Short-term Hypofractionated Adjuvant Radiotherapy With Helicoidal Tomotherapy After Radical Prostatectomy: Planning Data and Toxicity Results

Article Outline

• Purpose/Objective(s)
• Materials/Methods
• Results
• Conclusions
• Copyright

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Purpose/Objective(s) 

To report on planning and toxicity findings of hypofractionated adjuvant RT with helical Tomotherapy (HTT) after radical retropubic prostatectomy (RRP) for prostate carcinoma (pCa).

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Materials/Methods 

50 consecutive patients (pts) previously submitted to RRP for a pT2R1, pT3a/pT3b (n = 15, 32 and 3, respectively), R0/R1 pN0 pCa, were enrolled from January 2005 to March 2006 in a Phase I-II trial to receive 58 Gy/20 fraction in 4 weeks on the tumoral bed. Applying the linear quadratic model without any repopulation correction, the 2 Gy equivalent dose (EQD2) corresponding to our scheme ranges between 62 and 73 Gy for α/β ranging from 10 to 1.5. Main endpoint of the study was to confirm that this schedule did not increase the risk of grade 2–3 acute/late sequelae and that of biochemical failure when compared to our Institutional experience with conventionally fractionated 3DCRT (68–72 Gy, 1.8 Gy/fr; n = 153 pts). A patient-reported assessment of erectile and urinary functions at baseline, at 3-month follow-up date (3-m), and every 6 months thereafter (6-m, 12-m, and so on) was also activated.

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Results 

Concerning planning data, excellent coverage of PTV and sparing of rectum, bladder and femoral heads were reached: the fraction of PTV receiving a dose >55 Gy was between 96% and 99% and Dmax ranged between 59 and 63 Gy. The sparing of the rectum was particularly relevant: Dmean ranged between 21 and 31 Gy; median value of V40 was 25%. Median follow-up was 21 months (range 11–27). Acute G2-3 genitourinary (GU) RTOG toxicities and acute G2 upper gastrointestinal sequelae (uGI) were similar (GU 14% vs 16%; uGI 4% vs 7%) in HTT and 3DCRT groups, respectively; acute G2 proctitis were 0% vs 9% in HTT and 3DCRT group (p < 0.05), respectively. Similarly, late Grade ≥2 GI sequelae were 0% vs 8.5% (p < 0.05). Concerning late GU sequelae, there were two Grade 2 and four Grade 3 (urethral stricture requiring dilatation) RTOG toxicities after HTT: the cumulative risk of Grade ≥2 late GU toxicity (12%) was similar to that observed in the 3DCRT group (21/153, 14%; dilatation for urethral stricture in 12/153, 8%). Thus far, the crude incidence of urethral stricture requiring dilatation after hypofractionated HTT (8%) seems comparable to that reported after surgery alone. The ANOVA demonstrated that IIEF-erectile function domain score was not significantly decreased throughout the follow-up dates (4.3 ± 5.3 vs 4.1 ± 6.3 vs 2.1 ± 2.0 vs 10.9 ± 8.8, respectively at baseline, at 3-m, at 6-m, and at 12-m of follow-up; F = 2.296; p = 0.07). Similarly, IPSS values were not significantly increased during the same 12-m period (14.3 ± 8.2 vs 13.4 ± 8.8 vs 8.4 ± 4.7 vs 13.8 ± 8.5, respectively at baseline, 3-m, 6-m, 12-m follow-up; F = 1.995; p = 0.12).

At the moment of the present analysis, all pts are bNED.

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Conclusions 

A moderately hypofractionated regimen (58 Gy/20 fractions) with HTT post-RRP is feasible and safe. Grade 2 acute and late proctitis were significantly reduced compared to our high-dose conventionally fractionated 3DCRT experience.