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Liu et al. (2010): Influence of vitamin C on salivary absorbed dose of 131I in thyroid cancer patients: a prospective, randomized, single-blind, controlled trial

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Title Influence of vitamin C on salivary absorbed dose of 131I in thyroid cancer patients: a prospective, randomized, single-blind, controlled trial
Topic Vitamin C
Author Liu, B, Kuang, A, Huang, R, Zhao, Z, Zeng, Y, Wang, J, Tian, R
Year 2010
Journal Journal of nuclear medicine
DOI http://dx.doi.org/10.2967/jnumed.109.071449

Study Note

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Brief summary

In this study, four different arms of thyroid cancer patients were examined, each beginning at different times to suck dissolved vitamin C in addition to radioiodine therapy to stimulate saliva flow (1, 5, 13, or 25 hours after radioiodine therapy). The aim of the vitamin C administration was to accelerate the excretion of radioiodine from the salivary glands by stimulating saliva flow, thereby protecting the salivary glands. The authors found no significant differences between the four arms regarding the radioactive exposure of the salivary glands. A drawback of this study is the absence of a control group that received no vitamin C at all. Therefore, this study only indicates that there are no differences regarding the timing of vitamin C administration.

Study Design

Prospective / Retrospective Prospective: forward-looking, examples include clinical trials, cohort studies, and long-term observational studies;</br>Retrospective: backward-looking, relying on existing data, examples include case-control studies and retrospective cohort studies Prospective
Monocentric / Multicentric Monocentric: conducted in one center/ hospital; </br>Multicentric: conducted in multiple centers/ hospitals Monocentric
Blinding No: Open, all parties are aware of group assignments;</br>Single: one party is unaware of group assignments (generally participants);</br>Double: two parties are unaware of group assignments (generally the participants and the researchers); </br>Triple: concealing group assignment from additional parties Single
Is randomized Yes
Cross-over Participants alternate between different treatment groups or conditions over a specified period, allowing each participant to serve as their own control No
Number of arms 4

Study characteristics

Inclusion criteria 18 y old, case of recently diagnosed differentiated papillary or follicular thyroid cancer, undergone total thyroidectomy, referred to the Department of Nuclear Medicine, West China Hospital, for ablation of remnant thyroid tissue, stage pT1–T3, N0–N1, M0. For women of childbearing potential: a negative result on serum human chorionic gonadotropin pregnancy testing required
Exclusion criteria Presence of distant metastases; a previous history of salivary gland disorders, collagen tissue disease, diabetes, previous 131I therapy, or external radiation to the head or neck; or difficulty drinking a large amount of water.
N randomized 80
Analysis PP: Per Protocol analysis, i.e. only participants included who adhered to the study protocol.</br>ITT: Intention-to-treat analysis, i.e. all randomized participants included regardless of any drop-outs or changes in assignment.</br>mITT: modified Intention-to-treat analysis can refer to analyses in which participants with missing outcome data are excluded or it can refer to analyses in which only participants who received at least one treatment dose are included. In this case, participants dropped out of the study prematurely for reasons unrelated to the treatment. PP Analysis
Specifications on analyses NI
Countries of data collection China
LoE Level of evidence 2b Oxford 2009
Outcome timeline Data collection times A: 1 hour after ingestion of 131I

B: 5 hours after ingestion of 131I C: 13 hours after ingestion of 131I D: 25 hours after ingestion of 131I

