Neuropathic Pain Features in Patients with Bone Metastases

Classification of Patients With Painful Tumors to Predict Response to Palliative Radiation Therapy

PURPOSE

This study aimed to identify factors affecting pain response to develop a patient classification system for palliative radiation therapy (RT).

METHODS AND MATERIALS

Our prospective observational study (UMIN000044984) provided data on patients who received palliative RT for painful tumors. The eligibility criteria were having a numerical rating scale (NRS) score of 2 or more before treatment and receiving palliative RT between August 2021 and September 2022. Post-RT follow-up was scheduled prospectively at 2, 4, 12, 24, 36, and 52 weeks. Pain response was assessed using the International Consensus Pain Response Endpoints criteria, with the primary outcome being the response rate within 12 weeks. Multivariable logistic regression was performed to identify factors affecting pain response and develop the classification system. Each class evaluated the differences in response rate, time to response, and progression.

RESULTS

Of the 488 registered lesions, 366 from 261 patients met the criteria. Most patients had bone metastases (75%), of whom 72% were using opioids and 22% underwent reirradiation. Conventional RT (eg, 8-Gy single fraction, 20 Gy in 5 fractions) was administered to 93% of patients. Over a median of 6.8 months of follow-up, the average NRS decreased from 6.1 to 3.4 at 12 weeks for 273 evaluable lesions, with a 60% response rate. Opioid use and reirradiation negatively affected the response rate in multivariate analysis (P < .01). Lesions were categorized into class 1 (no opioid use and no reirradiation; 89 lesions), class 2 (neither class 1 nor 3; 211 lesions), and class 3 (opioid use and reirradiation; 66 lesions), with respective response rates of 75%, 61%, and 36% (P < .001). Time to response was similar across the classes (P = .91), but the progression rates at 24 weeks differed (11%, 27%, and 63%, respectively; P < .001).

CONCLUSIONS

Opioid use and reirradiation are factors leading to significant variations in pain response rates and time to progression.

Pain Response Rates After Conventional Radiation Therapy for Bone Metastases Assessed Using International Consensus Pain Response Endpoints: A Systematic Review and Meta-Analysis of Initial Radiation Therapy and Reirradiation

Previous meta-analysis of conventional radiation therapy for painful bone metastases showed overall response (OR) rates of 72% to 75% (evaluable patients), 61% to 62% (intent-to-treat patients) for initial radiation therapy, and 68% for reirradiation (evaluable patients). However, the definition of pain response differed among the studies included. Hence, we conducted a systematic review and meta-analysis to determine the pain response rates assessed by the International Consensus Pain Response Endpoints (ICPRE) for both initial radiation therapy and reirradiation. The PubMed and Scopus databases were searched for articles published between 2002 and 2021. The inclusion criteria were (1) prospective studies or studies based on prospectively collected data and (2) studies in which pain response was assessed using ICPRE. Our primary outcomes of interest were the OR rates (sum of the complete and partial response rates) for both initial radiation therapy and reirradiation. Of the 6470 articles identified in our database search, 32 and 3 met the inclusion criteria for the analysis of initial radiation therapy and reirradiation, respectively. The OR rates of initial radiation therapy in evaluable patients (n = 4775) and intent-to-treat patients (n = 6775) were 60.4% (95% confidence interval [CI], 55.2-65.4) and 45.4% (95% CI, 38.7-52.4), respectively. The OR rates of reirradiation in evaluable patients (n = 733) and intent-to-treat patients (n = 1085) were 70.8% (95% CI, 15.7-96.9) and 62.2% (95% CI, 5.3-98.0), respectively. Subgroup analyses of initial radiation therapy including the comparison of randomized and nonrandomized studies showed no significant differences in any comparison, indicating similar response rates across different study designs. For initial radiation therapy, we determined the ICPRE-assessed response rates, which were lower than previously reported. The OR and complete response rates should be benchmarks for future randomized and nonrandomized studies. For reirradiation, the wide CIs demonstrate that the response rates based on ICPRE require further investigation.

