved clinical efficacy of cabozantinib was observed in RCC patients with an average exposure of &gt; 750 ug/L. Data about cabozantinib pharmacokinetics in patients routinely treated with this drug is scarce, while treatment is challenging due to toxicity. Therefore, we explored the cabozantinib exposure in patients with two different tumour types in our clinic.

Methods

Clinical data and cabozantinib trough concentrations (Cmin) were collected from all patients treated with cabozantinib with at least one measured Cmin at steady state in our clinic between Jan 2018 - Aug 2020. We included salivary gland cancer (SGC) patients treated in a phase II study and RCC patients from our outpatient clinic. Geometric mean (GM) Cmin at the start dose, at 40 mg and at best tolerated dose (BTD) were compared between the two tumour types.

Results

In total 47 patients were included. All patients with SGC (n=22) started with 60 mg, while 13 of 25 patients with RCC started with 40 mg. GM Cmin level at the start dose was 1350 µg/L (95% CI 1182-1781) vs. 689 µg/L (95% CI 576-823) (P&lt;.001) for patients with SGC and RCC, respectively. When dose-normalized to 40 mg, SGC patients had a significantly higher cabozantinib exposure compared to RCC patients (GM Cmin 968 µg/L (95% CI 788-1188) vs. 676 µg/L (95% CI 571-799)(P=.007). A higher cabozantinib GM Cmin level was observed in female compared to male patients. Dose reductions due to toxicity were needed in 91% and 60% of patients with SGC and RCC, respectively. Median BTD was 25 mg for SGC patients and 40 mg for RCC patients. GM Cmin at BTD were comparable between the SGC group and the RCC group, i.e. 692 µg/L (95% CI 582-822) vs. 576 µg/L (95% CI 493-673) (P=.1), respectively. At BTD, 64% of SGC patients and 80% of RCC patients had an exposure below the proposed target of &gt;750 ug/L.

Conclusion

Unexpectedly, cabozantinib levels were significantly higher in patients with SGC compared to those with RCC at the dose of 40 mg. However, cabozantinib levels at BTD were comparable between patients with SGC and RCC. At BTD, the majority of patients did not reach the target of &gt;750 µg/L. For most patients with RCC, the cabozantinib level at BTD corresponded to a dose of 40 mg. Therefore, 40 mg instead of 60 mg as a starting dose followed by dose-adjustment based on exposure and tolerability may be preferred in patients with RCC. Although cabozantinib is not registered for SGC, an even lower starting dose of 20 mg/day may be required in these patients based on cabozantinib levels at BTD. Future studies should focus on identifying an optimal and tolerable exposure-response target value for cabozantinib and elucidate factors that contribute to the differences in exposure, in order to individualise and improve treatment.

Citation Format: Stefanie D. Krens, Wim van Boxtel, Maike J. Uijen, Frank G. Jansman, Ingrid M. Desar, Sasja F. Mulder, Carla M. van Herpen, Nielka P. van Erp. Exposure-toxicity analysis of cabozantinib in patients with salivary gland cancer and renal cell cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1363.

A phase II study on the efficacy and toxicity of cabozantinib in recurrent/metastatic salivary gland cancer patients

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A phase II study on the efficacy and toxicity of cabozantinib in recurrent/metastatic salivary gland cancer patients. Background: Because c-MET and VEGFR are often overexpressed in salivary gland cancer (SGC), this study evaluated the efficacy and safety of cabozantinib in recurrent/metastatic (R/M) SGC pts. Methods: A single center, single arm, phase II study was conducted. Immunohistochemical c-MET positive (H-score ≥10) R/M SGC pts were included in 3 cohorts: adenoid cystic carcinoma (ACC), salivary duct carcinoma (SDC), and other SGCs. Objective growth or complaints due to the disease were required before inclusion in the ACC and other SGC cohort. No prior systemic treatments were required. Pts started 60 mg cabozantinib tablets OD. Primary endpoint was the objective response rate (ORR). A Simon two-stage design was used. In case of ≥1 objective response in the first 9 pts/cohort, 8 additional pts would be included in the cohort. Results: In total 25 pts were included from Sep. 2018 until premature closure due to severe toxicity in Nov. 2019. Median age was 56 years (range 49-72), prior treatments included: primary tumor resection ( n=19), radiotherapy ≥50Gy ( n=24), systemic therapy ( n=10; adjuvant in 2 pts, palliative in 8 pts). Six pts had grade 3 ( n=4), grade 4 ( n=1), or grade 5 ( n=1) wound/fistula complications, occurring at a median of 7.2 mths on cabozantinib (range 2.1-12.8). This resulted in a severe wound complication rate of 32% in 19 pts on treatment for ≥2 mths. Remarkably, 4 out of 6 pts developed this complication in the area exposed to high-dose Rx; 2/4 had a pre-existing fistula in this area. Median interval between Rx and start of cabozantinib was 71.3 mths (range 10.6-94.7). Other grade ≥3 adverse events in >1 pt were: hypertension (5 pts), diarrhoea (2 pts) and dehydration (2 pts). Current median follow-up is 6.8 mths. The ORR was 6% (1/17 pts) in the ACC cohort, 20% (1/5 pts) in the SDC cohort, and 0% (0/3 pts) in other SGC pts; median PFS is 12.6 mths (95% CI 6.8 – 18.4 mths), 9.0 mths (insufficient events for 95% CI), and 6.9 mths (95% CI 0 – 15.2 mths), respectively. Median OS is not reached in any cohort. Conclusions: This phase II study on cabozantinib in R/M SGC pts demonstrated severe wound and fistula complications in 32% of pts on treatment for ≥2 mths, mostly (4/6 pts) within the radiotherapy field. Because of this toxicity the study was closed prematurely. Furthermore, cabozantinib showed minimal clinical activity in SGC pts. Research funding: Ipsen Pharmaceuticals Clinical trial information: NCT03729297 .

