Whole pelvis versus prostate only 3d-conformal radiotherapy in patients with prostate cancer: A retrospective comparison

Aim: The role of elective irradiation of pelvic lymph nodes is an issue that continues to be hotly debated in the radiotherapy treatment of prostate cancer. Our retrospective study aims to compare whole pelvis radiotherapy (WPRT) and prostate only radiotherapy (PORT) as regards prognostic factors, toxicities and dosimetric aspects. Patients and Methods: From October 2006 to February 2011, 220 men affected by prostate cancer underwent radical radiotherapy at the Radiotherapy Department in Foggia. They were treated with multiple 10- 18MV beams and three-dimensional conformal techniques. PORT included the entire prostate with or without seminal vescicles. WPRT included also bilateral obturator, external iliac, internal iliac and presacral nodal regions. PORT doses ranged between 68 and 80Gy. WPRT doses ranged between 44 and 50Gy and were followed by a boost on the prostate volume. For each patient, age, pre-treatment PSA, Gleason score and radiation doses were recorded. Toxicity was assessed according to the time of onset (acute or late toxicity) and the organs at risk involved (genitourinary or rectal and intestinal toxicity); the EORT/RTOG scales were used. Results: Median and minimum follow-up were 36 and 12 months, respectively. Regardless of risk classification, 159 patients (pts) underwent PORT and 61 WPRT. There was a strong association between class of risk and irradiated volumes (p<0.01) and a very significant difference of Gleason score and pre-treatment PSA values between PORT and WPRT groups (p<0.01): PSA and Gleason score were important risk factors guiding radiation oncologists to WPRT. On the contrary, there was no age difference in PORT and WPRT groups (p=0.5): age at diagnosis did not show to be a variable according to which pts were referred for WPRT or PORT. As regards total radiation doses, a difference between the two groups was outlined (p=0.01): when tissues have already received a considerable proportion of dose during irradiation of the pelvis, it is more difficult to deliver high doses to the prostate remaining within tolerance constraints for organs at risk. By analyzing the various types of toxicity, it was noted that 59% of pts undergoing PORT had acute toxicity vs. 64% of pts undergoing WPRT (p=0.51), 11% of pts who underwent PORT manifested late toxicity vs. 10% of pts receiving WPRT (p=0.75), 49% of pts undergoing PORT complained disorders of the urinary sphere vs. 47% of pts that received WPRT (p=0.84), 17% of pts receiving PORT reported rectal or intestinal side-effects vs. 31% of pts that received WPRT (p=0.02): this association between intestinal toxicity and WPRT can be easily explained by the greater portion of bowel exposed to radiation during WPRT (p<0.01). Because of the long natural history of disease and the short follow-up, our series does not allow to draw results about the effectiveness of WPRT vs. PORT. Discussion and Conclusion: Arguments exist for and against the use of prophilactic irradiation of pelvic lymph nodes in prostate cancer management. Our series shows that WPRT and PORT are two therapeutic alternatives routinely used in the radiation treatment of pts with intermediate-high risk prostate cancer. However the final answer on WPRT is not known and requires further studies. Meanwhile, on the one hand radiation oncologist should consider the ease of execution of PORT, the lower intestinal toxicity expected from PORT and its possibility of delivering a higher dose to the prostate when a 3D-conformal technique is used; on the other hand WPRT should be taken into account with the worsening of prognostic factors, especially pre-treatment PSA and Gleason score. A large and homogeneous randomized trial will clarify the usefulness of pelvic irradiation in selected patients with clinically localized prostate cancer.