Clinical Predictors for Analgesic Response to Radiotherapy in Patients with Painful Bone Metastases

BACKGROUND

Radiotherapy (RT) reduces pain in about 60% of patients with painful bone metastases, leaving many patients without clinical benefit. This study assesses predictors for RT effectiveness in patients with painful bone metastases.

MATERIALS AND METHODS

We included adult patients receiving RT for painful bone metastases in a multicenter, multinational longitudinal observational study. Pain response within 8 weeks was defined as ≥2-point decrease on a 0-10 pain score scale, without increase in analgesics; or a decrease in analgesics of ≥25% without increase in pain score. Potential predictors were related to patient demographics, RT administration, pain characteristics, tumor characteristics, depression and inflammation (C-reactive protein [CRP]). Multivariate logistic regression analysis with multiple imputation of missing data were applied to identify predictors of RT response.

RESULTS

Of 513 eligible patients, 460 patients (90 %) were included in the regression model. 224 patients (44%, 95% confidence interval (CI) 39%-48%) responded to RT. Better Karnofsky performance status (Odds ratio (OR) 1.39, CI 1.15-1.68), breast cancer (OR 2.54, CI 1.12-5.73), prostate cancer (OR 2.83, CI 1.27-6.33) and soft tissue expansion (OR 2.00, CI 1.23-3.25) predicted RT response. Corticosteroids were a negative predictor (OR 0.57, CI 0.37-0.88). Single and multiple fraction RT had similar response. The discriminative ability of the model was moderate; C-statistic 0.69.

CONCLUSION

This study supports previous findings that better performance status and type of cancer diagnosis predicts analgesic RT response, and new data showing that soft tissue expansion predicts RT response and that corticosteroids is a negative predictor for RT response in patients with painful bone metastases.

Potential therapeutic treatments of cancer-induced bone pain

PURPOSE OF REVIEW

The treatment of cancer-induced bone pain (CIBP) has been proven ineffective and relies heavily on opioids, the target of highly visible criticism for their negative side effects. Alternative therapeutic agents are needed and the last few years have brought promising results, detailed in this review.

RECENT FINDINGS

Cysteine/glutamate antiporter system, xc, cannabinoids, kappa opioids, and a ceramide axis have all been shown to have potential as novel therapeutic targets without the negative effects of opioids.

SUMMARY

Review of the most recent and promising studies involving CIBP, specifically within murine models. Cancer pain has been reported by 30-50% of all cancer patients and even more in late stages, however the standard of care is not effective to treat CIBP. The complicated and chronic nature of this type of pain response renders over the counter analgesics and opioids largely ineffective as well as difficult to use due to unwanted side effects. Preclinical studies have been standardized and replicated while novel treatments have been explored utilizing various alternative receptor pathways: cysteine/glutamate antiporter system, xc, cannabinoid type 1 receptor, kappa opioids, and a ceramide axis sphingosine-1-phosphate/sphingosine-1-phosphate receptor 1.

Single- Versus Multiple-Fraction Radiation Therapy for Painful Bone Metastases: A Systematic Review and Meta-analysis of Nonrandomized Studies

PURPOSE

Single-fraction radiation therapy (RT) is a convenient and cost-effective regimen for the palliation of painful bone metastases, but is still underused. Randomized controlled trials comparing single- versus multiple-fraction RT are limited by generalizability. We compared the pain response rates after single- versus multiple-fraction RT in nonrandomized studies.

METHODS AND MATERIALS

We searched PubMed and Scopus from the inception of each database through August 2018. We sought to identify nonrandomized studies in which data on pain response rates could be extracted for single- and multiple-fraction RT. Our primary outcomes of interest were the overall and complete pain response rates in evaluable patients. The analysis was performed using a random-effects model with the Mantel-Haenszel method.

