Prostate brachytherapy in New South Wales: patterns of care study and impact of caseload on treatment quality

Variation in radiotherapy patterns of care in the radical treatment of South Australian men with non-metastatic prostate cancer between 2005-2015

BACKGROUND AND PURPOSE

To investigate associations between socio-demographic characteristics and radiotherapy patterns of care in non-metastatic prostate cancer [nmPCa] in South Australia [SA] between 2005-2015 and document practice patterns over time.

MATERIALS AND METHODS

Men with nmPCa receiving primary curative radiotherapy were identified from SA Prostate Cancer Clinical Outcomes Collaborative database. Adjuvant, salvage and palliative therapies were excluded. Associations between socio-demographic factors (age, residence, socio-economic status, diagnostic period) and radiotherapy mode (external beam radiotherapy [EBRT] vs. brachytherapy [BT]) and technique (low-dose-rate vs. high-dose-rate brachytherapy) were investigated using multivariable logistic regression with separate models for clinical risk categories.

RESULTS

Of the 1874 men who underwent primary RT, 80% received EBRT and 20% BT. For low and intermediate risk disease, likelihood of receiving EBRT was higher among older men (OR_low = 3.08; 95% CI 1.82-5.22 and OR_intermediate = 3.48; 2.28-5.31 for 65-74 yrs vs. <65 yrs) and lower among regional/remote compared with metropolitan residents (OR_low = 0.34; 0.17-0.67 and OR_intermediate = 0.57; 0.34-0.94). For intermediate and high risk disease, more recent diagnosis was associated with decreased likelihood of EBRT (OR_intermediate = 0.22; 95% CI 0.15-0.33 and OR_high = 0.50; 0.29-0.88, respectively). Among men receiving BT, low-dose-rate BT use decreased over time for low (OR = 0.19; 0.04-0.89) and intermediate risk disease (OR = 0.32; 0.12-0.84). Dose escalation and intensity modulation for EBRT increased after 2010.

CONCLUSION

Over the last decade substantial changes in RT for nmPCa were observed. Older age and more remote residence may be barriers to accessing specific types of RT. Further research to understand how these factors affect access is warranted to improve service provision.

A novel model to correlate hydrogel spacer placement, perirectal space creation, and rectum dosimetry in prostate stereotactic body radiotherapy

BACKGROUND

The SpaceOAR hydrogel is employed to limit rectal radiation dose during prostate radiotherapy. We identified a novel parameter - the product of angle θ and hydrogel volume - to quantify hydrogel placement. This parameter predicted rectum dosimetry and acute rectal toxicity in prostate cancer patients treated with stereotactic body radiotherapy to 36.25 Gy in 5 fractions.

METHODS

Twenty men with low- and intermediate-risk prostate cancer underwent hydrogel placement from 2015 to 2017. Hydrogel symmetry was assessed on the CT simulation scan in 3 axial slices (midgland, 1 cm above midgland, 1 cm below midgland). Two novel parameters quantifying hydrogel placement - hydrogel volume and angle θ formed by the prostate, hydrogel, and rectum - were measured, and the normalized product of θ and hydrogel volume calculated. These were then correlated with perirectal distance, rectum maximum 1-3 cc point doses (rD_max 1-3 cc), and rectum volumes receiving 80-95% of the prescription dose (rV80-95%). Acute rectal toxicity was recorded per RTOG criteria.

RESULTS

In 50% of patients, hydrogel placement was symmetric bilaterally to within 1 cm of midline in all three CT simulation scan axial slices. Lateral hydrogel asymmetry < 2 cm in any one axial slice did not affect rectum dosimetry, but absence of hydrogel in the inferior axial slice resulted in a mean increase of 171 cGy in the rD_max 1 cc (p < 0.005). The perirectal distance measured at prostate midgland, midline (mean 9.1 ± 4.3 mm) correlated strongly with rV95 (R² 0.6, p < 0.001). The mean hydrogel volume and θ were 10.3 ± 4.5 cc and 70 ± 49°, respectively. Perirectal distance, rV95 and rD_max 1 cc correlated with hydrogel angle θ (p < 0.01), and yet more strongly with the novel metric θ*hydrogel volume (p < 0.001). With a median follow up of 14 months, no rectal toxicity >grade 2 was observed. Low grade rectal toxicity was observed in a third of men and resolved within 1 month of SBRT. Men who had these symptoms had higher rD_max 1 cc and smaller θ*hydrogel volume measurements.

CONCLUSIONS

Optimal hydrogel placement occurs at prostate midgland, midline. The novel parameter θ*hydrogel volume describes a large proportion of rectum dosimetric benefit derived from hydrogel placement, and can be used to assess the learning curve phenomenon for hydrogel placement.

Patterns of care study of brachytherapy in New South Wales: malignancies of the uterine corpus

Purpose

There are limited data at a population level on adjuvant brachytherapy (BT) practice for uterine corpus malignancies. The aims of the current study were to describe BT practice for this disease in New South Wales (NSW), to assess quality of BT, and to determine if a caseload effect on quality exists.

Material and methods

Patient, tumour, and treatment related data were collected from all nine NSW radiation oncology departments that treated patients with BT. Included patients had malignancy of the uterine corpus with treatment including BT. Brachytherapy quality was assessed using published quality benchmarks. Higher gynaecological BT caseload departments were compared with lower caseload departments.

Results

One hundred sixty-three NSW residents with gynaecological cancer were treated with BT. The four higher gynaecological BT caseload departments treated a median of 25.5 NSW residents (range 22-38), compared to median 10 (range 3-18) in the five lower caseload departments. Seventy-five patients underwent BT for uterine malignancies. Most patients had early stage endometrioid disease and were treated adjuvantly with intravaginal cylinders using high-dose-rate BT. Doses were in accordance with guideline recommendations in 83% of cases, and BT was appropriately indicated in 76% of cases. Higher caseload departments were more likely to treat with guideline doses (96% vs. 53%, p < 0.001) but there was no difference in compliance rate with treatment indications (p = 0.75).

Conclusions

Brachytherapy patients, techniques, and numbers/unit for uterine corpus malignancies were similar in NSW compared to the USA but more dispersed than in Western Europe. Doses prescribed may not be optimal in lower gynaecological BT caseload departments – the significance of this represents an area in which more research is needed.