68Ga-PSMA-HBED-CC PET/CT imaging for adenoid cystic carcinoma and salivary duct carcinoma: a phase 2 imaging study

Rationale: Treatment options for recurrent and/or metastatic (R/M) adenoid cystic carcinoma (ACC) and salivary duct carcinoma (SDC), major subtypes of salivary gland cancer, are limited. Both tumors often show overexpression of prostate-specific membrane antigen (PSMA). In prostate cancer, PSMA-ligands labeled with ⁶⁸Ga or ¹⁷⁷Lu are used for imaging and therapy, respectively. Primary aim of this study in R/M ACC and SDC patients was to systematically investigate ⁶⁸Ga-PSMA-uptake by PET/CT imaging to determine if PSMA radionuclide therapy could be a treatment option.

Methods: In a prospective phase II study, PET/CT imaging was performed 1 h post injection of ⁶⁸Ga-PSMA-HBED-CC in 15 ACC patients and 10 SDC patients. Maximum standardized uptake values (SUV) were determined in tumor lesions. Immunohistochemical PSMA expression was scored in primary tumors and metastatic tissue. Standard imaging (MRI or CT) was performed for comparison.

Results: In ACC patients, SUV_max ranged from 1.1 to 30.2 with a tumor/liver-ratio >1 in 13 out of 14 evaluable patients (93%). In SDC patients, SUV_max ranged from 0.3 to 25.9 with a tumor/liver-ratio >1 in 4 out of 10 patients (40%). We found a large intra-patient inter-metastatic variation in uptake of ⁶⁸Ga-PSMA, and immunohistochemistry did not predict ligand uptake in ACC and SDC. Finally, PSMA-PET detected additional bone metastases compared to CT in 2 ACC patients with unexplained pain.

Conclusion: In 93% of ACC patients and 40% of SDC patients we detected relevant PSMA-ligand uptake, which warrants to study PSMA radionuclide therapy in these patients. Additionally, our data provide arguments for patient selection and treatment timing. Finally, PSMA-PET imaging has added diagnostic value compared to CT in selected patients.

Prediction of clinical benefit from androgen deprivation therapy in salivary duct carcinoma patients

Androgen deprivation therapy (ADT) is first‐line palliative treatment in androgen receptor‐positive (AR+) salivary duct carcinoma (SDC), and response rates are 17.6–50.0%. We investigated potential primary ADT resistance mechanisms for their predictive value of clinical benefit from ADT in a cohort of recurrent/metastatic SDC patients receiving palliative ADT (n = 30). We examined mRNA expression of androgen receptor (AR), AR splice variant‐7, intratumoral androgen synthesis enzyme‐encoding genes AKR1C3, CYP17A1, SRD5A1 and SRD5A2, AR protein expression, ERBB2 (HER2) gene amplification and DNA mutations in driver genes. Furthermore, functional AR pathway activity was determined using a previously reported Bayesian model which infers pathway activity from AR target gene expression levels. SRD5A1 expression levels and AR pathway activity scores were significantly higher in patients with clinical benefit from ADT compared to those without benefit. Survival analysis showed a trend toward a longer median progression‐free survival for patients with high SRD5A1 expression levels and high AR pathway activity scores. The AR pathway activity analysis, and not SRD5A1 expression, also showed a trend toward better disease‐free survival in an independent cohort of locally advanced SDC patients receiving adjuvant ADT (n = 14) after surgical tumor resection, and in most cases a neck dissection (13/14 patients) and postoperative radiotherapy (13/14 patients). In conclusion, we are the first to describe that AR pathway activity may predict clinical benefit from ADT in SDC patients, but validation in a prospective study is needed.

What's new?