RESULTS

Of the 3933 articles identified through our search, 9 met our inclusion criteria. Five of 9 included studies did not exclude patients with features of complicated bone metastases. A 1 × 8 Gy radiation schedule was frequently used in single-fraction therapy, and schedules of 5 × 4 Gy and 10 × 3 Gy were frequently used in multiple-fraction therapy. In the 9 studies, the overall response rate was 67% (884 of 1321 patients) for patients in the single-fraction arm and 70% (953 of 1360 patients) for those in the multiple-fraction arm (pooled odds ratio [OR]: 0.85; 95% confidence interval [CI], 0.66-1.08). In 5 studies, the complete response rate was 26% (195 of 753 patients) for patients in the single-fraction arm and 35% (289 of 821 patients) for those in the multiple-fraction arm (pooled OR: 0.89; 95% CI, 0.70-1.13).

CONCLUSIONS

There were no significant differences in the overall and complete response rates between single- and multiple-fraction RT. The effectiveness of single-fraction regimens was shown in nonrandomized settings, which better reflect daily practice than randomized studies. The CIs for the pooled ORs included clinically meaningful differences, and the study results are inconclusive.

Pain Response Rates After Conventional Radiation Therapy for Bone Metastases in Prospective Nonrandomized Studies: A Systematic Review

PURPOSE

This study aimed to determine the pain response rates after conventional radiation therapy (RT) for painful bone metastases in prospective nonrandomized studies, which better reflect daily practice than randomized controlled trials.

METHODS AND MATERIALS

A literature search was conducted in PubMed and Scopus for articles published between 2002 and 2018. We only included articles in which pain response after RT was assessed using the International Consensus Endpoint initially published in 2002, or the updated version from 2012. In addition, to be included in this review, the study design was required to be prospective or based on prospectively collected data. Our primary outcomes of interest were the overall and complete response rates after conventional RT for bone metastases.

RESULTS

Of the 2863 articles identified in our database search, 12 met the inclusion criteria. Six studies excluded patients with features of complicated bone metastases. Only 2 papers reported exclusion criteria regarding analgesic use. Radiation schedules that were frequently used were 1 × 8 Gy, 5 × 4 Gy, and 10 × 3 Gy. The overall response rate in evaluable patients was 55%, and 754 of the 1379 evaluable patients experienced a complete or partial response. The complete response rate was 15% (196 of 1348 evaluable patients). In the intent-to-treat patient group, the overall response rate was 29% (754 of 2559 enrolled patients), and the complete response rate 8% (196 of 2528 enrolled patients).

CONCLUSIONS

We determined the pain response rates after conventional RT for painful bone metastases in prospective nonrandomized studies. The present review may provide benchmarks for future nonrandomized studies that investigate palliative RT for bone metastases.

A neuropathic pain component as a predictor of improvement in pain interference after radiotherapy for painful tumors: A secondary analysis of a prospective observational study

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A neuropathic component was related to worse pain interference scores at baseline.

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A neuropathic component predicted a greater reduction in pain interference.

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Older patients and male patients tended to have a neuropathic component.

Background and purpose

We previously demonstrated that patients with a tumor-related neuropathic pain component were more likely to experience a pain response after radiotherapy (RT) than those without. It is unknown whether the presence of a neuropathic component also favorably influences pain interference. In a secondary analysis of our previous prospective observational study, we investigated if the presence of a neuropathic component of the index pain caused by the irradiated tumors predicts greater reduction in pain interference.

Material and methods

For patients scheduled for RT for painful tumors, Brief Pain Inventory data were collected at initiation of RT and 1, 2, and 3 months thereafter. Multivariable linear regression analyses were performed to investigate the effects of the presence of a neuropathic component on the changes in pain interference scores (i.e., follow-up minus baseline). We used 10 covariates as potential confounders.

Results

Of the 302 analyzable patients, 93 (31%) were diagnosed as having a neuropathic component of the index pain. Multivariable linear regression analyses revealed that all the point estimates of regression coefficients at 1-, 2-, and 3-month follow-up were negative values; some were statistically significant. At 2-month follow-up, patients with a neuropathic component experienced greater reductions in their pain interference scores for walking ability (p = 0.048), normal work (p = 0.021), sleep (p = 0.001), and enjoyment of life (p = 0.010) than those without it.

