Short abstract
Adding to the limited literature on the subject, this letter to the editor focuses on the trend in the use of stereotactic radiation therapy for metastatic renal cell carcinoma.
Paciotti et al. recently reported an increasing trend in the use of stereotactic radiation therapy (SRT) for metastatic renal cell carcinoma (mRCC) using data from the U.S. National Cancer Database (NCDB) [1]. We have found similar—yet in some ways different—trends in Australia that will expand the evidence base in this rapidly evolving field.
We used data from the population‐based Victorian Radiotherapy Minimum Dataset in Australia to identify radiation therapy (RT) courses delivered between 2012 and 2017 in patients with mRCC and limited our analyses to RT to bone and brain metastases, as these are the most common metastatic sites of mRCC [1]. The RT techniques were classified as SRT versus non‐SRT for bone metastases based on reporting by individual institutions, whereas the definition for stereotactic radiosurgery (SRS) for brain metastases was defined according to an earlier Australian study [2].
There were 425 patients who received 733 RT courses for bone metastases in our cohort—of these, 3% of RT courses were SRT (Table‐1). The Cochran‐Armitage test for trend showed marked increase in SRT use from 0% in 2012 to 10% in 2017 (p < .001), consistent with that seen in the U.S. [1]. In multivariable logistic regressions (employing robust standard error (SE) by clustering patients who had multiple courses of RT), factors independently associated with increased likelihood of SRT use for bone metastases were as follows: more recent year of RT (odds ratio [OR], 2.49; 95% confidence interval [CI], 1.53–4.06; p < .001), younger age at time of RT (OR, 0.94; 95% CI, 0.90–0.99; p = .02), female (OR, 4.9; 95% CI, 1.16–21.0; p = .03), and treatment in private institutions (OR, 7.61; 95% CI, 2.18–26.5; p = .001). One hundred thirty‐two patients received 184 RT courses for brain metastases—of these, 53% of RT courses were SRS (Table 1). There was an 8% absolute increase in SRS use over time, from 55% in 2012 to 63% in 2017 (p = .06). There was no statistically significant association between the different factors and SRS use for brain metastases in multivariable analyses. No SRT or SRS was delivered in regional institutions.
Table 1.
Factors associated with stereotactic radiation therapy/stereotactic radiosurgery use for bone and brain metastases in metastatic renal cell carcinoma
| Characteristics | Bone metastases | Brain metastases | ||||
|---|---|---|---|---|---|---|
| Non‐SRT, n (%) | SRT, n (%) | p value a | Non‐SRS, n (%) | SRS, n (%) | p value a | |
| Number of RT courses (%) | 712 (97) | 21 (2.9) | 86 (47) | 98 (53) | ||
| Year of RT | ||||||
| 2012 | 102 (100) | 0 (0) | <.001 b | 5 (45) | 6 (55) | .06 b |
| 2013 | 124 (100) | 0 (0) | 15 (75) | 5 (25) | ||
| 2014 | 119 (97) | 4 (3.3) | 9 (43) | 12 (57) | ||
| 2015 | 144 (98) | 3 (2.0) | 18 (46) | 21 (54) | ||
| 2016 | 124 (98) | 3 (2.4) | 21 (47) | 24 (53) | ||
| 2017 | 99 (90) | 11 (10) | 18 (38) | 30 (63) | ||
| Age at RT, years | ||||||
| Mean ± SD | 67.3 ± 11.3 | 62.2 ± 9.0 | 67.6 ± 10.9 | 63.3 ± 11.3 | ||
| <60 | 183 (96) | 7 (4) | .09 | 19 (35) | 35 (65) | .07 |
| 60–69 | 224 (96) | 10 (4) | 30 (47) | 34 (53) | ||
| 70–79 | 305 (99) | 4 (1) | 37 (56) | 29 (44) | ||
| Sex | ||||||
| Male | 524 (98) | 13 (2) | .2 | 60 (46) | 74 (54) | .68 |
| Female | 188 (96) | 8 (4) | 26 (49) | 27 (51) | ||
| Socioeconomic status | ||||||
| First quintile (lowest) | 138 (99) | 1 (0.7) | .04 | 10 (56) | 8 (44) | .09 |
| Second quintile | 119 (97) | 4 (3.3) | 11 (50) | 11 (50) | ||
| Third quintile | 164 (97) | 5 (3.0) | 23 (52) | 21 (48) | ||
| Fourth quintile | 133 (99) | 1 (0.8) | 20 (61) | 13 (39) | ||
| Fifth quintile (highest) | 158 (94) | 10 (6.0) | 22 (34) | 43 (66) | ||
| Remoteness of residence | ||||||
| Major cities | 472 (96) | 19 (4) | .02 | 56 (42) | 77 (58) | .04 |
| Regional/remote | 240 (99) | 2 (1) | 30 (59) | 21 (41) | ||
| Treatment institution type | ||||||
| Public | 480 (99) | 5 (1) | <.001 | 51 (40) | 76 (60) | .008 |
| Private | 232 (94) | 16 (6) | 35 (61) | 22 (39) | ||
| Treatment institution location | ||||||
| Metropolitan | 531 (96) | 21 (3.8) | .008 | 62 (39) | 98 (61) | <.001 |
| Regional | 181 (100) | 0 (0) | 24 (100) | 0 (0) | ||
p values based on Pearson's chi‐squared test.
p value based on Cochran‐Armitage test for trend.
Abbreviations: RT, radiation therapy; SRT, stereotactic radiation therapy; SRS, stereotactic radiosurgery.
These data, while smaller in number compared with the U.S. NCDB, are to the best of our knowledge the only Australian population‐based series to date, adding to the very limited real‐life literature in SRT/SRS use for mRCC [1]. Although SRT for bone metastases is only gaining traction in more recent years in our cohort, SRS use for brain metastases is already relatively common for mRCC, and in fact its use is more common compared with brain metastases from other primary cancers [2]. In comparison with Paciotti et al., we did not find patients’ socioeconomic and remoteness of residence to be associated with SRT/SRS use in multivariate analyses, suggesting that patients in our cohort most likely had access to metropolitan centres in Victoria providing SRT/SRS services.
With technological advancement and increasing experience with SRT/SRS, in conjunction with increasing efficacy of targeted systemic therapy and immunotherapies for mRCC [3], we anticipate that SRT/SRS will be an integral modality in treatment for mRCC in combination with systemic therapies [4]. However, it is important to ensure equal and easy access to SRT/SRS services for all patients with cancer who will benefit from it.
Disclosures
The authors indicated no financial relationships.
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Editor's Note: See the Letter article, “Temporal Trends and Predictors in the Use of Stereotactic Body Radiotherapy for Treatment of Metastatic Renal Cell Carcinoma in the U.S” by Marco Paciotti, Andrew L. Schmidt, Praful Ravi, et al., on page e905 on 26:5 issue.
References
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