Characteristics of participants

Setting Refers to cancer therapy setting.</br>- Curative therapy: aims to completely eradicate a disease and achieve a full recovery; </br>- Neo-adjuvant therapy: form of curative therapy, given before the primary treatment for cancer (usually surgery); </br>- Adjuvant therapy: form of curative therapy, given after the primary treatment for cancer (usually surgery); </br>- Palliative therapy: focuses on providing relief from symptoms and improving the quality of life for patients, without necessarily targeting the underlying disease; </br>- Active surveillance: involves close monitoring of disease progression without any intervention (typically used for prostate cancer);</br>- No therapy setting: Patients who completed therapy/are currently not in cancer treatment, cancer survivors. NI
Types of cancer "Other Cancers" means that only a subpopulation was specified, but further unspecified cancer types were included Head and Neck Cancers - Thyroid Cancer
Cancer stages Early Stage: generally refers to cancer that is localized to the area where it started, mostly stages I and II;</br>Advanced Stage: cancer that has spread beyond its original site, mostly stages III and IV, with stage IV indicating distant metastasis Early Stage
Specifications on cancer stages pT1–T3, N0–N1, M0
Comorbidities NI
Current cancer therapies Radioiodine treatment
Specifications on cancer therapies Radioiodine therapy (131I)
Previous cancer therapies Surgery
Gender Mixed
Gender specifications Number (n, M/F):

Arm A: 1/16 Arm B: 3/15 Arm C: 7/12 Arm D: 2/15

Age groups Adults (18+)
Age groups specification Mean (SD)

Arm A: 44 (14) Arm B: 42 (14) Arm C: 43 (13) Arm D: 39 (12)

Arms

Arm type Active control: group receives active treatment; </br>Passive control: for example treatment as usual, waiting control, no treatment Intervention
Number of participants (arm) N randomized 20
Drop-out Number of participants who left the study for any reason or did not provide information on every data collection date 2
Drop-out reasons Did not complete salivary dosimetry measurements
Intervention Sucking vitamin C at 1 hour after ingestion of 131I
Dosage and regime 100 mg every 4 h in the daytime over 6 d
One-time application No
Duration in days For long-term interventions, the number of days is an estimation.</br>A value of -999 indicates that the exact duration cannot be extracted from the study due to ambiguous or incomplete information. See Outcome timeline or Dosage and regime for further information. 6
Side effects / Interactions NI
Arm type Active control: group receives active treatment; </br>Passive control: for example treatment as usual, waiting control, no treatment Intervention
Number of participants (arm) N randomized 20
Drop-out Number of participants who left the study for any reason or did not provide information on every data collection date 2
Drop-out reasons Showed distant metastases on posttherapy scans
Intervention Sucking vitamin C at 5 hours after ingestion of 131I
Dosage and regime 100 mg every 4 h in the daytime over 6 d
One-time application No
Duration in days For long-term interventions, the number of days is an estimation.</br>A value of -999 indicates that the exact duration cannot be extracted from the study due to ambiguous or incomplete information. See Outcome timeline or Dosage and regime for further information. 6
Side effects / Interactions NI
Arm type Active control: group receives active treatment; </br>Passive control: for example treatment as usual, waiting control, no treatment Intervention
Number of participants (arm) N randomized 20
Drop-out Number of participants who left the study for any reason or did not provide information on every data collection date 1
Drop-out reasons Showed distant metastases on posttherapy scans
Intervention Sucking vitamin C at 13 hours after ingestion of 131I
Dosage and regime 100 mg every 4 h in the daytime over 6 d
One-time application No
Duration in days For long-term interventions, the number of days is an estimation.</br>A value of -999 indicates that the exact duration cannot be extracted from the study due to ambiguous or incomplete information. See Outcome timeline or Dosage and regime for further information. 6
Side effects / Interactions NI
Arm type Active control: group receives active treatment; </br>Passive control: for example treatment as usual, waiting control, no treatment Intervention
Number of participants (arm) N randomized 20
Drop-out Number of participants who left the study for any reason or did not provide information on every data collection date 3
Drop-out reasons Did not complete salivary dosimetry measurements
Intervention Sucking vitamin C at 25 hours after ingestion of 131I
Dosage and regime 100 mg every 4 h in the daytime over 6 d
One-time application No
Duration in days For long-term interventions, the number of days is an estimation.</br>A value of -999 indicates that the exact duration cannot be extracted from the study due to ambiguous or incomplete information. See Outcome timeline or Dosage and regime for further information. 6
Side effects / Interactions NI

