Background

Radiotherapy in combination with androgen deprivation is considered the standard of care in the management of locally advanced prostate cancer. However there still remains controversy over whether whole pelvic radiotherapy (WPRT) with its associated toxicity is more advantageous than prostate only radiotherapy. We report on our initial experience of using Intensity Modulated Radiotherapy (IMRT) in relation to dosimetry and toxicity.

Method

The first 100 patients with high-risk locally advanced prostate cancer receiving WPRT between October 2008 to June 2012, were analyzed. All patients had long-term androgen deprivation (>2yrs) which was commenced neo-adjuvantly. IMRT was delivered using a Simultaneous Integrated Boost (SIB) aiming to treat the pelvis to 50Gy, prostate and seminal vesicles to 64Gy and the prostate alone to 72Gy in 32 fractions. Acute (<3months) and late toxicity (> 6 months) were recorded using RTOG criteria, and correlated with dose volume histogram (DVH) data.

Results

Node positive disease was documented in 11% of the cohort. With a mean follow up of 26 months (SD ± 11.27), no patient discontinued treatment due to toxicity and there were no treatment related deaths. Acute toxicity was self-limiting: bowel RTOG G1-2: 27%, G3-4: 6.5%; and genitourinary toxicity G1-2: 34%, G3-4: 21%. No late bowel or bladder toxicity was observed in 90% and 78% respectively, with greater than grade-3 bowel toxicity of 4% and genitourinary toxicity of 8%. Using IMRT-SIB we were able to meet our departmental rectal, bladder and bowel dose volume constraints in 96%, 72% and 69% 31% respectively. Breach of DVH tolerance, initial rectal or bladder volumes did not predict for the development of toxicity.

Conclusion

Our experience using IMRT/SIB has been favourable, with an acceptable toxicity profile. Static DVH data did not predict for toxicity, and ongoing work will seek to evaluate the role of serial DVH measurements in order to derive dose-volume constraints.