Conclusions

The presence of a neuropathic pain component predicted a greater reduction in pain interference after RT. Patients with neuropathic tumor-related pain should be offered the option of receiving palliative RT.

Predictors of Pain Palliation After Radiation Therapy for Painful Tumors: A Prospective Observational Study

PURPOSE

Although radiation therapy (RT) is an important part of treatment for cancer pain, prediction of the patient's pain response remains difficult. We evaluated the characteristics of patients, their tumors, and their pain to identify the predictors of pain palliation after RT for painful tumors.

METHODS

Our 3-center prospective observational study included patients scheduled for palliative or curative RT for painful tumors. Brief Pain Inventory data were collected at the start of RT and 1, 2, and 3 months thereafter. The pain response was assessed using the International Consensus Endpoint. The Mann-Whitney U-test was used to compare responders and nonresponders based on changes in the BPI scores. Predictors of the pain response were evaluated using the Fine-Gray model, in which death without a pain response was recorded as a competing risk. The independent variables were 11 a priori selected potential predictors with clinical relevance.

RESULTS

Of 302 analyzable patients, 262 (87%) had solid and 40 (13%) had hematologic tumors. The median total radiation dose was 30 Gy (range, 6-70.4 Gy). The pain response rate was 52% for 264 (87%) evaluable patients at 1-, 57% for 228 (75%) such patients at 2-, and 58% for 182 (60%) evaluable patients at 3-month follow-up. At 2-month follow-up, responders experienced a greater decrease in all 7 pain interference subscales of the Brief Pain Inventory compared to nonresponders. Multivariable analysis demonstrated that hematologic tumors (hazard ratio [HR], 1.85; 95% confidence interval [CI], 1.15-2.98), a neuropathic component of the index pain (HR, 1.50; 95% CI, 1.05-2.14), and opioid analgesic use before RT (HR, 0.65; 95% CI, 0.47-0.91) were independent significant predictors of pain response.

CONCLUSIONS

Patients with hematologic tumors, a neuropathic component of the index pain, and no treatment with opioid analgesics before RT were more likely to experience pain palliation after RT.

Targeting the S1P/S1PR1 axis mitigates cancer-induced bone pain and neuroinflammation

Metastatic bone pain is the single most common form of cancer pain and persists as a result of peripheral and central inflammatory, as well as neuropathic mechanisms. Here, we provide the first characterization of sphingolipid metabolism alterations in the spinal cord occurring during cancer-induced bone pain (CIBP). Following femoral arthrotomy and syngenic tumor implantation in mice, ceramides decreased with corresponding increases in sphingosine and the bioactive sphingolipid metabolite, sphingosine 1-phosphate (S1P). Intriguingly, de novo sphingolipid biosynthesis was increased as shown by the elevations of dihydro-ceramides and dihydro-S1P. We next identified the S1P receptor subtype 1 (S1PR1) as a novel target for therapeutic intervention. Intrathecal or systemic administration of the competitive and functional S1PR1 antagonists, TASP0277308 and FTY720/Fingolimod, respectively, attenuated cancer-induced spontaneous flinching and guarding. Inhibiting CIBP by systemic delivery of FTY720 did not result in antinociceptive tolerance over 7 days. FTY720 administration enhanced IL-10 in the lumbar ipsilateral spinal cord of CIBP animals and intrathecal injection of an IL-10 neutralizing antibody mitigated the ability of systemic FTY720 to reverse CIBP. FTY720 treatment was not associated with alterations in bone metabolism in vivo. Studies here identify a novel mechanism to inhibit bone cancer pain by blocking the actions of the bioactive metabolites S1P and dihydro-S1P in lumbar spinal cord induced by bone cancer and support potential fast-track clinical application of the FDA-approved drug, FTY720, as a therapeutic avenue for CIBP.