Outcomes

Salivary gland function

Outcome type As specificed by the authors Primary
Outcome specification Salivary activity
Type of measurement Scintigraphy
Results during intervention - Results during intervention means that the time of data collection is during or shortly after the period of the intervention (e.g. on the last day or a few days after). The results therefore still relate to the direct effects of the intervention.</br>- Results after intervention means there is a longer break between the time of data collection and the end of the intervention, e.g. more than a week. The results relate more to long-term effects.</br>- If a categorization in Results during vs. after intervention is not possible (e.g. survival data), the results are summarized under Results after intervention under the headline "Overall". No data available
Results after intervention - Results during intervention means that the time of data collection is during or shortly after the period of the intervention (e.g. on the last day or a few days after). The results therefore still relate to the direct effects of the intervention.</br>- Results after intervention means there is a longer break between the time of data collection and the end of the intervention, e.g. more than a week. The results relate more to long-term effects.</br>- If a categorization in Results during vs. after intervention is not possible (e.g. survival data), the results are summarized under Results after intervention under the headline "Overall". No data available
Risk of Bias Assessment: Cochrane RoB tool 2.0
Bias arising from the randomization process ?
Bias due to deviation from intended intervention (assignment to intervention) ?
Bias due to deviation from intended intervention (adhering to intervention) NA
Bias due to missing outcome data ?
Bias in measurement of the outcome ?
Bias in selection of the reported result ?
Other sources of bias ?
Overall RoB judgment ?

Salivary gland function

Outcome type As specificed by the authors Primary
Outcome specification Salivary absorbed sose, calculated from the 131I activity administered, saliva retention time and salivary gland mass (determined by CT)
Type of measurement CT (Computed Tomography)
Results during intervention - Results during intervention means that the time of data collection is during or shortly after the period of the intervention (e.g. on the last day or a few days after). The results therefore still relate to the direct effects of the intervention.</br>- Results after intervention means there is a longer break between the time of data collection and the end of the intervention, e.g. more than a week. The results relate more to long-term effects.</br>- If a categorization in Results during vs. after intervention is not possible (e.g. survival data), the results are summarized under Results after intervention under the headline "Overall". Single parotid gland: no differences between arms (p=0.37)

Single submandibular gland: no differences between arms (p=0.28)

Results after intervention - Results during intervention means that the time of data collection is during or shortly after the period of the intervention (e.g. on the last day or a few days after). The results therefore still relate to the direct effects of the intervention.</br>- Results after intervention means there is a longer break between the time of data collection and the end of the intervention, e.g. more than a week. The results relate more to long-term effects.</br>- If a categorization in Results during vs. after intervention is not possible (e.g. survival data), the results are summarized under Results after intervention under the headline "Overall". NA
Risk of Bias Assessment: Cochrane RoB tool 2.0
Bias arising from the randomization process ?
Bias due to deviation from intended intervention (assignment to intervention) ?
Bias due to deviation from intended intervention (adhering to intervention) NA
Bias due to missing outcome data ?
Bias in measurement of the outcome ?
Bias in selection of the reported result ?
Other sources of bias ?
Overall RoB judgment ?

Salivary gland function

Outcome type As specificed by the authors Primary
Outcome specification Salivary cumulated activities in first 24h after 131I ingestion divided by total cumulated activities
Type of measurement Scintigraphy
Results during intervention - Results during intervention means that the time of data collection is during or shortly after the period of the intervention (e.g. on the last day or a few days after). The results therefore still relate to the direct effects of the intervention.</br>- Results after intervention means there is a longer break between the time of data collection and the end of the intervention, e.g. more than a week. The results relate more to long-term effects.</br>- If a categorization in Results during vs. after intervention is not possible (e.g. survival data), the results are summarized under Results after intervention under the headline "Overall". Parotid gland: no differences between arms (p=0.21)

Submandibular gland: no differences between arms (p=0.16)

