From two-dimensional to three-dimensional conformal radiotherapy in prostate cancer: An Indian experience.

Background: Sparse data from India are available regarding the outcome of prostate cancer treatment. We report our experience in treating prostate cancer with radiotherapy (RT). Materials and Methods: This study included 159 men with locally advanced cancer treated with RT with or without hormone therapy between 1984 and 2004. The median RT dose was 70 Gy over 35 fractions. Eighty-five patients received whole pelvic RT and prostate boost, and 74 patients were treated with 3-dimensional conformal radiotherapy (3DCRT) to prostate and seminal vesicles alone. Results: The median follow-up was 25 months and the freedom from biochemical failure for all the patients at 5 years was 76%, disease-free survival (DFS) 59.1%, and overall survival (OAS) was 70.1%. The risk stratification (91% vs 52%, P < 0.03) and RT dose (72.8% for dose > 66 Gy vs 43.5% for dose < 66 Gy; P = 0.01) affected the DFS. DFS at 5 years was better in the group receiving 3DCRT to prostate and seminal vesicles (78% vs 51.5%; P = 0.001) and was reflected in OAS as well (P = 0.01). Conclusion: CRT technique with dose escalation results in significant benefit in DFS and OAS in locally advanced prostate cancer.

Prostate helical tomotherapy: a semi-empirical estimation of the scaling factor based on 2D approximating field

In Helical Tomotherapy [HT], the scaling factor [SF] is the time in seconds that each leaf viewing a target would need to be open to deliver the prescribed dose. The SF is patient-specific and is used to calculate the rotational period of the gantry, and the total treatment time [TTT] of the HT. The SF is generally difficult to estimate. Currently, it takes about one hour to fully optimize a prostate HT plan and to calculate the corresponding TTT. The aim of this study is to develop a method for estimation of the SF directly using a patient-specific approximating function. The SFs of ten randomly selected patients were used to build the approximation model. For the entire group of patients the PTV1 ranged from 57 to 396 cm3 for PTV1 margins from 2 to 10 mm. The discrete data for every patient is represented by an individual function, SF=f [kx PTV1]. The values of the function were rescaled to a special unit which represents the target volume irradiated with the prescribed dose per second. The values were normalized with two "geometric" parameters, namely, the target-to-target and the body-to-body ratios. After the normalization, the function for every patient was ordered in the file by the volume of the prostate and seminal vesicles. For prostate HT planning, it was found that the planning target volume [PTV1] has a higher impact on the SF values than the size of the patient's bodies. The function SF=f [kxPTV1] was found smooth and continuous over the given interval. The rescaled and normalized functions for all patients were represented as delimiters of a 2D field. The method proposed for determination of the SF and TTT for HT prostate planning covers PTV1 of four margins and a volume of prostate and seminal vesicles ranging from 42.8 to 161 cm3. Using these approximations, the TTTs for a second group of patients were determined in several minutes with deviation ranging from -2.8% to +7.1% compared to that of the TTTs calculated using the HT planning system