Upright positioning of patients for prostate cancer radiation therapy may have benefits

Delivering radiation therapy to patients with prostate cancer in the upright position may hold benefits over treatment delivered in the supine position due to anatomical changes in the male pelvis, according to a study conducted by investigators at Leo Cancer Care, in Surrey, the United Kingdom.^1,2

Each participant underwent an MRI scan in the supine position and in the upright position with a full and voided bladder

The findings were published in the Journal of Applied Clinical Medical Physics.

"The study revealed that the anatomical changes in the male pelvis could potentially favor the upright position for prostate treatments,” said Leo Cancer Care Chief Scientific Officer Niek Schreuder in a news release on the findings.² “The increased downward pressure from the abdominal contents on the bladder and prostate in the upright position appears to have a stabilization effect on the prostate [because] the changes in bladder fill did not [affect] the prostate position and orientation in the same manner as reported in the literature for the supine position. This holds great promise for upright prostate treatments removing the burden of reproducing the bladder volume at the time of the CT scan.”

In total, 15 patients between 55 and 75 years of age were included in the study. Each participant underwent an MRI scan in the supine position and in the upright position with a full and voided bladder in order to observe anatomical changes in the pelvis. Statistical analyses were done with both a 2-sided standard paired t-test (PTT) as well as with a Wilcoxon Signed Rank Sum Test with a Gaussian Approximation (WRGA).

The investigators found that the distance between the tip of the S1 vertebra and the bladder neck (or top of the prostate) was significantly larger when imaging was done in the upright position compared with the supine position (P = .014, PTT; P = .011, WRGA), indicating a shift of the prostate inferiorly.

The anterior to posterior lengths of the bladder were also significantly longer in the upright position compared with in the supine position (P < .001, PTT and WRGA). Conversely, imaging in the upright position resulted in a smaller distance between the posterior edge of the bladder and the sacrum compared with imaging in the supine position (P = .0032.6 × 10−3, PT; P < .001 = 8 × 10−4, WRGA).

Further, in the upright position, the penile bulb for a full bladder was found to be further away from the apex of the prostate (P = .02, PTT; P = .02, WRGA). The authors note that the separation observed with the upright approach could result in a small reduction in the average dose to the penile bulb.

Prostate shape and position were not found to be significantly different in the upright position when the bladder was full compared with when it was empty (P > .05). However, the seminal vesicles appeared to be pushed downwards when the bladder was full due to the posterior positioning of the bladder with the upright approach. According to the investigators, this may mean that “the upright orientation will allow for a much larger volume of the seminal vesicles to be treated using the same field size or that a smaller field can be used to treat the same volume of seminal vesicles.”

The authors concluded, “The primary conclusion therefore is that there was nothing observed in this study of the male pelvic anatomy that would prevent prostate treatments in the upright orientation.The preliminary data suggests some advantages in treating in upright position, but more research including dosimetric comparisons when CT data of the pelvic region becomes available is recommended.”

References

1. Schreuder A, Hsi WC, Greenhalgh J, et al. Anatomical changes in the male pelvis between the supine and upright positions—A feasibility study for prostate treatments in the upright position. J Appl Clin Med Phys. Published online July 24, 2023. Accessed August 8, 2023. doi:10.1002/acm2.14099

2. Study conducted by Leo Cancer Care indicates treating prostate patients with radiation therapy in the upright position shows “promise.” News release. Leo Cancer Care. August 3, 2023. Accessed August 8, 2023. https://www.prnewswire.com/news-releases/study-conducted-by-leo-cancer-care-indicates-treating-prostate-patients-with-radiation-therapy-in-the-upright-position-shows-promise-301892702.html