Degree of Rectal Distension Seen on Prostate Radiotherapy Planning CT Scan Is Not a Negative Prognostic Factor in the Modern Era of Image-Guided Radiotherapy

Abstract

Background: Studies have shown that rectal distension has a significant impact on treatment failure in patients receiving radical radiotherapy for prostate cancer. A distended rectum contributes to excessive organ movement during treatment, resulting in significant underdosing of the target volume and higher treatment failure rates. The increasing use of highly conformal, precise radiotherapy techniques places greater importance on reducing this risk. We tested whether imaging during radiotherapy helps minimise the negative impact that rectal distension has on long-term tumour control. Findings: The rectal diameter (anterior/posterior and lateral) was prospectively measured at radiotherapy planning in 172 consecutive patients undergoing radical radiotherapy with three-dimensional conformal radiotherapy. Daily, and then weekly, imaging during radiotherapy ensured that prostate movement remained within predefined tolerances. Patients were followed up for a median of 72 months with regular prostate-specific antigen (PSA) measurements to ascertain biochemical PSA relapse and survival information. Conclusions: In this cohort of predominately high-risk localised prostate cancer, rectal distension had no significant impact on PSA relapse. We suggest that regular imaging during radiotherapy negates the risk caused by rectal distension on local treatment failure.

Rectal volume variations and estimated rectal dose during 8 weeks of image-guided radical 3D conformal external beam radiotherapy for prostate cancer

“…This study demonstrated a reduced 5-year FFBF in patients with a larger rectal distention on the planning CT-scan compared to those with limited rectal distention (75% vs 89%). Other authors claim that the adverse effects of rectal distention on local control can be compensated by the use of modern IGRT [12] , [28] . Park et al measured CSA on the planning CT-scans in 962 PC patients receiving adaptive RT with a median prescribed dose of 75.6 Gy [28] .…”

“…The authors found that initial rectal distention was not significantly associated with reduced 5-years biochemical cancer control or grade ≥ 2 genitourinary and gastrointestinal toxicity, and concluded that adaptive IGRT reduces the risk of geographical miss. Silverman et al examined 172 PC patients receiving conformal RT to a total dose of 74 Gy at a median of 72 months follow up [12] . The rectal diameter was measured at the midpoint of the PTV on the planning CT-scan.…”

“…Interfraction displacement of the prostate gland during RT is often observed in response to the variations in rectum and bladder filling, and can range from 0 to 20 mm [1] , [2] , [3] , [4] , [5] , [6] , [7] . Accordingly, rectal volume variation (RVV) during RT may increase the risk of biochemical and local failure [8] , [9] , [10] , [11] , [12] , [13] . Moreover, the rectal volume (RV) receiving ≥ 60 Gy is associated with increased risk of grade ≥ 2 late rectal toxicity or rectal bleeding and can be a limiting factor for dose escalation [14] , [15] , [16] , [17] , [18] , [19] .…”

Reduced Dose Posterior to Prostate Correlates With Increased PSA Progression in Voxel-Based Analysis of 3 Randomized Phase 3 Trials

“…This rectal distension has been associated with increased biochemical and local progression 34 . However, an awareness of rectal distension in the modern era of RT has enabled clinicians to address this effect 35 . In conclusion, it is recommended that particular care is taken when defining margins at the prostate posterior, acknowledging the trade-off between quality of life due to rectal dose and the preferences of clinicians and patients.…”

Feasibility of artificial intelligence-driven interfractional monitoring of organ changes by mega-voltage computed tomography in intensity-modulated radiotherapy of prostate cancer

“…Previous studies have shown that interfractional displacement of the prostate gland can vary from 0 to 20 mm due to the changes in the rectum and bladder filling [1][2][3][4][5][6][7][8]. Changes in rectal volume can increase the risk of biochemical and local failure [1,[9][10][11][12][13][14]. An increase in rectal volume receiving ≥ 60 Gy can elevate the https://doi.org/10.3857/roj.2023.00444 AI-driven organ monitoring by MVCT image risk of grade ≥ 2 rectal toxicity, including rectal bleeding, pain or discomfort during bowel movements, diarrhea, and incontinence [15][16][17][18][19][20].…”