Results after intervention - Results during intervention means that the time of data collection is during or shortly after the period of the intervention (e.g. on the last day or a few days after). The results therefore still relate to the direct effects of the intervention.</br>- Results after intervention means there is a longer break between the time of data collection and the end of the intervention, e.g. more than a week. The results relate more to long-term effects.</br>- If a categorization in Results during vs. after intervention is not possible (e.g. survival data), the results are summarized under Results after intervention under the headline "Overall". NA
Risk of Bias Assessment: Cochrane RoB tool 2.0
Bias arising from the randomization process ?
Bias due to deviation from intended intervention (assignment to intervention) ?
Bias due to deviation from intended intervention (adhering to intervention) NA
Bias due to missing outcome data ?
Bias in measurement of the outcome ?
Bias in selection of the reported result ?
Other sources of bias ?
Overall RoB judgment ?

Salivary gland function

Outcome type As specificed by the authors Primary
Outcome specification Salivary absorbed dose during the first 24 h after 131I ingestion, calculated from the 131I activity administered, saliva retention time and salivary gland mass (determined by CT)
Type of measurement CT (Computed Tomography)
Results during intervention - Results during intervention means that the time of data collection is during or shortly after the period of the intervention (e.g. on the last day or a few days after). The results therefore still relate to the direct effects of the intervention.</br>- Results after intervention means there is a longer break between the time of data collection and the end of the intervention, e.g. more than a week. The results relate more to long-term effects.</br>- If a categorization in Results during vs. after intervention is not possible (e.g. survival data), the results are summarized under Results after intervention under the headline "Overall". Parotid gland: no differences between arms (p=0.32)

Submandibular gland: no differences between arms (p=0.24)

Results after intervention - Results during intervention means that the time of data collection is during or shortly after the period of the intervention (e.g. on the last day or a few days after). The results therefore still relate to the direct effects of the intervention.</br>- Results after intervention means there is a longer break between the time of data collection and the end of the intervention, e.g. more than a week. The results relate more to long-term effects.</br>- If a categorization in Results during vs. after intervention is not possible (e.g. survival data), the results are summarized under Results after intervention under the headline "Overall". NA
Risk of Bias Assessment: Cochrane RoB tool 2.0
Bias arising from the randomization process ?
Bias due to deviation from intended intervention (assignment to intervention) ?
Bias due to deviation from intended intervention (adhering to intervention) NA
Bias due to missing outcome data ?
Bias in measurement of the outcome ?
Bias in selection of the reported result ?
Other sources of bias ?
Overall RoB judgment ?

Funding and Conflicts of Interest

Funding This work was supported by the National Natural Science Fund of China (grants 30670585 and 30870724).
Conflicts of Interest NI

Further points for assessing the study

Sample

Power analysis performed ?
- Sample size corresponds to power analysis
- Reasons for insufficient sample size based on power analysis
If no power analysis performed: at least moderate sample size (n >= 30 per arm) ?
Ethnicity mentioned ?

Alternative Explanation

Other explanations for an effect besides the investigated intervention
- Possibility of attention effects ?
- Possibility of placebo effects ?
- Other reasons ?

Statistics

Correct use of parametric and non-parametric tests Testing for normal distribution only necessary if parametric tests are used, NI: use of parametric tests without report of normal distribution testing
Correction for multiple testing ?
Measurement of compliance ?
Consistent reporting in numbers (figures, flowchart, abstract, results) ?
Comprehensive and coherent reporting ?
Cross-over
- Sufficient washout period ?
- Tested for carry-over effects ?
- Tested for sequence effects ?

Interpretation of results

Effect sizes reported (clinical vs. statistical significance) ?
Side effects systematically recorded ?
Side effects considered in result interpretation ?
Ethics votum ?


Additional Notes

PRO Low dropout, evenly distributed per arm

CONTRA Very small sample size per arm No comparison sample without vitamin C

Only a few baseline characteristics investigated (no information to cancer stage); arm differences possible.

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