Androgen deprivation therapy (ADT) is a leading treatment strategy in the palliative care of patients with androgen receptor (AR)‐positive salivary duct carcinoma (SDC). However, while as many as half of patients may respond to ADT, resistance frequently emerges, undermining its use. In this investigation of primary ADT resistance mechanisms, expression of the androgen synthesis enzyme‐encoding gene SRD5A1 and functional activity of the AR pathway were found to predict clinical benefit from ADT in SDC patients. High AR pathway activity scores were further linked to improved disease‐free survival in SDC patients with locally advanced disease who received adjuvant ADT.

Asymmetries in Gait and Balance Control After Ankle Arthrodesis

Previous gait analysis studies of patients with an ankle arthrodesis have reported increased motion in the adjacent joints. However, of similar importance are the forces that act on the ipsi- and contralateral joints and the effect of ankle arthrodesis with regard to balance control. The purpose of the present study was to determine the joint moments and the amount of asymmetrical loading of the ankle and joints adjacent to the ankle in patients after successful ankle arthrodesis. Therefore, 8 patients with a painless ankle fusion were included and assessed using 4 functional tests: preferred and fast speed walking, a sit-to-stand test, and a balance test. The ground reaction force and ankle joint moment were smaller in the fused ankle. During the balance on foam test, the velocity of the center of pressure was significantly larger on the contralateral extremity. In conclusion, ankle arthrodesis leads to small asymmetries in joint moments during gait, indicating greater loading of the contralateral ankle. In addition, the unaffected leg compensates for the operated leg in balance control. Because of the small alterations, overuse of the contralateral ankle is not expected after ankle arthrodesis.

A clinicopathological study and prognostic factor analysis of 177 salivary duct carcinoma patients from The Netherlands

Salivary duct carcinoma (SDC) is a subtype of salivary gland cancer with a dismal prognosis and a need for better prognostication and novel treatments. The aim of this national cohort study was to investigate clinical outcome, prognostic factors, androgen receptor (AR) and human epidermal growth factor receptor 2 (HER2) expression. SDC patients diagnosed between 1990 and 2014 were identified by the Nationwide Network and Registry of Histo‐ and Cytopathology in the Netherlands (PALGA). Subsequently, medical records were evaluated and pathological diagnoses reviewed. Data were analyzed for overall survival (OS), disease‐free survival (DFS), distant metastasis‐free survival (DMFS) and prognostic factors. AR was evaluated by immunohistochemistry (IHC), HER2 by IHC and fluorescent in‐situ hybridization. A total of 177 patients were included. The median age was 65 years, 75% were male. At diagnosis, 68% presented with lymph node metastases and 6% with distant metastases. Median OS, DFS and DMFS were 51, 23 and 26 months, respectively. In patients presenting without distant metastases, the absolute number of positive lymph nodes was associated with poor OS and DMFS in a multivariable analysis. AR and HER2 were positive in 161/168 (96%) and 44/153 (29%) tumors, respectively, and were not prognostic factors. SDC has a dismal prognosis with primary lymph node involvement in the majority of patients. The absolute number of lymph node metastases was found to be the only prognostic factor for DMFS and OS. AR expression and—to a lesser extent—HER2 expression hold promise for systemic treatment in the metastatic and eventually adjuvant setting.

What's new?

Salivary duct carcinoma (SDC) is a rare and often fatal malignancy. Little is known about associations between its pathological features and clinical outcome. In this study, clinicopathological factors were analyzed for 177 patients diagnosed with SDC in The Netherlands between 1990 and 2014. The data show that median overall survival (OS) and distant metastasis‐free survival (DMFS) were 51 and 26 months, respectively. At diagnosis, 68% of patients presented with lymph node metastases. Lymph node positivity was associated with poor OS and poor DMFS. The absolute number of metastatic lymph nodes was the only significant prognostic factor for survival in a multivariate analysis. Androgen receptor and human epidermal growth factor 2 (HER2) were positive in 96% and 29%, respectively and were not a prognostic factor.

Androgen deprivation therapy for androgen receptor-positive advanced salivary duct carcinoma: A nationwide case series of 35 patients in The Netherlands

Background

Salivary duct carcinoma, an aggressive subtype of salivary gland cancer, is mostly androgen receptor‐positive. Only limited data are available on androgen deprivation therapy (ADT).

Methods

Patients with advanced androgen receptor‐positive salivary duct carcinoma treated with first‐line ADT were retrospectively evaluated for clinical benefit (ie, partial response [PR] and stable disease, progression‐free survival [PFS] and overall survival [OS]). The OS was compared with patients with advanced salivary duct carcinoma who received best supportive care.

Results

Thirty‐four of 35 patients who were ADT‐treated were evaluable: 6 patients had a PR (18%) and 11 had stable disease (32%) leading to a clinical benefit ratio of 50%. The median PFS for the ADT‐treated patients was 4 months and the median duration of clinical benefit was 11 months. The median OS was 17 months versus 5 months in 43 patients receiving best supportive care (P = .02).

Conclusion

We recommend ADT in advanced androgen receptor‐positive salivary duct carcinoma given its response and clinical benefit. © 2017 Wiley Periodicals, Inc. Head Neck, 2017